| 1 | @c -*-texinfo-*- |
| 2 | @c This is part of the GNU Emacs Lisp Reference Manual. |
| 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
| 4 | @c Free Software Foundation, Inc. |
| 5 | @c See the file elisp.texi for copying conditions. |
| 6 | @setfilename ../info/processes |
| 7 | @node Processes, Display, Abbrevs, Top |
| 8 | @chapter Processes |
| 9 | @cindex child process |
| 10 | @cindex parent process |
| 11 | @cindex subprocess |
| 12 | @cindex process |
| 13 | |
| 14 | In the terminology of operating systems, a @dfn{process} is a space in |
| 15 | which a program can execute. Emacs runs in a process. Emacs Lisp |
| 16 | programs can invoke other programs in processes of their own. These are |
| 17 | called @dfn{subprocesses} or @dfn{child processes} of the Emacs process, |
| 18 | which is their @dfn{parent process}. |
| 19 | |
| 20 | A subprocess of Emacs may be @dfn{synchronous} or @dfn{asynchronous}, |
| 21 | depending on how it is created. When you create a synchronous |
| 22 | subprocess, the Lisp program waits for the subprocess to terminate |
| 23 | before continuing execution. When you create an asynchronous |
| 24 | subprocess, it can run in parallel with the Lisp program. This kind of |
| 25 | subprocess is represented within Emacs by a Lisp object which is also |
| 26 | called a ``process''. Lisp programs can use this object to communicate |
| 27 | with the subprocess or to control it. For example, you can send |
| 28 | signals, obtain status information, receive output from the process, or |
| 29 | send input to it. |
| 30 | |
| 31 | @defun processp object |
| 32 | This function returns @code{t} if @var{object} is a process, |
| 33 | @code{nil} otherwise. |
| 34 | @end defun |
| 35 | |
| 36 | @menu |
| 37 | * Subprocess Creation:: Functions that start subprocesses. |
| 38 | * Shell Arguments:: Quoting an argument to pass it to a shell. |
| 39 | * Synchronous Processes:: Details of using synchronous subprocesses. |
| 40 | * Asynchronous Processes:: Starting up an asynchronous subprocess. |
| 41 | * Deleting Processes:: Eliminating an asynchronous subprocess. |
| 42 | * Process Information:: Accessing run-status and other attributes. |
| 43 | * Input to Processes:: Sending input to an asynchronous subprocess. |
| 44 | * Signals to Processes:: Stopping, continuing or interrupting |
| 45 | an asynchronous subprocess. |
| 46 | * Output from Processes:: Collecting output from an asynchronous subprocess. |
| 47 | * Sentinels:: Sentinels run when process run-status changes. |
| 48 | * Query Before Exit:: Whether to query if exiting will kill a process. |
| 49 | * Transaction Queues:: Transaction-based communication with subprocesses. |
| 50 | * Network:: Opening network connections. |
| 51 | * Network Servers:: Network servers let Emacs accept net connections. |
| 52 | * Datagrams:: |
| 53 | * Low-Level Network:: Lower-level but more general function |
| 54 | to create connections and servers. |
| 55 | @end menu |
| 56 | |
| 57 | @node Subprocess Creation |
| 58 | @section Functions that Create Subprocesses |
| 59 | |
| 60 | There are three functions that create a new subprocess in which to run |
| 61 | a program. One of them, @code{start-process}, creates an asynchronous |
| 62 | process and returns a process object (@pxref{Asynchronous Processes}). |
| 63 | The other two, @code{call-process} and @code{call-process-region}, |
| 64 | create a synchronous process and do not return a process object |
| 65 | (@pxref{Synchronous Processes}). |
| 66 | |
| 67 | Synchronous and asynchronous processes are explained in the following |
| 68 | sections. Since the three functions are all called in a similar |
| 69 | fashion, their common arguments are described here. |
| 70 | |
| 71 | @cindex execute program |
| 72 | @cindex @code{PATH} environment variable |
| 73 | @cindex @code{HOME} environment variable |
| 74 | In all cases, the function's @var{program} argument specifies the |
| 75 | program to be run. An error is signaled if the file is not found or |
| 76 | cannot be executed. If the file name is relative, the variable |
| 77 | @code{exec-path} contains a list of directories to search. Emacs |
| 78 | initializes @code{exec-path} when it starts up, based on the value of |
| 79 | the environment variable @code{PATH}. The standard file name |
| 80 | constructs, @samp{~}, @samp{.}, and @samp{..}, are interpreted as |
| 81 | usual in @code{exec-path}, but environment variable substitutions |
| 82 | (@samp{$HOME}, etc.) are not recognized; use |
| 83 | @code{substitute-in-file-name} to perform them (@pxref{File Name |
| 84 | Expansion}). @code{nil} in this list refers to |
| 85 | @code{default-directory}. |
| 86 | |
| 87 | Executing a program can also try adding suffixes to the specified |
| 88 | name: |
| 89 | |
| 90 | @defvar exec-suffixes |
| 91 | This variable is a list of suffixes (strings) to try adding to the |
| 92 | specified program file name. The list should include @code{""} if you |
| 93 | want the name to be tried exactly as specified. The default value is |
| 94 | system-dependent. |
| 95 | @end defvar |
| 96 | |
| 97 | @strong{Please note:} The argument @var{program} contains only the |
| 98 | name of the program; it may not contain any command-line arguments. You |
| 99 | must use @var{args} to provide those. |
| 100 | |
| 101 | Each of the subprocess-creating functions has a @var{buffer-or-name} |
| 102 | argument which specifies where the standard output from the program will |
| 103 | go. It should be a buffer or a buffer name; if it is a buffer name, |
| 104 | that will create the buffer if it does not already exist. It can also |
| 105 | be @code{nil}, which says to discard the output unless a filter function |
| 106 | handles it. (@xref{Filter Functions}, and @ref{Read and Print}.) |
| 107 | Normally, you should avoid having multiple processes send output to the |
| 108 | same buffer because their output would be intermixed randomly. |
| 109 | |
| 110 | @cindex program arguments |
| 111 | All three of the subprocess-creating functions have a @code{&rest} |
| 112 | argument, @var{args}. The @var{args} must all be strings, and they are |
| 113 | supplied to @var{program} as separate command line arguments. Wildcard |
| 114 | characters and other shell constructs have no special meanings in these |
| 115 | strings, since the strings are passed directly to the specified program. |
| 116 | |
| 117 | The subprocess gets its current directory from the value of |
| 118 | @code{default-directory} (@pxref{File Name Expansion}). |
| 119 | |
| 120 | @cindex environment variables, subprocesses |
| 121 | The subprocess inherits its environment from Emacs, but you can |
| 122 | specify overrides for it with @code{process-environment}. @xref{System |
| 123 | Environment}. |
| 124 | |
| 125 | @defvar exec-directory |
| 126 | @pindex movemail |
| 127 | The value of this variable is a string, the name of a directory that |
| 128 | contains programs that come with GNU Emacs, programs intended for Emacs |
| 129 | to invoke. The program @code{movemail} is an example of such a program; |
| 130 | Rmail uses it to fetch new mail from an inbox. |
| 131 | @end defvar |
| 132 | |
| 133 | @defopt exec-path |
| 134 | The value of this variable is a list of directories to search for |
| 135 | programs to run in subprocesses. Each element is either the name of a |
| 136 | directory (i.e., a string), or @code{nil}, which stands for the default |
| 137 | directory (which is the value of @code{default-directory}). |
| 138 | @cindex program directories |
| 139 | |
| 140 | The value of @code{exec-path} is used by @code{call-process} and |
| 141 | @code{start-process} when the @var{program} argument is not an absolute |
| 142 | file name. |
| 143 | @end defopt |
| 144 | |
| 145 | @node Shell Arguments |
| 146 | @section Shell Arguments |
| 147 | |
| 148 | Lisp programs sometimes need to run a shell and give it a command |
| 149 | that contains file names that were specified by the user. These |
| 150 | programs ought to be able to support any valid file name. But the shell |
| 151 | gives special treatment to certain characters, and if these characters |
| 152 | occur in the file name, they will confuse the shell. To handle these |
| 153 | characters, use the function @code{shell-quote-argument}: |
| 154 | |
| 155 | @defun shell-quote-argument argument |
| 156 | This function returns a string which represents, in shell syntax, |
| 157 | an argument whose actual contents are @var{argument}. It should |
| 158 | work reliably to concatenate the return value into a shell command |
| 159 | and then pass it to a shell for execution. |
| 160 | |
| 161 | Precisely what this function does depends on your operating system. The |
| 162 | function is designed to work with the syntax of your system's standard |
| 163 | shell; if you use an unusual shell, you will need to redefine this |
| 164 | function. |
| 165 | |
| 166 | @example |
| 167 | ;; @r{This example shows the behavior on GNU and Unix systems.} |
| 168 | (shell-quote-argument "foo > bar") |
| 169 | @result{} "foo\\ \\>\\ bar" |
| 170 | |
| 171 | ;; @r{This example shows the behavior on MS-DOS and MS-Windows systems.} |
| 172 | (shell-quote-argument "foo > bar") |
| 173 | @result{} "\"foo > bar\"" |
| 174 | @end example |
| 175 | |
| 176 | Here's an example of using @code{shell-quote-argument} to construct |
| 177 | a shell command: |
| 178 | |
| 179 | @example |
| 180 | (concat "diff -c " |
| 181 | (shell-quote-argument oldfile) |
| 182 | " " |
| 183 | (shell-quote-argument newfile)) |
| 184 | @end example |
| 185 | @end defun |
| 186 | |
| 187 | @node Synchronous Processes |
| 188 | @section Creating a Synchronous Process |
| 189 | @cindex synchronous subprocess |
| 190 | |
| 191 | After a @dfn{synchronous process} is created, Emacs waits for the |
| 192 | process to terminate before continuing. Starting Dired on GNU or |
| 193 | Unix@footnote{On other systems, Emacs uses a Lisp emulation of |
| 194 | @code{ls}; see @ref{Contents of Directories}.} is an example of this: it |
| 195 | runs @code{ls} in a synchronous process, then modifies the output |
| 196 | slightly. Because the process is synchronous, the entire directory |
| 197 | listing arrives in the buffer before Emacs tries to do anything with it. |
| 198 | |
| 199 | While Emacs waits for the synchronous subprocess to terminate, the |
| 200 | user can quit by typing @kbd{C-g}. The first @kbd{C-g} tries to kill |
| 201 | the subprocess with a @code{SIGINT} signal; but it waits until the |
| 202 | subprocess actually terminates before quitting. If during that time the |
| 203 | user types another @kbd{C-g}, that kills the subprocess instantly with |
| 204 | @code{SIGKILL} and quits immediately (except on MS-DOS, where killing |
| 205 | other processes doesn't work). @xref{Quitting}. |
| 206 | |
| 207 | The synchronous subprocess functions return an indication of how the |
| 208 | process terminated. |
| 209 | |
| 210 | The output from a synchronous subprocess is generally decoded using a |
| 211 | coding system, much like text read from a file. The input sent to a |
| 212 | subprocess by @code{call-process-region} is encoded using a coding |
| 213 | system, much like text written into a file. @xref{Coding Systems}. |
| 214 | |
| 215 | @defun call-process program &optional infile destination display &rest args |
| 216 | This function calls @var{program} in a separate process and waits for |
| 217 | it to finish. |
| 218 | |
| 219 | The standard input for the process comes from file @var{infile} if |
| 220 | @var{infile} is not @code{nil}, and from the null device otherwise. |
| 221 | The argument @var{destination} says where to put the process output. |
| 222 | Here are the possibilities: |
| 223 | |
| 224 | @table @asis |
| 225 | @item a buffer |
| 226 | Insert the output in that buffer, before point. This includes both the |
| 227 | standard output stream and the standard error stream of the process. |
| 228 | |
| 229 | @item a string |
| 230 | Insert the output in a buffer with that name, before point. |
| 231 | |
| 232 | @item @code{t} |
| 233 | Insert the output in the current buffer, before point. |
| 234 | |
| 235 | @item @code{nil} |
| 236 | Discard the output. |
| 237 | |
| 238 | @item 0 |
| 239 | Discard the output, and return @code{nil} immediately without waiting |
| 240 | for the subprocess to finish. |
| 241 | |
| 242 | In this case, the process is not truly synchronous, since it can run in |
| 243 | parallel with Emacs; but you can think of it as synchronous in that |
| 244 | Emacs is essentially finished with the subprocess as soon as this |
| 245 | function returns. |
| 246 | |
| 247 | MS-DOS doesn't support asynchronous subprocesses, so this option doesn't |
| 248 | work there. |
| 249 | |
| 250 | @item @code{(@var{real-destination} @var{error-destination})} |
| 251 | Keep the standard output stream separate from the standard error stream; |
| 252 | deal with the ordinary output as specified by @var{real-destination}, |
| 253 | and dispose of the error output according to @var{error-destination}. |
| 254 | If @var{error-destination} is @code{nil}, that means to discard the |
| 255 | error output, @code{t} means mix it with the ordinary output, and a |
| 256 | string specifies a file name to redirect error output into. |
| 257 | |
| 258 | You can't directly specify a buffer to put the error output in; that is |
| 259 | too difficult to implement. But you can achieve this result by sending |
| 260 | the error output to a temporary file and then inserting the file into a |
| 261 | buffer. |
| 262 | @end table |
| 263 | |
| 264 | If @var{display} is non-@code{nil}, then @code{call-process} redisplays |
| 265 | the buffer as output is inserted. (However, if the coding system chosen |
| 266 | for decoding output is @code{undecided}, meaning deduce the encoding |
| 267 | from the actual data, then redisplay sometimes cannot continue once |
| 268 | non-@acronym{ASCII} characters are encountered. There are fundamental |
| 269 | reasons why it is hard to fix this; see @ref{Output from Processes}.) |
| 270 | |
| 271 | Otherwise the function @code{call-process} does no redisplay, and the |
| 272 | results become visible on the screen only when Emacs redisplays that |
| 273 | buffer in the normal course of events. |
| 274 | |
| 275 | The remaining arguments, @var{args}, are strings that specify command |
| 276 | line arguments for the program. |
| 277 | |
| 278 | The value returned by @code{call-process} (unless you told it not to |
| 279 | wait) indicates the reason for process termination. A number gives the |
| 280 | exit status of the subprocess; 0 means success, and any other value |
| 281 | means failure. If the process terminated with a signal, |
| 282 | @code{call-process} returns a string describing the signal. |
| 283 | |
| 284 | In the examples below, the buffer @samp{foo} is current. |
| 285 | |
| 286 | @smallexample |
| 287 | @group |
| 288 | (call-process "pwd" nil t) |
| 289 | @result{} 0 |
| 290 | |
| 291 | ---------- Buffer: foo ---------- |
| 292 | /usr/user/lewis/manual |
| 293 | ---------- Buffer: foo ---------- |
| 294 | @end group |
| 295 | |
| 296 | @group |
| 297 | (call-process "grep" nil "bar" nil "lewis" "/etc/passwd") |
| 298 | @result{} 0 |
| 299 | |
| 300 | ---------- Buffer: bar ---------- |
| 301 | lewis:5LTsHm66CSWKg:398:21:Bil Lewis:/user/lewis:/bin/csh |
| 302 | |
| 303 | ---------- Buffer: bar ---------- |
| 304 | @end group |
| 305 | @end smallexample |
| 306 | |
| 307 | Here is a good example of the use of @code{call-process}, which used to |
| 308 | be found in the definition of @code{insert-directory}: |
| 309 | |
| 310 | @smallexample |
| 311 | @group |
| 312 | (call-process insert-directory-program nil t nil @var{switches} |
| 313 | (if full-directory-p |
| 314 | (concat (file-name-as-directory file) ".") |
| 315 | file)) |
| 316 | @end group |
| 317 | @end smallexample |
| 318 | @end defun |
| 319 | |
| 320 | @defun process-file program &optional infile buffer display &rest args |
| 321 | This function processes files synchronously in a separate process. It |
| 322 | is similar to @code{call-process} but may invoke a file handler based |
| 323 | on the value of the variable @code{default-directory}. The current |
| 324 | working directory of the subprocess is @code{default-directory}. |
| 325 | |
| 326 | The arguments are handled in almost the same way as for |
| 327 | @code{call-process}, with the following differences: |
| 328 | |
| 329 | Some file handlers may not support all combinations and forms of the |
| 330 | arguments @var{infile}, @var{buffer}, and @var{display}. For example, |
| 331 | some file handlers might behave as if @var{display} were @code{nil}, |
| 332 | regardless of the value actually passed. As another example, some |
| 333 | file handlers might not support separating standard output and error |
| 334 | output by way of the @var{buffer} argument. |
| 335 | |
| 336 | If a file handler is invoked, it determines the program to run based |
| 337 | on the first argument @var{program}. For instance, consider that a |
| 338 | handler for remote files is invoked. Then the path that is used for |
| 339 | searching the program might be different than @code{exec-path}. |
| 340 | |
| 341 | The second argument @var{infile} may invoke a file handler. The file |
| 342 | handler could be different from the handler chosen for the |
| 343 | @code{process-file} function itself. (For example, |
| 344 | @code{default-directory} could be on a remote host, whereas |
| 345 | @var{infile} is on another remote host. Or @code{default-directory} |
| 346 | could be non-special, whereas @var{infile} is on a remote host.) |
| 347 | |
| 348 | If @var{buffer} has the form @code{(@var{real-destination} |
| 349 | @var{error-destination})}, and @var{error-destination} names a file, |
| 350 | then the same remarks as for @var{infile} apply. |
| 351 | |
| 352 | The remaining arguments (@var{args}) will be passed to the process |
| 353 | verbatim. Emacs is not involved in processing file names that are |
| 354 | present in @var{args}. To avoid confusion, it may be best to avoid |
| 355 | absolute file names in @var{args}, but rather to specify all file |
| 356 | names as relative to @code{default-directory}. The function |
| 357 | @code{file-relative-name} is useful for constructing such relative |
| 358 | file names. |
| 359 | @end defun |
| 360 | |
| 361 | @defun call-process-region start end program &optional delete destination display &rest args |
| 362 | This function sends the text from @var{start} to @var{end} as |
| 363 | standard input to a process running @var{program}. It deletes the text |
| 364 | sent if @var{delete} is non-@code{nil}; this is useful when |
| 365 | @var{destination} is @code{t}, to insert the output in the current |
| 366 | buffer in place of the input. |
| 367 | |
| 368 | The arguments @var{destination} and @var{display} control what to do |
| 369 | with the output from the subprocess, and whether to update the display |
| 370 | as it comes in. For details, see the description of |
| 371 | @code{call-process}, above. If @var{destination} is the integer 0, |
| 372 | @code{call-process-region} discards the output and returns @code{nil} |
| 373 | immediately, without waiting for the subprocess to finish (this only |
| 374 | works if asynchronous subprocesses are supported). |
| 375 | |
| 376 | The remaining arguments, @var{args}, are strings that specify command |
| 377 | line arguments for the program. |
| 378 | |
| 379 | The return value of @code{call-process-region} is just like that of |
| 380 | @code{call-process}: @code{nil} if you told it to return without |
| 381 | waiting; otherwise, a number or string which indicates how the |
| 382 | subprocess terminated. |
| 383 | |
| 384 | In the following example, we use @code{call-process-region} to run the |
| 385 | @code{cat} utility, with standard input being the first five characters |
| 386 | in buffer @samp{foo} (the word @samp{input}). @code{cat} copies its |
| 387 | standard input into its standard output. Since the argument |
| 388 | @var{destination} is @code{t}, this output is inserted in the current |
| 389 | buffer. |
| 390 | |
| 391 | @smallexample |
| 392 | @group |
| 393 | ---------- Buffer: foo ---------- |
| 394 | input@point{} |
| 395 | ---------- Buffer: foo ---------- |
| 396 | @end group |
| 397 | |
| 398 | @group |
| 399 | (call-process-region 1 6 "cat" nil t) |
| 400 | @result{} 0 |
| 401 | |
| 402 | ---------- Buffer: foo ---------- |
| 403 | inputinput@point{} |
| 404 | ---------- Buffer: foo ---------- |
| 405 | @end group |
| 406 | @end smallexample |
| 407 | |
| 408 | The @code{shell-command-on-region} command uses |
| 409 | @code{call-process-region} like this: |
| 410 | |
| 411 | @smallexample |
| 412 | @group |
| 413 | (call-process-region |
| 414 | start end |
| 415 | shell-file-name ; @r{Name of program.} |
| 416 | nil ; @r{Do not delete region.} |
| 417 | buffer ; @r{Send output to @code{buffer}.} |
| 418 | nil ; @r{No redisplay during output.} |
| 419 | "-c" command) ; @r{Arguments for the shell.} |
| 420 | @end group |
| 421 | @end smallexample |
| 422 | @end defun |
| 423 | |
| 424 | @defun call-process-shell-command command &optional infile destination display &rest args |
| 425 | This function executes the shell command @var{command} synchronously |
| 426 | in a separate process. The final arguments @var{args} are additional |
| 427 | arguments to add at the end of @var{command}. The other arguments |
| 428 | are handled as in @code{call-process}. |
| 429 | @end defun |
| 430 | |
| 431 | @defun shell-command-to-string command |
| 432 | This function executes @var{command} (a string) as a shell command, |
| 433 | then returns the command's output as a string. |
| 434 | @end defun |
| 435 | |
| 436 | @node Asynchronous Processes |
| 437 | @section Creating an Asynchronous Process |
| 438 | @cindex asynchronous subprocess |
| 439 | |
| 440 | After an @dfn{asynchronous process} is created, Emacs and the subprocess |
| 441 | both continue running immediately. The process thereafter runs |
| 442 | in parallel with Emacs, and the two can communicate with each other |
| 443 | using the functions described in the following sections. However, |
| 444 | communication is only partially asynchronous: Emacs sends data to the |
| 445 | process only when certain functions are called, and Emacs accepts data |
| 446 | from the process only when Emacs is waiting for input or for a time |
| 447 | delay. |
| 448 | |
| 449 | Here we describe how to create an asynchronous process. |
| 450 | |
| 451 | @defun start-process name buffer-or-name program &rest args |
| 452 | This function creates a new asynchronous subprocess and starts the |
| 453 | program @var{program} running in it. It returns a process object that |
| 454 | stands for the new subprocess in Lisp. The argument @var{name} |
| 455 | specifies the name for the process object; if a process with this name |
| 456 | already exists, then @var{name} is modified (by appending @samp{<1>}, |
| 457 | etc.) to be unique. The buffer @var{buffer-or-name} is the buffer to |
| 458 | associate with the process. |
| 459 | |
| 460 | The remaining arguments, @var{args}, are strings that specify command |
| 461 | line arguments for the program. |
| 462 | |
| 463 | In the example below, the first process is started and runs (rather, |
| 464 | sleeps) for 100 seconds. Meanwhile, the second process is started, and |
| 465 | given the name @samp{my-process<1>} for the sake of uniqueness. It |
| 466 | inserts the directory listing at the end of the buffer @samp{foo}, |
| 467 | before the first process finishes. Then it finishes, and a message to |
| 468 | that effect is inserted in the buffer. Much later, the first process |
| 469 | finishes, and another message is inserted in the buffer for it. |
| 470 | |
| 471 | @smallexample |
| 472 | @group |
| 473 | (start-process "my-process" "foo" "sleep" "100") |
| 474 | @result{} #<process my-process> |
| 475 | @end group |
| 476 | |
| 477 | @group |
| 478 | (start-process "my-process" "foo" "ls" "-l" "/user/lewis/bin") |
| 479 | @result{} #<process my-process<1>> |
| 480 | |
| 481 | ---------- Buffer: foo ---------- |
| 482 | total 2 |
| 483 | lrwxrwxrwx 1 lewis 14 Jul 22 10:12 gnuemacs --> /emacs |
| 484 | -rwxrwxrwx 1 lewis 19 Jul 30 21:02 lemon |
| 485 | |
| 486 | Process my-process<1> finished |
| 487 | |
| 488 | Process my-process finished |
| 489 | ---------- Buffer: foo ---------- |
| 490 | @end group |
| 491 | @end smallexample |
| 492 | @end defun |
| 493 | |
| 494 | @defun start-process-shell-command name buffer-or-name command &rest command-args |
| 495 | This function is like @code{start-process} except that it uses a shell |
| 496 | to execute the specified command. The argument @var{command} is a shell |
| 497 | command name, and @var{command-args} are the arguments for the shell |
| 498 | command. The variable @code{shell-file-name} specifies which shell to |
| 499 | use. |
| 500 | |
| 501 | The point of running a program through the shell, rather than directly |
| 502 | with @code{start-process}, is so that you can employ shell features such |
| 503 | as wildcards in the arguments. It follows that if you include an |
| 504 | arbitrary user-specified arguments in the command, you should quote it |
| 505 | with @code{shell-quote-argument} first, so that any special shell |
| 506 | characters do @emph{not} have their special shell meanings. @xref{Shell |
| 507 | Arguments}. |
| 508 | @end defun |
| 509 | |
| 510 | @defvar process-connection-type |
| 511 | @cindex pipes |
| 512 | @cindex @acronym{PTY}s |
| 513 | This variable controls the type of device used to communicate with |
| 514 | asynchronous subprocesses. If it is non-@code{nil}, then @acronym{PTY}s are |
| 515 | used, when available. Otherwise, pipes are used. |
| 516 | |
| 517 | @acronym{PTY}s are usually preferable for processes visible to the user, as |
| 518 | in Shell mode, because they allow job control (@kbd{C-c}, @kbd{C-z}, |
| 519 | etc.) to work between the process and its children, whereas pipes do |
| 520 | not. For subprocesses used for internal purposes by programs, it is |
| 521 | often better to use a pipe, because they are more efficient. In |
| 522 | addition, the total number of @acronym{PTY}s is limited on many systems and |
| 523 | it is good not to waste them. |
| 524 | |
| 525 | The value of @code{process-connection-type} takes effect when |
| 526 | @code{start-process} is called. So you can specify how to communicate |
| 527 | with one subprocess by binding the variable around the call to |
| 528 | @code{start-process}. |
| 529 | |
| 530 | @smallexample |
| 531 | @group |
| 532 | (let ((process-connection-type nil)) ; @r{Use a pipe.} |
| 533 | (start-process @dots{})) |
| 534 | @end group |
| 535 | @end smallexample |
| 536 | |
| 537 | To determine whether a given subprocess actually got a pipe or a |
| 538 | @acronym{PTY}, use the function @code{process-tty-name} (@pxref{Process |
| 539 | Information}). |
| 540 | @end defvar |
| 541 | |
| 542 | @node Deleting Processes |
| 543 | @section Deleting Processes |
| 544 | @cindex deleting processes |
| 545 | |
| 546 | @dfn{Deleting a process} disconnects Emacs immediately from the |
| 547 | subprocess. Processes are deleted automatically after they terminate, |
| 548 | but not necessarily right away. You can delete a process explicitly |
| 549 | at any time. If you delete a terminated process explicitly before it |
| 550 | is deleted automatically, no harm results. Deleting a running |
| 551 | process sends a signal to terminate it (and its child processes if |
| 552 | any), and calls the process sentinel if it has one. @xref{Sentinels}. |
| 553 | |
| 554 | When a process is deleted, the process object itself continues to |
| 555 | exist as long as other Lisp objects point to it. All the Lisp |
| 556 | primitives that work on process objects accept deleted processes, but |
| 557 | those that do I/O or send signals will report an error. The process |
| 558 | mark continues to point to the same place as before, usually into a |
| 559 | buffer where output from the process was being inserted. |
| 560 | |
| 561 | @defopt delete-exited-processes |
| 562 | This variable controls automatic deletion of processes that have |
| 563 | terminated (due to calling @code{exit} or to a signal). If it is |
| 564 | @code{nil}, then they continue to exist until the user runs |
| 565 | @code{list-processes}. Otherwise, they are deleted immediately after |
| 566 | they exit. |
| 567 | @end defopt |
| 568 | |
| 569 | @defun delete-process process |
| 570 | This function deletes a process, killing it with a @code{SIGKILL} |
| 571 | signal. The argument may be a process, the name of a process, a |
| 572 | buffer, or the name of a buffer. (A buffer or buffer-name stands for |
| 573 | the process that @code{get-buffer-process} returns.) Calling |
| 574 | @code{delete-process} on a running process terminates it, updates the |
| 575 | process status, and runs the sentinel (if any) immediately. If the |
| 576 | process has already terminated, calling @code{delete-process} has no |
| 577 | effect on its status, or on the running of its sentinel (which will |
| 578 | happen sooner or later). |
| 579 | |
| 580 | @smallexample |
| 581 | @group |
| 582 | (delete-process "*shell*") |
| 583 | @result{} nil |
| 584 | @end group |
| 585 | @end smallexample |
| 586 | @end defun |
| 587 | |
| 588 | @node Process Information |
| 589 | @section Process Information |
| 590 | |
| 591 | Several functions return information about processes. |
| 592 | @code{list-processes} is provided for interactive use. |
| 593 | |
| 594 | @deffn Command list-processes &optional query-only |
| 595 | This command displays a listing of all living processes. In addition, |
| 596 | it finally deletes any process whose status was @samp{Exited} or |
| 597 | @samp{Signaled}. It returns @code{nil}. |
| 598 | |
| 599 | If @var{query-only} is non-@code{nil} then it lists only processes |
| 600 | whose query flag is non-@code{nil}. @xref{Query Before Exit}. |
| 601 | @end deffn |
| 602 | |
| 603 | @defun process-list |
| 604 | This function returns a list of all processes that have not been deleted. |
| 605 | |
| 606 | @smallexample |
| 607 | @group |
| 608 | (process-list) |
| 609 | @result{} (#<process display-time> #<process shell>) |
| 610 | @end group |
| 611 | @end smallexample |
| 612 | @end defun |
| 613 | |
| 614 | @defun get-process name |
| 615 | This function returns the process named @var{name}, or @code{nil} if |
| 616 | there is none. An error is signaled if @var{name} is not a string. |
| 617 | |
| 618 | @smallexample |
| 619 | @group |
| 620 | (get-process "shell") |
| 621 | @result{} #<process shell> |
| 622 | @end group |
| 623 | @end smallexample |
| 624 | @end defun |
| 625 | |
| 626 | @defun process-command process |
| 627 | This function returns the command that was executed to start |
| 628 | @var{process}. This is a list of strings, the first string being the |
| 629 | program executed and the rest of the strings being the arguments that |
| 630 | were given to the program. |
| 631 | |
| 632 | @smallexample |
| 633 | @group |
| 634 | (process-command (get-process "shell")) |
| 635 | @result{} ("/bin/csh" "-i") |
| 636 | @end group |
| 637 | @end smallexample |
| 638 | @end defun |
| 639 | |
| 640 | @defun process-id process |
| 641 | This function returns the @acronym{PID} of @var{process}. This is an |
| 642 | integer that distinguishes the process @var{process} from all other |
| 643 | processes running on the same computer at the current time. The |
| 644 | @acronym{PID} of a process is chosen by the operating system kernel when the |
| 645 | process is started and remains constant as long as the process exists. |
| 646 | @end defun |
| 647 | |
| 648 | @defun process-name process |
| 649 | This function returns the name of @var{process}. |
| 650 | @end defun |
| 651 | |
| 652 | @defun process-status process-name |
| 653 | This function returns the status of @var{process-name} as a symbol. |
| 654 | The argument @var{process-name} must be a process, a buffer, a |
| 655 | process name (string) or a buffer name (string). |
| 656 | |
| 657 | The possible values for an actual subprocess are: |
| 658 | |
| 659 | @table @code |
| 660 | @item run |
| 661 | for a process that is running. |
| 662 | @item stop |
| 663 | for a process that is stopped but continuable. |
| 664 | @item exit |
| 665 | for a process that has exited. |
| 666 | @item signal |
| 667 | for a process that has received a fatal signal. |
| 668 | @item open |
| 669 | for a network connection that is open. |
| 670 | @item closed |
| 671 | for a network connection that is closed. Once a connection |
| 672 | is closed, you cannot reopen it, though you might be able to open |
| 673 | a new connection to the same place. |
| 674 | @item connect |
| 675 | for a non-blocking connection that is waiting to complete. |
| 676 | @item failed |
| 677 | for a non-blocking connection that has failed to complete. |
| 678 | @item listen |
| 679 | for a network server that is listening. |
| 680 | @item nil |
| 681 | if @var{process-name} is not the name of an existing process. |
| 682 | @end table |
| 683 | |
| 684 | @smallexample |
| 685 | @group |
| 686 | (process-status "shell") |
| 687 | @result{} run |
| 688 | @end group |
| 689 | @group |
| 690 | (process-status (get-buffer "*shell*")) |
| 691 | @result{} run |
| 692 | @end group |
| 693 | @group |
| 694 | x |
| 695 | @result{} #<process xx<1>> |
| 696 | (process-status x) |
| 697 | @result{} exit |
| 698 | @end group |
| 699 | @end smallexample |
| 700 | |
| 701 | For a network connection, @code{process-status} returns one of the symbols |
| 702 | @code{open} or @code{closed}. The latter means that the other side |
| 703 | closed the connection, or Emacs did @code{delete-process}. |
| 704 | @end defun |
| 705 | |
| 706 | @defun process-exit-status process |
| 707 | This function returns the exit status of @var{process} or the signal |
| 708 | number that killed it. (Use the result of @code{process-status} to |
| 709 | determine which of those it is.) If @var{process} has not yet |
| 710 | terminated, the value is 0. |
| 711 | @end defun |
| 712 | |
| 713 | @defun process-tty-name process |
| 714 | This function returns the terminal name that @var{process} is using for |
| 715 | its communication with Emacs---or @code{nil} if it is using pipes |
| 716 | instead of a terminal (see @code{process-connection-type} in |
| 717 | @ref{Asynchronous Processes}). |
| 718 | @end defun |
| 719 | |
| 720 | @defun process-coding-system process |
| 721 | @anchor{Coding systems for a subprocess} |
| 722 | This function returns a cons cell describing the coding systems in use |
| 723 | for decoding output from @var{process} and for encoding input to |
| 724 | @var{process} (@pxref{Coding Systems}). The value has this form: |
| 725 | |
| 726 | @example |
| 727 | (@var{coding-system-for-decoding} . @var{coding-system-for-encoding}) |
| 728 | @end example |
| 729 | @end defun |
| 730 | |
| 731 | @defun set-process-coding-system process &optional decoding-system encoding-system |
| 732 | This function specifies the coding systems to use for subsequent output |
| 733 | from and input to @var{process}. It will use @var{decoding-system} to |
| 734 | decode subprocess output, and @var{encoding-system} to encode subprocess |
| 735 | input. |
| 736 | @end defun |
| 737 | |
| 738 | Every process also has a property list that you can use to store |
| 739 | miscellaneous values associated with the process. |
| 740 | |
| 741 | @defun process-get process propname |
| 742 | This function returns the value of the @var{propname} property |
| 743 | of @var{process}. |
| 744 | @end defun |
| 745 | |
| 746 | @defun process-put process propname value |
| 747 | This function sets the value of the @var{propname} property |
| 748 | of @var{process} to @var{value}. |
| 749 | @end defun |
| 750 | |
| 751 | @defun process-plist process |
| 752 | This function returns the process plist of @var{process}. |
| 753 | @end defun |
| 754 | |
| 755 | @defun set-process-plist process plist |
| 756 | This function sets the process plist of @var{process} to @var{plist}. |
| 757 | @end defun |
| 758 | |
| 759 | @node Input to Processes |
| 760 | @section Sending Input to Processes |
| 761 | @cindex process input |
| 762 | |
| 763 | Asynchronous subprocesses receive input when it is sent to them by |
| 764 | Emacs, which is done with the functions in this section. You must |
| 765 | specify the process to send input to, and the input data to send. The |
| 766 | data appears on the ``standard input'' of the subprocess. |
| 767 | |
| 768 | Some operating systems have limited space for buffered input in a |
| 769 | @acronym{PTY}. On these systems, Emacs sends an @acronym{EOF} periodically amidst |
| 770 | the other characters, to force them through. For most programs, |
| 771 | these @acronym{EOF}s do no harm. |
| 772 | |
| 773 | Subprocess input is normally encoded using a coding system before the |
| 774 | subprocess receives it, much like text written into a file. You can use |
| 775 | @code{set-process-coding-system} to specify which coding system to use |
| 776 | (@pxref{Process Information}). Otherwise, the coding system comes from |
| 777 | @code{coding-system-for-write}, if that is non-@code{nil}; or else from |
| 778 | the defaulting mechanism (@pxref{Default Coding Systems}). |
| 779 | |
| 780 | Sometimes the system is unable to accept input for that process, |
| 781 | because the input buffer is full. When this happens, the send functions |
| 782 | wait a short while, accepting output from subprocesses, and then try |
| 783 | again. This gives the subprocess a chance to read more of its pending |
| 784 | input and make space in the buffer. It also allows filters, sentinels |
| 785 | and timers to run---so take account of that in writing your code. |
| 786 | |
| 787 | In these functions, the @var{process} argument can be a process or |
| 788 | the name of a process, or a buffer or buffer name (which stands |
| 789 | for a process via @code{get-buffer-process}). @code{nil} means |
| 790 | the current buffer's process. |
| 791 | |
| 792 | @defun process-send-string process string |
| 793 | This function sends @var{process} the contents of @var{string} as |
| 794 | standard input. If it is @code{nil}, the current buffer's process is used. |
| 795 | |
| 796 | The function returns @code{nil}. |
| 797 | |
| 798 | @smallexample |
| 799 | @group |
| 800 | (process-send-string "shell<1>" "ls\n") |
| 801 | @result{} nil |
| 802 | @end group |
| 803 | |
| 804 | |
| 805 | @group |
| 806 | ---------- Buffer: *shell* ---------- |
| 807 | ... |
| 808 | introduction.texi syntax-tables.texi~ |
| 809 | introduction.texi~ text.texi |
| 810 | introduction.txt text.texi~ |
| 811 | ... |
| 812 | ---------- Buffer: *shell* ---------- |
| 813 | @end group |
| 814 | @end smallexample |
| 815 | @end defun |
| 816 | |
| 817 | @defun process-send-region process start end |
| 818 | This function sends the text in the region defined by @var{start} and |
| 819 | @var{end} as standard input to @var{process}. |
| 820 | |
| 821 | An error is signaled unless both @var{start} and @var{end} are |
| 822 | integers or markers that indicate positions in the current buffer. (It |
| 823 | is unimportant which number is larger.) |
| 824 | @end defun |
| 825 | |
| 826 | @defun process-send-eof &optional process |
| 827 | This function makes @var{process} see an end-of-file in its |
| 828 | input. The @acronym{EOF} comes after any text already sent to it. |
| 829 | |
| 830 | The function returns @var{process}. |
| 831 | |
| 832 | @smallexample |
| 833 | @group |
| 834 | (process-send-eof "shell") |
| 835 | @result{} "shell" |
| 836 | @end group |
| 837 | @end smallexample |
| 838 | @end defun |
| 839 | |
| 840 | @defun process-running-child-p process |
| 841 | @tindex process-running-child-p process |
| 842 | This function will tell you whether a subprocess has given control of |
| 843 | its terminal to its own child process. The value is @code{t} if this is |
| 844 | true, or if Emacs cannot tell; it is @code{nil} if Emacs can be certain |
| 845 | that this is not so. |
| 846 | @end defun |
| 847 | |
| 848 | @node Signals to Processes |
| 849 | @section Sending Signals to Processes |
| 850 | @cindex process signals |
| 851 | @cindex sending signals |
| 852 | @cindex signals |
| 853 | |
| 854 | @dfn{Sending a signal} to a subprocess is a way of interrupting its |
| 855 | activities. There are several different signals, each with its own |
| 856 | meaning. The set of signals and their names is defined by the operating |
| 857 | system. For example, the signal @code{SIGINT} means that the user has |
| 858 | typed @kbd{C-c}, or that some analogous thing has happened. |
| 859 | |
| 860 | Each signal has a standard effect on the subprocess. Most signals |
| 861 | kill the subprocess, but some stop or resume execution instead. Most |
| 862 | signals can optionally be handled by programs; if the program handles |
| 863 | the signal, then we can say nothing in general about its effects. |
| 864 | |
| 865 | You can send signals explicitly by calling the functions in this |
| 866 | section. Emacs also sends signals automatically at certain times: |
| 867 | killing a buffer sends a @code{SIGHUP} signal to all its associated |
| 868 | processes; killing Emacs sends a @code{SIGHUP} signal to all remaining |
| 869 | processes. (@code{SIGHUP} is a signal that usually indicates that the |
| 870 | user hung up the phone.) |
| 871 | |
| 872 | Each of the signal-sending functions takes two optional arguments: |
| 873 | @var{process-name} and @var{current-group}. |
| 874 | |
| 875 | The argument @var{process} must be either a process, a process |
| 876 | name, a buffer, a buffer name, or @code{nil}. A buffer or buffer name |
| 877 | stands for a process through @code{get-buffer-process}. @code{nil} |
| 878 | stands for the process associated with the current buffer. An error |
| 879 | is signaled if @var{process} does not identify a process. |
| 880 | |
| 881 | The argument @var{current-group} is a flag that makes a difference |
| 882 | when you are running a job-control shell as an Emacs subprocess. If it |
| 883 | is non-@code{nil}, then the signal is sent to the current process-group |
| 884 | of the terminal that Emacs uses to communicate with the subprocess. If |
| 885 | the process is a job-control shell, this means the shell's current |
| 886 | subjob. If it is @code{nil}, the signal is sent to the process group of |
| 887 | the immediate subprocess of Emacs. If the subprocess is a job-control |
| 888 | shell, this is the shell itself. |
| 889 | |
| 890 | The flag @var{current-group} has no effect when a pipe is used to |
| 891 | communicate with the subprocess, because the operating system does not |
| 892 | support the distinction in the case of pipes. For the same reason, |
| 893 | job-control shells won't work when a pipe is used. See |
| 894 | @code{process-connection-type} in @ref{Asynchronous Processes}. |
| 895 | |
| 896 | @defun interrupt-process &optional process current-group |
| 897 | This function interrupts the process @var{process} by sending the |
| 898 | signal @code{SIGINT}. Outside of Emacs, typing the ``interrupt |
| 899 | character'' (normally @kbd{C-c} on some systems, and @code{DEL} on |
| 900 | others) sends this signal. When the argument @var{current-group} is |
| 901 | non-@code{nil}, you can think of this function as ``typing @kbd{C-c}'' |
| 902 | on the terminal by which Emacs talks to the subprocess. |
| 903 | @end defun |
| 904 | |
| 905 | @defun kill-process &optional process current-group |
| 906 | This function kills the process @var{process} by sending the |
| 907 | signal @code{SIGKILL}. This signal kills the subprocess immediately, |
| 908 | and cannot be handled by the subprocess. |
| 909 | @end defun |
| 910 | |
| 911 | @defun quit-process &optional process current-group |
| 912 | This function sends the signal @code{SIGQUIT} to the process |
| 913 | @var{process}. This signal is the one sent by the ``quit |
| 914 | character'' (usually @kbd{C-b} or @kbd{C-\}) when you are not inside |
| 915 | Emacs. |
| 916 | @end defun |
| 917 | |
| 918 | @defun stop-process &optional process current-group |
| 919 | This function stops the process @var{process} by sending the |
| 920 | signal @code{SIGTSTP}. Use @code{continue-process} to resume its |
| 921 | execution. |
| 922 | |
| 923 | Outside of Emacs, on systems with job control, the ``stop character'' |
| 924 | (usually @kbd{C-z}) normally sends this signal. When |
| 925 | @var{current-group} is non-@code{nil}, you can think of this function as |
| 926 | ``typing @kbd{C-z}'' on the terminal Emacs uses to communicate with the |
| 927 | subprocess. |
| 928 | @end defun |
| 929 | |
| 930 | @defun continue-process &optional process current-group |
| 931 | This function resumes execution of the process @var{process} by sending |
| 932 | it the signal @code{SIGCONT}. This presumes that @var{process} was |
| 933 | stopped previously. |
| 934 | @end defun |
| 935 | |
| 936 | @c Emacs 19 feature |
| 937 | @defun signal-process process signal |
| 938 | This function sends a signal to process @var{process}. The argument |
| 939 | @var{signal} specifies which signal to send; it should be an integer. |
| 940 | |
| 941 | The @var{process} argument can be a system process @acronym{ID}; that |
| 942 | allows you to send signals to processes that are not children of |
| 943 | Emacs. |
| 944 | @end defun |
| 945 | |
| 946 | @node Output from Processes |
| 947 | @section Receiving Output from Processes |
| 948 | @cindex process output |
| 949 | @cindex output from processes |
| 950 | |
| 951 | There are two ways to receive the output that a subprocess writes to |
| 952 | its standard output stream. The output can be inserted in a buffer, |
| 953 | which is called the associated buffer of the process, or a function |
| 954 | called the @dfn{filter function} can be called to act on the output. If |
| 955 | the process has no buffer and no filter function, its output is |
| 956 | discarded. |
| 957 | |
| 958 | When a subprocess terminates, Emacs reads any pending output, |
| 959 | then stops reading output from that subprocess. Therefore, if the |
| 960 | subprocess has children that are still live and still producing |
| 961 | output, Emacs won't receive that output. |
| 962 | |
| 963 | Output from a subprocess can arrive only while Emacs is waiting: when |
| 964 | reading terminal input, in @code{sit-for} and @code{sleep-for} |
| 965 | (@pxref{Waiting}), and in @code{accept-process-output} (@pxref{Accepting |
| 966 | Output}). This minimizes the problem of timing errors that usually |
| 967 | plague parallel programming. For example, you can safely create a |
| 968 | process and only then specify its buffer or filter function; no output |
| 969 | can arrive before you finish, if the code in between does not call any |
| 970 | primitive that waits. |
| 971 | |
| 972 | @defvar process-adaptive-read-buffering |
| 973 | On some systems, when Emacs reads the output from a subprocess, the |
| 974 | output data is read in very small blocks, potentially resulting in |
| 975 | very poor performance. This behaviour can be remedied to some extent |
| 976 | by setting the variable @var{process-adaptive-read-buffering} to a |
| 977 | non-@code{nil} value (the default), as it will automatically delay reading |
| 978 | from such processes, thus allowing them to produce more output before |
| 979 | Emacs tries to read it. |
| 980 | @end defvar |
| 981 | |
| 982 | It is impossible to separate the standard output and standard error |
| 983 | streams of the subprocess, because Emacs normally spawns the subprocess |
| 984 | inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If |
| 985 | you want to keep the output to those streams separate, you should |
| 986 | redirect one of them to a file---for example, by using an appropriate |
| 987 | shell command. |
| 988 | |
| 989 | @menu |
| 990 | * Process Buffers:: If no filter, output is put in a buffer. |
| 991 | * Filter Functions:: Filter functions accept output from the process. |
| 992 | * Decoding Output:: Filters can get unibyte or multibyte strings. |
| 993 | * Accepting Output:: How to wait until process output arrives. |
| 994 | @end menu |
| 995 | |
| 996 | @node Process Buffers |
| 997 | @subsection Process Buffers |
| 998 | |
| 999 | A process can (and usually does) have an @dfn{associated buffer}, |
| 1000 | which is an ordinary Emacs buffer that is used for two purposes: storing |
| 1001 | the output from the process, and deciding when to kill the process. You |
| 1002 | can also use the buffer to identify a process to operate on, since in |
| 1003 | normal practice only one process is associated with any given buffer. |
| 1004 | Many applications of processes also use the buffer for editing input to |
| 1005 | be sent to the process, but this is not built into Emacs Lisp. |
| 1006 | |
| 1007 | Unless the process has a filter function (@pxref{Filter Functions}), |
| 1008 | its output is inserted in the associated buffer. The position to insert |
| 1009 | the output is determined by the @code{process-mark}, which is then |
| 1010 | updated to point to the end of the text just inserted. Usually, but not |
| 1011 | always, the @code{process-mark} is at the end of the buffer. |
| 1012 | |
| 1013 | @defun process-buffer process |
| 1014 | This function returns the associated buffer of the process |
| 1015 | @var{process}. |
| 1016 | |
| 1017 | @smallexample |
| 1018 | @group |
| 1019 | (process-buffer (get-process "shell")) |
| 1020 | @result{} #<buffer *shell*> |
| 1021 | @end group |
| 1022 | @end smallexample |
| 1023 | @end defun |
| 1024 | |
| 1025 | @defun process-mark process |
| 1026 | This function returns the process marker for @var{process}, which is the |
| 1027 | marker that says where to insert output from the process. |
| 1028 | |
| 1029 | If @var{process} does not have a buffer, @code{process-mark} returns a |
| 1030 | marker that points nowhere. |
| 1031 | |
| 1032 | Insertion of process output in a buffer uses this marker to decide where |
| 1033 | to insert, and updates it to point after the inserted text. That is why |
| 1034 | successive batches of output are inserted consecutively. |
| 1035 | |
| 1036 | Filter functions normally should use this marker in the same fashion |
| 1037 | as is done by direct insertion of output in the buffer. A good |
| 1038 | example of a filter function that uses @code{process-mark} is found at |
| 1039 | the end of the following section. |
| 1040 | |
| 1041 | When the user is expected to enter input in the process buffer for |
| 1042 | transmission to the process, the process marker separates the new input |
| 1043 | from previous output. |
| 1044 | @end defun |
| 1045 | |
| 1046 | @defun set-process-buffer process buffer |
| 1047 | This function sets the buffer associated with @var{process} to |
| 1048 | @var{buffer}. If @var{buffer} is @code{nil}, the process becomes |
| 1049 | associated with no buffer. |
| 1050 | @end defun |
| 1051 | |
| 1052 | @defun get-buffer-process buffer-or-name |
| 1053 | This function returns a nondeleted process associated with the buffer |
| 1054 | specified by @var{buffer-or-name}. If there are several processes |
| 1055 | associated with it, this function chooses one (currently, the one most |
| 1056 | recently created, but don't count on that). Deletion of a process |
| 1057 | (see @code{delete-process}) makes it ineligible for this function to |
| 1058 | return. |
| 1059 | |
| 1060 | It is usually a bad idea to have more than one process associated with |
| 1061 | the same buffer. |
| 1062 | |
| 1063 | @smallexample |
| 1064 | @group |
| 1065 | (get-buffer-process "*shell*") |
| 1066 | @result{} #<process shell> |
| 1067 | @end group |
| 1068 | @end smallexample |
| 1069 | |
| 1070 | Killing the process's buffer deletes the process, which kills the |
| 1071 | subprocess with a @code{SIGHUP} signal (@pxref{Signals to Processes}). |
| 1072 | @end defun |
| 1073 | |
| 1074 | @node Filter Functions |
| 1075 | @subsection Process Filter Functions |
| 1076 | @cindex filter function |
| 1077 | @cindex process filter |
| 1078 | |
| 1079 | A process @dfn{filter function} is a function that receives the |
| 1080 | standard output from the associated process. If a process has a filter, |
| 1081 | then @emph{all} output from that process is passed to the filter. The |
| 1082 | process buffer is used directly for output from the process only when |
| 1083 | there is no filter. |
| 1084 | |
| 1085 | The filter function can only be called when Emacs is waiting for |
| 1086 | something, because process output arrives only at such times. Emacs |
| 1087 | waits when reading terminal input, in @code{sit-for} and |
| 1088 | @code{sleep-for} (@pxref{Waiting}), and in @code{accept-process-output} |
| 1089 | (@pxref{Accepting Output}). |
| 1090 | |
| 1091 | A filter function must accept two arguments: the associated process |
| 1092 | and a string, which is output just received from it. The function is |
| 1093 | then free to do whatever it chooses with the output. |
| 1094 | |
| 1095 | Quitting is normally inhibited within a filter function---otherwise, |
| 1096 | the effect of typing @kbd{C-g} at command level or to quit a user |
| 1097 | command would be unpredictable. If you want to permit quitting inside a |
| 1098 | filter function, bind @code{inhibit-quit} to @code{nil}. |
| 1099 | @xref{Quitting}. |
| 1100 | |
| 1101 | If an error happens during execution of a filter function, it is |
| 1102 | caught automatically, so that it doesn't stop the execution of whatever |
| 1103 | program was running when the filter function was started. However, if |
| 1104 | @code{debug-on-error} is non-@code{nil}, the error-catching is turned |
| 1105 | off. This makes it possible to use the Lisp debugger to debug the |
| 1106 | filter function. @xref{Debugger}. |
| 1107 | |
| 1108 | Many filter functions sometimes or always insert the text in the |
| 1109 | process's buffer, mimicking the actions of Emacs when there is no |
| 1110 | filter. Such filter functions need to use @code{set-buffer} in order to |
| 1111 | be sure to insert in that buffer. To avoid setting the current buffer |
| 1112 | semipermanently, these filter functions must save and restore the |
| 1113 | current buffer. They should also update the process marker, and in some |
| 1114 | cases update the value of point. Here is how to do these things: |
| 1115 | |
| 1116 | @smallexample |
| 1117 | @group |
| 1118 | (defun ordinary-insertion-filter (proc string) |
| 1119 | (with-current-buffer (process-buffer proc) |
| 1120 | (let ((moving (= (point) (process-mark proc)))) |
| 1121 | @end group |
| 1122 | @group |
| 1123 | (save-excursion |
| 1124 | ;; @r{Insert the text, advancing the process marker.} |
| 1125 | (goto-char (process-mark proc)) |
| 1126 | (insert string) |
| 1127 | (set-marker (process-mark proc) (point))) |
| 1128 | (if moving (goto-char (process-mark proc)))))) |
| 1129 | @end group |
| 1130 | @end smallexample |
| 1131 | |
| 1132 | @noindent |
| 1133 | The reason to use @code{with-current-buffer}, rather than using |
| 1134 | @code{save-excursion} to save and restore the current buffer, is so as |
| 1135 | to preserve the change in point made by the second call to |
| 1136 | @code{goto-char}. |
| 1137 | |
| 1138 | To make the filter force the process buffer to be visible whenever new |
| 1139 | text arrives, insert the following line just before the |
| 1140 | @code{with-current-buffer} construct: |
| 1141 | |
| 1142 | @smallexample |
| 1143 | (display-buffer (process-buffer proc)) |
| 1144 | @end smallexample |
| 1145 | |
| 1146 | To force point to the end of the new output, no matter where it was |
| 1147 | previously, eliminate the variable @code{moving} and call |
| 1148 | @code{goto-char} unconditionally. |
| 1149 | |
| 1150 | In earlier Emacs versions, every filter function that did regular |
| 1151 | expression searching or matching had to explicitly save and restore the |
| 1152 | match data. Now Emacs does this automatically for filter functions; |
| 1153 | they never need to do it explicitly. @xref{Match Data}. |
| 1154 | |
| 1155 | A filter function that writes the output into the buffer of the |
| 1156 | process should check whether the buffer is still alive. If it tries to |
| 1157 | insert into a dead buffer, it will get an error. The expression |
| 1158 | @code{(buffer-name (process-buffer @var{process}))} returns @code{nil} |
| 1159 | if the buffer is dead. |
| 1160 | |
| 1161 | The output to the function may come in chunks of any size. A program |
| 1162 | that produces the same output twice in a row may send it as one batch of |
| 1163 | 200 characters one time, and five batches of 40 characters the next. If |
| 1164 | the filter looks for certain text strings in the subprocess output, make |
| 1165 | sure to handle the case where one of these strings is split across two |
| 1166 | or more batches of output. |
| 1167 | |
| 1168 | @defun set-process-filter process filter |
| 1169 | This function gives @var{process} the filter function @var{filter}. If |
| 1170 | @var{filter} is @code{nil}, it gives the process no filter. |
| 1171 | @end defun |
| 1172 | |
| 1173 | @defun process-filter process |
| 1174 | This function returns the filter function of @var{process}, or @code{nil} |
| 1175 | if it has none. |
| 1176 | @end defun |
| 1177 | |
| 1178 | Here is an example of use of a filter function: |
| 1179 | |
| 1180 | @smallexample |
| 1181 | @group |
| 1182 | (defun keep-output (process output) |
| 1183 | (setq kept (cons output kept))) |
| 1184 | @result{} keep-output |
| 1185 | @end group |
| 1186 | @group |
| 1187 | (setq kept nil) |
| 1188 | @result{} nil |
| 1189 | @end group |
| 1190 | @group |
| 1191 | (set-process-filter (get-process "shell") 'keep-output) |
| 1192 | @result{} keep-output |
| 1193 | @end group |
| 1194 | @group |
| 1195 | (process-send-string "shell" "ls ~/other\n") |
| 1196 | @result{} nil |
| 1197 | kept |
| 1198 | @result{} ("lewis@@slug[8] % " |
| 1199 | @end group |
| 1200 | @group |
| 1201 | "FINAL-W87-SHORT.MSS backup.otl kolstad.mss~ |
| 1202 | address.txt backup.psf kolstad.psf |
| 1203 | backup.bib~ david.mss resume-Dec-86.mss~ |
| 1204 | backup.err david.psf resume-Dec.psf |
| 1205 | backup.mss dland syllabus.mss |
| 1206 | " |
| 1207 | "#backups.mss# backup.mss~ kolstad.mss |
| 1208 | ") |
| 1209 | @end group |
| 1210 | @end smallexample |
| 1211 | |
| 1212 | @ignore @c The code in this example doesn't show the right way to do things. |
| 1213 | Here is another, more realistic example, which demonstrates how to use |
| 1214 | the process mark to do insertion in the same fashion as is done when |
| 1215 | there is no filter function: |
| 1216 | |
| 1217 | @smallexample |
| 1218 | @group |
| 1219 | ;; @r{Insert input in the buffer specified by @code{my-shell-buffer}} |
| 1220 | ;; @r{and make sure that buffer is shown in some window.} |
| 1221 | (defun my-process-filter (proc str) |
| 1222 | (let ((cur (selected-window)) |
| 1223 | (pop-up-windows t)) |
| 1224 | (pop-to-buffer my-shell-buffer) |
| 1225 | @end group |
| 1226 | @group |
| 1227 | (goto-char (point-max)) |
| 1228 | (insert str) |
| 1229 | (set-marker (process-mark proc) (point-max)) |
| 1230 | (select-window cur))) |
| 1231 | @end group |
| 1232 | @end smallexample |
| 1233 | @end ignore |
| 1234 | |
| 1235 | @node Decoding Output |
| 1236 | @subsection Decoding Process Output |
| 1237 | |
| 1238 | When Emacs writes process output directly into a multibyte buffer, |
| 1239 | it decodes the output according to the process output coding system. |
| 1240 | If the coding system is @code{raw-text} or @code{no-conversion}, Emacs |
| 1241 | converts the unibyte output to multibyte using |
| 1242 | @code{string-to-multibyte}, and inserts the resulting multibyte text. |
| 1243 | |
| 1244 | You can use @code{set-process-coding-system} to specify which coding |
| 1245 | system to use (@pxref{Process Information}). Otherwise, the coding |
| 1246 | system comes from @code{coding-system-for-read}, if that is |
| 1247 | non-@code{nil}; or else from the defaulting mechanism (@pxref{Default |
| 1248 | Coding Systems}). |
| 1249 | |
| 1250 | @strong{Warning:} Coding systems such as @code{undecided} which |
| 1251 | determine the coding system from the data do not work entirely |
| 1252 | reliably with asynchronous subprocess output. This is because Emacs |
| 1253 | has to process asynchronous subprocess output in batches, as it |
| 1254 | arrives. Emacs must try to detect the proper coding system from one |
| 1255 | batch at a time, and this does not always work. Therefore, if at all |
| 1256 | possible, specify a coding system that determines both the character |
| 1257 | code conversion and the end of line conversion---that is, one like |
| 1258 | @code{latin-1-unix}, rather than @code{undecided} or @code{latin-1}. |
| 1259 | |
| 1260 | @cindex filter multibyte flag, of process |
| 1261 | @cindex process filter multibyte flag |
| 1262 | When Emacs calls a process filter function, it provides the process |
| 1263 | output as a multibyte string or as a unibyte string according to the |
| 1264 | process's filter multibyte flag. If the flag is non-@code{nil}, Emacs |
| 1265 | decodes the output according to the process output coding system to |
| 1266 | produce a multibyte string, and passes that to the process. If the |
| 1267 | flag is @code{nil}, Emacs puts the output into a unibyte string, with |
| 1268 | no decoding, and passes that. |
| 1269 | |
| 1270 | When you create a process, the filter multibyte flag takes its |
| 1271 | initial value from @code{default-enable-multibyte-characters}. If you |
| 1272 | want to change the flag later on, use |
| 1273 | @code{set-process-filter-multibyte}. |
| 1274 | |
| 1275 | @defun set-process-filter-multibyte process multibyte |
| 1276 | This function sets the filter multibyte flag of @var{process} |
| 1277 | to @var{multibyte}. |
| 1278 | @end defun |
| 1279 | |
| 1280 | @defun process-filter-multibyte-p process |
| 1281 | This function returns the filter multibyte flag of @var{process}. |
| 1282 | @end defun |
| 1283 | |
| 1284 | @node Accepting Output |
| 1285 | @subsection Accepting Output from Processes |
| 1286 | |
| 1287 | Output from asynchronous subprocesses normally arrives only while |
| 1288 | Emacs is waiting for some sort of external event, such as elapsed time |
| 1289 | or terminal input. Occasionally it is useful in a Lisp program to |
| 1290 | explicitly permit output to arrive at a specific point, or even to wait |
| 1291 | until output arrives from a process. |
| 1292 | |
| 1293 | @defun accept-process-output &optional process seconds millisec just-this-one |
| 1294 | This function allows Emacs to read pending output from processes. The |
| 1295 | output is inserted in the associated buffers or given to their filter |
| 1296 | functions. If @var{process} is non-@code{nil} then this function does |
| 1297 | not return until some output has been received from @var{process}. |
| 1298 | |
| 1299 | @c Emacs 19 feature |
| 1300 | The arguments @var{seconds} and @var{millisec} let you specify timeout |
| 1301 | periods. The former specifies a period measured in seconds and the |
| 1302 | latter specifies one measured in milliseconds. The two time periods |
| 1303 | thus specified are added together, and @code{accept-process-output} |
| 1304 | returns after that much time whether or not there has been any |
| 1305 | subprocess output. |
| 1306 | |
| 1307 | The argument @var{seconds} need not be an integer. If it is a floating |
| 1308 | point number, this function waits for a fractional number of seconds. |
| 1309 | Some systems support only a whole number of seconds; on these systems, |
| 1310 | @var{seconds} is rounded down. |
| 1311 | |
| 1312 | Not all operating systems support waiting periods other than multiples |
| 1313 | of a second; on those that do not, you get an error if you specify |
| 1314 | nonzero @var{millisec}. |
| 1315 | |
| 1316 | @c Emacs 22.1 feature |
| 1317 | If @var{process} is a process, and the argument @var{just-this-one} is |
| 1318 | non-@code{nil}, only output from that process is handled, suspending output |
| 1319 | from other processes until some output has been received from that |
| 1320 | process or the timeout expires. If @var{just-this-one} is an integer, |
| 1321 | also inhibit running timers. This feature is generally not |
| 1322 | recommended, but may be necessary for specific applications, such as |
| 1323 | speech synthesis. |
| 1324 | |
| 1325 | The function @code{accept-process-output} returns non-@code{nil} if it |
| 1326 | did get some output, or @code{nil} if the timeout expired before output |
| 1327 | arrived. |
| 1328 | @end defun |
| 1329 | |
| 1330 | @node Sentinels |
| 1331 | @section Sentinels: Detecting Process Status Changes |
| 1332 | @cindex process sentinel |
| 1333 | @cindex sentinel |
| 1334 | |
| 1335 | A @dfn{process sentinel} is a function that is called whenever the |
| 1336 | associated process changes status for any reason, including signals |
| 1337 | (whether sent by Emacs or caused by the process's own actions) that |
| 1338 | terminate, stop, or continue the process. The process sentinel is |
| 1339 | also called if the process exits. The sentinel receives two |
| 1340 | arguments: the process for which the event occurred, and a string |
| 1341 | describing the type of event. |
| 1342 | |
| 1343 | The string describing the event looks like one of the following: |
| 1344 | |
| 1345 | @itemize @bullet |
| 1346 | @item |
| 1347 | @code{"finished\n"}. |
| 1348 | |
| 1349 | @item |
| 1350 | @code{"exited abnormally with code @var{exitcode}\n"}. |
| 1351 | |
| 1352 | @item |
| 1353 | @code{"@var{name-of-signal}\n"}. |
| 1354 | |
| 1355 | @item |
| 1356 | @code{"@var{name-of-signal} (core dumped)\n"}. |
| 1357 | @end itemize |
| 1358 | |
| 1359 | A sentinel runs only while Emacs is waiting (e.g., for terminal |
| 1360 | input, or for time to elapse, or for process output). This avoids the |
| 1361 | timing errors that could result from running them at random places in |
| 1362 | the middle of other Lisp programs. A program can wait, so that |
| 1363 | sentinels will run, by calling @code{sit-for} or @code{sleep-for} |
| 1364 | (@pxref{Waiting}), or @code{accept-process-output} (@pxref{Accepting |
| 1365 | Output}). Emacs also allows sentinels to run when the command loop is |
| 1366 | reading input. @code{delete-process} calls the sentinel when it |
| 1367 | terminates a running process. |
| 1368 | |
| 1369 | Emacs does not keep a queue of multiple reasons to call the sentinel |
| 1370 | of one process; it records just the current status and the fact that |
| 1371 | there has been a change. Therefore two changes in status, coming in |
| 1372 | quick succession, can call the sentinel just once. However, process |
| 1373 | termination will always run the sentinel exactly once. This is |
| 1374 | because the process status can't change again after termination. |
| 1375 | |
| 1376 | Quitting is normally inhibited within a sentinel---otherwise, the |
| 1377 | effect of typing @kbd{C-g} at command level or to quit a user command |
| 1378 | would be unpredictable. If you want to permit quitting inside a |
| 1379 | sentinel, bind @code{inhibit-quit} to @code{nil}. @xref{Quitting}. |
| 1380 | |
| 1381 | A sentinel that writes the output into the buffer of the process |
| 1382 | should check whether the buffer is still alive. If it tries to insert |
| 1383 | into a dead buffer, it will get an error. If the buffer is dead, |
| 1384 | @code{(buffer-name (process-buffer @var{process}))} returns @code{nil}. |
| 1385 | |
| 1386 | If an error happens during execution of a sentinel, it is caught |
| 1387 | automatically, so that it doesn't stop the execution of whatever |
| 1388 | programs was running when the sentinel was started. However, if |
| 1389 | @code{debug-on-error} is non-@code{nil}, the error-catching is turned |
| 1390 | off. This makes it possible to use the Lisp debugger to debug the |
| 1391 | sentinel. @xref{Debugger}. |
| 1392 | |
| 1393 | While a sentinel is running, the process sentinel is temporarily |
| 1394 | set to @code{nil} so that the sentinel won't run recursively. |
| 1395 | For this reason it is not possible for a sentinel to specify |
| 1396 | a new sentinel. |
| 1397 | |
| 1398 | In earlier Emacs versions, every sentinel that did regular expression |
| 1399 | searching or matching had to explicitly save and restore the match data. |
| 1400 | Now Emacs does this automatically for sentinels; they never need to do |
| 1401 | it explicitly. @xref{Match Data}. |
| 1402 | |
| 1403 | @defun set-process-sentinel process sentinel |
| 1404 | This function associates @var{sentinel} with @var{process}. If |
| 1405 | @var{sentinel} is @code{nil}, then the process will have no sentinel. |
| 1406 | The default behavior when there is no sentinel is to insert a message in |
| 1407 | the process's buffer when the process status changes. |
| 1408 | |
| 1409 | Changes in process sentinel take effect immediately---if the sentinel |
| 1410 | is slated to be run but has not been called yet, and you specify a new |
| 1411 | sentinel, the eventual call to the sentinel will use the new one. |
| 1412 | |
| 1413 | @smallexample |
| 1414 | @group |
| 1415 | (defun msg-me (process event) |
| 1416 | (princ |
| 1417 | (format "Process: %s had the event `%s'" process event))) |
| 1418 | (set-process-sentinel (get-process "shell") 'msg-me) |
| 1419 | @result{} msg-me |
| 1420 | @end group |
| 1421 | @group |
| 1422 | (kill-process (get-process "shell")) |
| 1423 | @print{} Process: #<process shell> had the event `killed' |
| 1424 | @result{} #<process shell> |
| 1425 | @end group |
| 1426 | @end smallexample |
| 1427 | @end defun |
| 1428 | |
| 1429 | @defun process-sentinel process |
| 1430 | This function returns the sentinel of @var{process}, or @code{nil} if it |
| 1431 | has none. |
| 1432 | @end defun |
| 1433 | |
| 1434 | @defun waiting-for-user-input-p |
| 1435 | While a sentinel or filter function is running, this function returns |
| 1436 | non-@code{nil} if Emacs was waiting for keyboard input from the user at |
| 1437 | the time the sentinel or filter function was called, @code{nil} if it |
| 1438 | was not. |
| 1439 | @end defun |
| 1440 | |
| 1441 | @node Query Before Exit |
| 1442 | @section Querying Before Exit |
| 1443 | |
| 1444 | When Emacs exits, it terminates all its subprocesses by sending them |
| 1445 | the @code{SIGHUP} signal. Because subprocesses may be doing |
| 1446 | valuable work, Emacs normally asks the user to confirm that it is ok |
| 1447 | to terminate them. Each process has a query flag which, if |
| 1448 | non-@code{nil}, says that Emacs should ask for confirmation before |
| 1449 | exiting and thus killing that process. The default for the query flag |
| 1450 | is @code{t}, meaning @emph{do} query. |
| 1451 | |
| 1452 | @tindex process-query-on-exit-flag |
| 1453 | @defun process-query-on-exit-flag process |
| 1454 | This returns the query flag of @var{process}. |
| 1455 | @end defun |
| 1456 | |
| 1457 | @tindex set-process-query-on-exit-flag |
| 1458 | @defun set-process-query-on-exit-flag process flag |
| 1459 | This function sets the query flag of @var{process} to @var{flag}. It |
| 1460 | returns @var{flag}. |
| 1461 | |
| 1462 | @smallexample |
| 1463 | @group |
| 1464 | ;; @r{Don't query about the shell process} |
| 1465 | (set-process-query-on-exit-flag (get-process "shell") nil) |
| 1466 | @result{} t |
| 1467 | @end group |
| 1468 | @end smallexample |
| 1469 | @end defun |
| 1470 | |
| 1471 | @defun process-kill-without-query process &optional do-query |
| 1472 | This function clears the query flag of @var{process}, so that |
| 1473 | Emacs will not query the user on account of that process. |
| 1474 | |
| 1475 | Actually, the function does more than that: it returns the old value of |
| 1476 | the process's query flag, and sets the query flag to @var{do-query}. |
| 1477 | Please don't use this function to do those things any more---please |
| 1478 | use the newer, cleaner functions @code{process-query-on-exit-flag} and |
| 1479 | @code{set-process-query-on-exit-flag} in all but the simplest cases. |
| 1480 | The only way you should use @code{process-kill-without-query} nowadays |
| 1481 | is like this: |
| 1482 | |
| 1483 | @smallexample |
| 1484 | @group |
| 1485 | ;; @r{Don't query about the shell process} |
| 1486 | (process-kill-without-query (get-process "shell")) |
| 1487 | @end group |
| 1488 | @end smallexample |
| 1489 | @end defun |
| 1490 | |
| 1491 | @node Transaction Queues |
| 1492 | @section Transaction Queues |
| 1493 | @cindex transaction queue |
| 1494 | |
| 1495 | You can use a @dfn{transaction queue} to communicate with a subprocess |
| 1496 | using transactions. First use @code{tq-create} to create a transaction |
| 1497 | queue communicating with a specified process. Then you can call |
| 1498 | @code{tq-enqueue} to send a transaction. |
| 1499 | |
| 1500 | @defun tq-create process |
| 1501 | This function creates and returns a transaction queue communicating with |
| 1502 | @var{process}. The argument @var{process} should be a subprocess |
| 1503 | capable of sending and receiving streams of bytes. It may be a child |
| 1504 | process, or it may be a TCP connection to a server, possibly on another |
| 1505 | machine. |
| 1506 | @end defun |
| 1507 | |
| 1508 | @defun tq-enqueue queue question regexp closure fn |
| 1509 | This function sends a transaction to queue @var{queue}. Specifying the |
| 1510 | queue has the effect of specifying the subprocess to talk to. |
| 1511 | |
| 1512 | The argument @var{question} is the outgoing message that starts the |
| 1513 | transaction. The argument @var{fn} is the function to call when the |
| 1514 | corresponding answer comes back; it is called with two arguments: |
| 1515 | @var{closure}, and the answer received. |
| 1516 | |
| 1517 | The argument @var{regexp} is a regular expression that should match |
| 1518 | text at the end of the entire answer, but nothing before; that's how |
| 1519 | @code{tq-enqueue} determines where the answer ends. |
| 1520 | |
| 1521 | The return value of @code{tq-enqueue} itself is not meaningful. |
| 1522 | @end defun |
| 1523 | |
| 1524 | @defun tq-close queue |
| 1525 | Shut down transaction queue @var{queue}, waiting for all pending transactions |
| 1526 | to complete, and then terminate the connection or child process. |
| 1527 | @end defun |
| 1528 | |
| 1529 | Transaction queues are implemented by means of a filter function. |
| 1530 | @xref{Filter Functions}. |
| 1531 | |
| 1532 | @node Network |
| 1533 | @section Network Connections |
| 1534 | @cindex network connection |
| 1535 | @cindex TCP |
| 1536 | @cindex UDP |
| 1537 | |
| 1538 | Emacs Lisp programs can open stream (TCP) and datagram (UDP) network |
| 1539 | connections to other processes on the same machine or other machines. |
| 1540 | A network connection is handled by Lisp much like a subprocess, and is |
| 1541 | represented by a process object. However, the process you are |
| 1542 | communicating with is not a child of the Emacs process, so it has no |
| 1543 | process @acronym{ID}, and you can't kill it or send it signals. All you |
| 1544 | can do is send and receive data. @code{delete-process} closes the |
| 1545 | connection, but does not kill the program at the other end; that |
| 1546 | program must decide what to do about closure of the connection. |
| 1547 | |
| 1548 | Lisp programs can listen for connections by creating network |
| 1549 | servers. A network server is also represented by a kind of process |
| 1550 | object, but unlike a network connection, the network server never |
| 1551 | transfers data itself. When it receives a connection request, it |
| 1552 | creates a new network connection to represent the connection just |
| 1553 | made. (The network connection inherits certain information, including |
| 1554 | the process plist, from the server.) The network server then goes |
| 1555 | back to listening for more connection requests. |
| 1556 | |
| 1557 | Network connections and servers are created by calling |
| 1558 | @code{make-network-process} with an argument list consisting of |
| 1559 | keyword/argument pairs, for example @code{:server t} to create a |
| 1560 | server process, or @code{:type 'datagram} to create a datagram |
| 1561 | connection. @xref{Low-Level Network}, for details. You can also use |
| 1562 | one of the @code{open-network-...} functions descibed below; |
| 1563 | internally, they just call @code{make-network-process} with suitable |
| 1564 | arguments. |
| 1565 | |
| 1566 | You can distinguish process objects representing network connections |
| 1567 | and servers from those representing subprocesses with the |
| 1568 | @code{process-status} function. The possible status values for |
| 1569 | network connections are @code{open}, @code{closed}, @code{connect}, |
| 1570 | and @code{failed}. For a network server, the status is always |
| 1571 | @code{listen}. None of those values is possible for a real |
| 1572 | subprocess. @xref{Process Information}. |
| 1573 | |
| 1574 | You can stop and resume operation of a network process by calling |
| 1575 | @code{stop-process} and @code{continue-process}. For a server |
| 1576 | process, being stopped means not accepting new connections. (Up to 5 |
| 1577 | connection requests will be queued for when you resume the server; you |
| 1578 | can increase this limit, unless it is imposed by the operating |
| 1579 | systems.) For a network stream connection, being stopped means not |
| 1580 | processing input (any arriving input waits until you resume the |
| 1581 | connection). For a datagram connection, some number of packets may be |
| 1582 | queued but input may be lost. You can use the function |
| 1583 | @code{process-command} to determine whether a network connection or |
| 1584 | server is stopped; a non-@code{nil} value means yes. |
| 1585 | |
| 1586 | @defun open-network-stream name buffer-or-name host service |
| 1587 | This function opens a TCP connection, and returns a process object |
| 1588 | that represents the connection. |
| 1589 | |
| 1590 | The @var{name} argument specifies the name for the process object. It |
| 1591 | is modified as necessary to make it unique. |
| 1592 | |
| 1593 | The @var{buffer-or-name} argument is the buffer to associate with the |
| 1594 | connection. Output from the connection is inserted in the buffer, |
| 1595 | unless you specify a filter function to handle the output. If |
| 1596 | @var{buffer-or-name} is @code{nil}, it means that the connection is not |
| 1597 | associated with any buffer. |
| 1598 | |
| 1599 | The arguments @var{host} and @var{service} specify where to connect to; |
| 1600 | @var{host} is the host name (a string), and @var{service} is the name of |
| 1601 | a defined network service (a string) or a port number (an integer). |
| 1602 | @end defun |
| 1603 | |
| 1604 | @defun open-network-stream-nowait name buffer-or-name host service &optional sentinel filter |
| 1605 | This function opens a TCP connection, like @code{open-network-stream}, |
| 1606 | but it returns immediately without waiting for the request to be |
| 1607 | accepted or rejected by the remote server. When the request is |
| 1608 | subsequently accepted or rejected, the process's sentinel function |
| 1609 | will be called with a string that starts with @code{"open"} (on |
| 1610 | success) or @code{"failed"} (on error). |
| 1611 | |
| 1612 | Some systems do not support non-blocking connections; on those |
| 1613 | systems, @code{open-network-stream-nowait} returns @code{nil} |
| 1614 | and does nothing. |
| 1615 | |
| 1616 | The optional arguments @var{sentinel} and @var{filter} specify the |
| 1617 | sentinel and filter functions for this network connection. It is |
| 1618 | useful to specify them when opening the connection, because they will |
| 1619 | be used later asynchronously. The other arguments mean the same as in |
| 1620 | @code{open-network-stream}. |
| 1621 | @end defun |
| 1622 | |
| 1623 | @defun process-contact process &optional key |
| 1624 | This function returns information about how a network process was set |
| 1625 | up. For a connection, when @var{key} is @code{nil}, it returns |
| 1626 | @code{(@var{hostname} @var{service})} which specifies what you |
| 1627 | connected to. |
| 1628 | |
| 1629 | If @var{key} is @code{t}, the value is the complete status information |
| 1630 | for the connection or server; that is, the list of keywords and values |
| 1631 | specified in @code{make-network-process}, except that some of the |
| 1632 | values represent the current status instead of what you specified: |
| 1633 | |
| 1634 | @table @code |
| 1635 | @item :buffer |
| 1636 | The associated value is the process buffer. |
| 1637 | @item :filter |
| 1638 | The associated value is the process filter function. |
| 1639 | @item :sentinel |
| 1640 | The associated value is the process sentinel function. |
| 1641 | @item :remote |
| 1642 | In a connection, this is the address in internal format of the remote peer. |
| 1643 | @item :local |
| 1644 | The local address, in internal format. |
| 1645 | @item :service |
| 1646 | In a server, if you specified @code{t} for @var{service}, |
| 1647 | this value is the actual port number. |
| 1648 | @end table |
| 1649 | |
| 1650 | @code{:local} and @code{:remote} are included even if they were not |
| 1651 | specified explicitly in @code{make-network-process}. |
| 1652 | |
| 1653 | If @var{key} is a keyword, the function returns the value corresponding |
| 1654 | to that keyword. |
| 1655 | |
| 1656 | For an ordinary child process, this function always returns @code{t}. |
| 1657 | @end defun |
| 1658 | |
| 1659 | @node Network Servers |
| 1660 | @section Network Servers |
| 1661 | |
| 1662 | You create a server by calling @code{make-network-process} with |
| 1663 | @code{:server t}. The server will listen for connection requests from |
| 1664 | clients. When it accepts a client connection request, that creates a |
| 1665 | new network connection, itself a process object, with the following |
| 1666 | parameters: |
| 1667 | |
| 1668 | @itemize @bullet |
| 1669 | @item |
| 1670 | The connection's process name is constructed by concatenating the |
| 1671 | server process' @var{name} with a client identification string. The |
| 1672 | client identification string for an IPv4 connection looks like |
| 1673 | @samp{<@var{a}.@var{b}.@var{c}.@var{d}:@var{p}>}. Otherwise, it is a |
| 1674 | unique number in brackets, as in @samp{<@var{nnn}>}. The number |
| 1675 | is unique for each connection in the Emacs session. |
| 1676 | |
| 1677 | @item |
| 1678 | If the server's filter is non-@code{nil}, the connection process does |
| 1679 | not get a separate process buffer; otherwise, Emacs creates a new |
| 1680 | buffer for the purpose. The buffer name is the server's buffer name |
| 1681 | or process name, concatenated with the client identification string. |
| 1682 | |
| 1683 | The server's process buffer value is never used directly by Emacs, but |
| 1684 | it is passed to the log function, which can log connections by |
| 1685 | inserting text there. |
| 1686 | |
| 1687 | @item |
| 1688 | The communication type and the process filter and sentinel are |
| 1689 | inherited from those of the server. The server never directly |
| 1690 | uses its filter and sentinel; their sole purpose is to initialize |
| 1691 | connections made to the server. |
| 1692 | |
| 1693 | @item |
| 1694 | The connection's process contact info is set according to the client's |
| 1695 | addressing information (typically an IP address and a port number). |
| 1696 | This information is associated with the @code{process-contact} |
| 1697 | keywords @code{:host}, @code{:service}, @code{:remote}. |
| 1698 | |
| 1699 | @item |
| 1700 | The connection's local address is set up according to the port |
| 1701 | number used for the connection. |
| 1702 | |
| 1703 | @item |
| 1704 | The client process' plist is initialized from the server's plist. |
| 1705 | @end itemize |
| 1706 | |
| 1707 | @defun open-network-stream-server name buffer-or-name service &optional sentinel filter |
| 1708 | Create a network server process for a TCP service. |
| 1709 | It returns @code{nil} if server processes are not supported; otherwise, |
| 1710 | it returns a subprocess-object to represent the server. |
| 1711 | |
| 1712 | When a client connects to the specified service, Emacs creates a new |
| 1713 | subprocess to handle the new connection, and then calls its sentinel |
| 1714 | function (which it has inherited from the server). |
| 1715 | |
| 1716 | The optional arguments @var{sentinel} and @var{filter} specify the |
| 1717 | sentinel and filter functions for the server. It is useful to specify |
| 1718 | them now, because they will be used later asynchronously when the |
| 1719 | server receives a connection request. The three arguments @var{name}, |
| 1720 | @var{buffer-or-name} and @var{service} mean the same thing as in |
| 1721 | @code{open-network-stream}, but @var{service} can be @code{t} |
| 1722 | meaning ask the system to allocate an unused port to listen on. |
| 1723 | @end defun |
| 1724 | |
| 1725 | @node Datagrams |
| 1726 | @section Datagrams |
| 1727 | @cindex datagrams |
| 1728 | |
| 1729 | A datagram connection communicates with individual packets rather |
| 1730 | than streams of data. Each call to @code{process-send} sends one |
| 1731 | datagram packet (@pxref{Input to Processes}), and each datagram |
| 1732 | received results in one call to the filter function. |
| 1733 | |
| 1734 | The datagram connection doesn't have to talk with the same remote |
| 1735 | peer all the time. It has a @dfn{remote peer address} which specifies |
| 1736 | where to send datagrams to. Each time an incoming datagram is passed |
| 1737 | to the filter function, the peer address is set to the address that |
| 1738 | datagram came from; that way, if the filter function sends a datagram, |
| 1739 | it will go back to that place. You can specify the remote peer |
| 1740 | address when you create the datagram connection using the |
| 1741 | @code{:remote} keyword. You can change it later on by calling |
| 1742 | @code{set-process-datagram-address}. |
| 1743 | |
| 1744 | @defun process-datagram-address process |
| 1745 | If @var{process} is a datagram connection or server, this function |
| 1746 | returns its remote peer address. |
| 1747 | @end defun |
| 1748 | |
| 1749 | @defun set-process-datagram-address process address |
| 1750 | If @var{process} is a datagram connection or server, this function |
| 1751 | sets its remote peer address to @var{address}. |
| 1752 | @end defun |
| 1753 | |
| 1754 | @node Low-Level Network |
| 1755 | @section Low-Level Network Access |
| 1756 | |
| 1757 | The basic function for creating network connections and network |
| 1758 | servers is @code{make-network-process}. It can do either of those |
| 1759 | jobs, depending on the arguments you give it. |
| 1760 | |
| 1761 | @defun make-network-process &rest args |
| 1762 | This function creates a network connection or server and returns the |
| 1763 | process object that represents it. The arguments @var{args} are a |
| 1764 | list of keyword/argument pairs. Omitting a keyword is always |
| 1765 | equivalent to specifying it with value @code{nil}, except for |
| 1766 | @code{:coding}, @code{:filter-multibyte}, and @code{:reuseaddr}. Here |
| 1767 | are the meaningful keywords: |
| 1768 | |
| 1769 | @table @asis |
| 1770 | @item :name name |
| 1771 | Use the string @var{name} as the process name. It is modified if |
| 1772 | necessary to make it unique. |
| 1773 | |
| 1774 | @item :type @var{type} |
| 1775 | Specify the communication type. A value of @code{nil} specifies a |
| 1776 | stream connection (the default); @code{datagram} specifies a datagram |
| 1777 | connection. Both connections and servers can be of either type. |
| 1778 | |
| 1779 | @item :server @var{server-flag} |
| 1780 | If @var{server-flag} is non-@code{nil}, create a server. Otherwise, |
| 1781 | create a connection. For a stream type server, @var{server-flag} may |
| 1782 | be an integer which then specifies the length of the queue of pending |
| 1783 | connections to the server. The default queue length is 5. |
| 1784 | |
| 1785 | @item :host @var{host} |
| 1786 | Specify the host to connect to. @var{host} should be a host name or |
| 1787 | internet address, as a string, or the symbol @code{local} to specify |
| 1788 | the local host. If you specify @var{host} for a server, it must |
| 1789 | specify a valid address for the local host, and only clients |
| 1790 | connecting to that address will be accepted. |
| 1791 | |
| 1792 | @item :service @var{service} |
| 1793 | @var{service} specifies a port number to connect to, or, for a server, |
| 1794 | the port number to listen on. It should be a service name that |
| 1795 | translates to a port number, or an integer specifying the port number |
| 1796 | directly. For a server, it can also be @code{t}, which means to let |
| 1797 | the system select an unused port number. |
| 1798 | |
| 1799 | @item :family @var{family} |
| 1800 | @var{family} specifies the address (and protocol) family for |
| 1801 | communication. @code{nil} stands for IPv4. @code{local} specifies a |
| 1802 | Unix socket, in which case @var{host} is ignored. |
| 1803 | |
| 1804 | @item :local @var{local-address} |
| 1805 | For a server process, @var{local-address} is the address to listen on. |
| 1806 | It overrides @var{family}, @var{host} and @var{service}, and you |
| 1807 | may as well not specify them. |
| 1808 | |
| 1809 | @item :remote @var{remote-address} |
| 1810 | For a connection, @var{remote-address} is the address to connect to. |
| 1811 | It overrides @var{family}, @var{host} and @var{service}, and you |
| 1812 | may as well not specify them. |
| 1813 | |
| 1814 | For a datagram server, @var{remote-address} specifies the initial |
| 1815 | setting of the remote datagram address. |
| 1816 | |
| 1817 | The format of @var{local-address} or @var{remote-address} depends on |
| 1818 | the address family: |
| 1819 | |
| 1820 | @itemize - |
| 1821 | @item |
| 1822 | An IPv4 address is represented as a vector of integers @code{[@var{a} |
| 1823 | @var{b} @var{c} @var{d} @var{p}]} corresponding to numeric IP address |
| 1824 | @var{a}.@var{b}.@var{c}.@var{d} and port number @var{p}. |
| 1825 | |
| 1826 | @item |
| 1827 | A local address is represented as a string which specifies the address |
| 1828 | in the local address space. |
| 1829 | |
| 1830 | @item |
| 1831 | An ``unsupported family'' address is represented by a cons |
| 1832 | @code{(@var{f} . @var{av})}, where @var{f} is the family number and |
| 1833 | @var{av} is a vector specifying the socket address using one element |
| 1834 | per address data byte. Do not rely on this format in portable code, |
| 1835 | as it may depend on implementation defined constants, data sizes, and |
| 1836 | data structure alignment. |
| 1837 | @end itemize |
| 1838 | |
| 1839 | @item :nowait @var{bool} |
| 1840 | If @var{bool} is non-@code{nil} for a stream connection, return |
| 1841 | without waiting for the connection to complete. When the connection |
| 1842 | succeeds or fails, Emacs will call the sentinel function, with a |
| 1843 | second argument matching @code{"open"} (if successful) or |
| 1844 | @code{"failed"}. The default is to block, so that |
| 1845 | @code{make-network-process} does not return until the connection |
| 1846 | has succeeded or failed. |
| 1847 | |
| 1848 | @item :stop @var{stopped} |
| 1849 | Start the network connection or server in the `stopped' state if |
| 1850 | @var{stopped} is non-@code{nil}. |
| 1851 | |
| 1852 | @item :buffer @var{buffer} |
| 1853 | Use @var{buffer} as the process buffer. |
| 1854 | |
| 1855 | @item :coding @var{coding} |
| 1856 | Use @var{coding} as the coding system for this process. To specify |
| 1857 | different coding systems for decoding data from the connection and for |
| 1858 | encoding data sent to it, specify @code{(@var{decoding} . |
| 1859 | @var{encoding})} for @var{coding}. |
| 1860 | |
| 1861 | If you don't specify this keyword at all, the default |
| 1862 | is to determine the coding systems from the data. |
| 1863 | |
| 1864 | @item :noquery @var{query-flag} |
| 1865 | Initialize the process query flag to @var{query-flag}. @xref{Query Before Exit}. |
| 1866 | |
| 1867 | @item :filter @var{filter} |
| 1868 | Initialize the process filter to @var{filter}. |
| 1869 | |
| 1870 | @item :filter-multibyte @var{bool} |
| 1871 | If @var{bool} is non-@code{nil}, strings given to the process filter |
| 1872 | are multibyte, otherwise they are unibyte. If you don't specify this |
| 1873 | keyword at all, the default is that the strings are multibyte if |
| 1874 | @code{default-enable-multibyte-characters} is non-@code{nil}. |
| 1875 | |
| 1876 | @item :sentinel @var{sentinel} |
| 1877 | Initialize the process sentinel to @var{sentinel}. |
| 1878 | |
| 1879 | @item :log @var{log} |
| 1880 | Initialize the log function of a server process to @var{log}. The log |
| 1881 | function is called each time the server accepts a network connection |
| 1882 | from a client. The arguments passed to the log function are |
| 1883 | @var{server}, @var{connection}, and @var{message}, where @var{server} |
| 1884 | is the server process, @var{connection} is the new process for the |
| 1885 | connection, and @var{message} is a string describing what has |
| 1886 | happened. |
| 1887 | |
| 1888 | @item :plist @var{plist} |
| 1889 | Initialize the process plist to @var{plist}. |
| 1890 | @end table |
| 1891 | |
| 1892 | The following network options can be specified for the network |
| 1893 | process. Except for @code{:reuseaddr}, you can set or modify these |
| 1894 | options later using @code{set-network-process-option}. |
| 1895 | |
| 1896 | For a server process, the options specified with |
| 1897 | @code{make-network-process} are not inherited by the client |
| 1898 | connections, so you will need to set the necessary options for each |
| 1899 | child connection as they are created. |
| 1900 | |
| 1901 | @table @asis |
| 1902 | @item :bindtodevice @var{device-name} |
| 1903 | If @var{device-name} is a non-empty string identifying a network |
| 1904 | interface name (see @code{network-interface-list}), only handle |
| 1905 | packets received on that interface. If @var{device-name} is @code{nil} |
| 1906 | (the default), handle packets received on any interface. |
| 1907 | |
| 1908 | Using this option may require special privileges on some systems. |
| 1909 | |
| 1910 | @item :broadcast @var{broadcast-flag} |
| 1911 | If @var{broadcast-flag} is non-@code{nil} for a datagram process, the |
| 1912 | process will receive datagram packet sent to a broadcast address, and |
| 1913 | be able to send packets to a broadcast address. Ignored for a stream |
| 1914 | connection. |
| 1915 | |
| 1916 | @item :dontroute @var{dontroute-flag} |
| 1917 | If @var{dontroute-flag} is non-@code{nil}, the process can only send |
| 1918 | to hosts on the same network as the local host. |
| 1919 | |
| 1920 | @item :keepalive @var{keepalive-flag} |
| 1921 | If @var{keepalive-flag} is non-@code{nil} for a stream connection, |
| 1922 | enable exchange of low-level keep-alive messages. |
| 1923 | |
| 1924 | @item :linger @var{linger-arg} |
| 1925 | If @var{linger-arg} is non-@code{nil}, wait for successful |
| 1926 | transmission of all queued packets on the connection before it is |
| 1927 | deleted (see @code{delete-process}). If @var{linger-arg} is an |
| 1928 | integer, it specifies the maximum time in seconds to wait for queued |
| 1929 | packets to be sent before closing the connection. Default is |
| 1930 | @code{nil} which means to discard unsent queued packets when the |
| 1931 | process is deleted. |
| 1932 | |
| 1933 | @item :oobinline @var{oobinline-flag} |
| 1934 | If @var{oobinline-flag} is non-@code{nil} for a stream connection, |
| 1935 | receive out-of-band data in the normal data stream. Otherwise, ignore |
| 1936 | out-of-band data. |
| 1937 | |
| 1938 | @item :priority @var{priority} |
| 1939 | Set the priority for packets sent on this connection to the integer |
| 1940 | @var{priority}. The interpretation of this number is protocol |
| 1941 | specific, such as setting the TOS (type of service) field on IP |
| 1942 | packets sent on this connection. It may also have system dependent |
| 1943 | effects, such as selecting a specific output queue on the network |
| 1944 | interface. |
| 1945 | |
| 1946 | @item :reuseaddr @var{reuseaddr-flag} |
| 1947 | If @var{reuseaddr-flag} is non-@code{nil} (the default) for a stream |
| 1948 | server process, allow this server to reuse a specific port number (see |
| 1949 | @code{:service}) unless another process on this host is already |
| 1950 | listening on that port. If @var{reuseaddr-flag} is @code{nil}, there |
| 1951 | may be a period of time after the last use of that port (by any |
| 1952 | process on the host), where it is not possible to make a new server on |
| 1953 | that port. |
| 1954 | |
| 1955 | @end table |
| 1956 | |
| 1957 | The original argument list, modified with the actual connection |
| 1958 | information, is available via the @code{process-contact} function. |
| 1959 | @end defun |
| 1960 | |
| 1961 | @defun set-network-process-option process option value |
| 1962 | This function sets or modifies a network option for network process |
| 1963 | @var{process}. See @code{make-network-process} for details of options |
| 1964 | @var{option} and their corresponding values @var{value}. |
| 1965 | |
| 1966 | The current setting of an option is available via the |
| 1967 | @code{process-contact} function. |
| 1968 | @end defun |
| 1969 | |
| 1970 | @defun network-interface-list |
| 1971 | This function returns a list describing the network interfaces |
| 1972 | of the machine you are using. The value is an alist whose |
| 1973 | elements have the form @code{(@var{name} . @var{address})}. |
| 1974 | @var{address} has the same form as the @var{local-address} |
| 1975 | and @var{remote-address} arguments to @code{make-network-process}. |
| 1976 | @end defun |
| 1977 | |
| 1978 | @defun network-interface-info ifname |
| 1979 | This function returns information about the network interface named |
| 1980 | @var{ifname}. The value is a list of the form @code{(@var{addr} @var{bcast} @var{netmask} @var{hwaddr} @var{flags})}. |
| 1981 | |
| 1982 | @table @var |
| 1983 | @item addr |
| 1984 | The internet protocol address. |
| 1985 | @item bcast |
| 1986 | The broadcast address. |
| 1987 | @item netmask |
| 1988 | The network mask. |
| 1989 | @item hwaddr |
| 1990 | The layer 2 address (Ethernet MAC address, for instance). |
| 1991 | @item flags |
| 1992 | The current flags of the interface. |
| 1993 | @end table |
| 1994 | @end defun |
| 1995 | |
| 1996 | @defun format-network-address address &optional omit-port |
| 1997 | This function converts the Lisp representation of a network address to |
| 1998 | a string. For example, a five-element vector @code{[@var{a} @var{b} |
| 1999 | @var{c} @var{d} @var{p}]} represents an IP address |
| 2000 | @var{a}.@var{b}.@var{c}.@var{d} and port number @var{p}. |
| 2001 | @code{format-network-address} converts that to the string |
| 2002 | @code{"@var{a}.@var{b}.@var{c}.@var{d}:@var{p}"}. |
| 2003 | |
| 2004 | If @var{omit-port} is non-@code{nil}, the value does not include |
| 2005 | the port number. |
| 2006 | @end defun |
| 2007 | |
| 2008 | To test for the availability of a given network feature, use |
| 2009 | @code{featurep} like this: |
| 2010 | |
| 2011 | @example |
| 2012 | (featurep 'make-network-process '(@var{keyword} @var{value})) |
| 2013 | @end example |
| 2014 | |
| 2015 | @noindent |
| 2016 | The result of the first form is @code{t} if it works to specify |
| 2017 | @var{keyword} with value @var{value} in @code{make-network-process}. |
| 2018 | The result of the second form is @code{t} if @var{keyword} is |
| 2019 | supported by @code{make-network-process}. Here are some of the |
| 2020 | @var{keyword}---@var{value} pairs you can test in |
| 2021 | this way. |
| 2022 | |
| 2023 | @table @code |
| 2024 | @item (:nowait t) |
| 2025 | Non-@code{nil} if non-blocking connect is supported. |
| 2026 | @item (:type datagram) |
| 2027 | Non-@code{nil} if datagrams are supported. |
| 2028 | @item (:family local) |
| 2029 | Non-@code{nil} if local (aka ``UNIX domain'') sockets are supported. |
| 2030 | @item (:service t) |
| 2031 | Non-@code{nil} if the system can select the port for a server. |
| 2032 | @end table |
| 2033 | |
| 2034 | To test for the availability of a given network option, use |
| 2035 | @code{featurep} like this: |
| 2036 | |
| 2037 | @example |
| 2038 | (featurep 'make-network-process '@var{keyword}) |
| 2039 | @end example |
| 2040 | |
| 2041 | Here are some of the option @var{keyword}s you can test in |
| 2042 | this way. |
| 2043 | |
| 2044 | @table @code |
| 2045 | @item :bindtodevice |
| 2046 | @itemx :broadcast |
| 2047 | @itemx :dontroute |
| 2048 | @itemx :keepalive |
| 2049 | @itemx :linger |
| 2050 | @itemx :oobinline |
| 2051 | @itemx :priority |
| 2052 | @itemx :reuseaddr |
| 2053 | That particular network option is supported by |
| 2054 | @code{make-network-process} and @code{set-network-process-option}. |
| 2055 | @end table |
| 2056 | |
| 2057 | @ignore |
| 2058 | arch-tag: ba9da253-e65f-4e7f-b727-08fba0a1df7a |
| 2059 | @end ignore |
| 2060 | |