From 0db17ef9abd59da51ebc30d90fb2dc482b02a4a1 Mon Sep 17 00:00:00 2001
From: Rob Browning <rlb@defaultvalue.org>
Date: Wed, 19 Nov 2003 21:40:32 +0000
Subject: [PATCH] (scm_system_star): new function.

---
 libguile/simpos.c | 117 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 115 insertions(+), 2 deletions(-)

diff --git a/libguile/simpos.c b/libguile/simpos.c
index c9c83935c..caeb753c4 100644
--- a/libguile/simpos.c
+++ b/libguile/simpos.c
@@ -39,13 +39,18 @@
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif
+#if HAVE_SYS_WAIT_H
+# include <sys/wait.h>
+#endif
+
+#include "posix.h"
 
 
 extern int system();
 
 
 #ifdef HAVE_SYSTEM
-SCM_DEFINE (scm_system, "system", 0, 1, 0, 
+SCM_DEFINE (scm_system, "system", 0, 1, 0,
            (SCM cmd),
 	    "Execute @var{cmd} using the operating system's \"command\n"
 	    "processor\".  Under Unix this is usually the default shell\n"
@@ -63,7 +68,7 @@ SCM_DEFINE (scm_system, "system", 0, 1, 0,
     {
       rv = system (NULL);
       return SCM_BOOL(rv);
-    }
+    }  
   SCM_VALIDATE_STRING (1, cmd);
   errno = 0;
   rv = system (SCM_STRING_CHARS (cmd));
@@ -74,6 +79,114 @@ SCM_DEFINE (scm_system, "system", 0, 1, 0,
 #undef FUNC_NAME
 #endif /* HAVE_SYSTEM */
 
+
+#ifdef HAVE_SYSTEM
+#ifdef HAVE_WAITPID
+
+/* return a newly allocated array of char pointers to each of the strings
+   in args, with a terminating NULL pointer.  */
+/* Note: a similar function is defined in dynl.c, but we don't necessarily
+   want to export it.  */
+static char **
+allocate_string_pointers (SCM args)
+{
+  char **result;
+  int n_args = scm_ilength (args);
+  int i;
+
+  SCM_ASSERT (n_args >= 0, args, SCM_ARGn, "allocate_string_pointers");
+  result = (char **) scm_malloc ((n_args + 1) * sizeof (char *));
+  result[n_args] = NULL;
+  for (i = 0; i < n_args; i++)
+    {
+      SCM car = SCM_CAR (args);
+
+      if (!SCM_STRINGP (car))
+	{
+	  free (result);
+	  scm_wrong_type_arg ("allocate_string_pointers", SCM_ARGn, car);
+	}
+      result[i] = SCM_STRING_CHARS (SCM_CAR (args));
+      args = SCM_CDR (args);
+    }
+  return result;
+}
+
+SCM_DEFINE (scm_system_star, "system*", 0, 0, 1,
+           (SCM args),
+"Execute the command indicated by @var{args}.  The first element must\n"
+"be a string indicating the command to be executed, and the remaining\n"
+"items must be strings representing each of the arguments to that\n"
+"command.\n"
+"\n"
+"This function returns the exit status of the command as provided by\n"
+"@code{waitpid}.  This value can be handled with @code{status:exit-val}\n"
+"and the related functions.\n"
+"\n"
+"@code{system*} is similar to @code{system}, but accepts only one\n"
+"string per-argument, and performs no shell interpretation.  The\n"
+"command is executed using fork and execlp.  Accordingly this function\n"
+"may be safer than @code{system} in situations where shell\n"
+"interpretation is not required.\n"
+"\n"
+"Example: (system* \"echo\" \"foo\" \"bar\")")
+#define FUNC_NAME s_scm_system_star
+{
+  if (SCM_NULLP (args))
+    SCM_WRONG_NUM_ARGS ();
+
+  if (SCM_CONSP (args))
+    {
+      SCM oldint;
+      SCM oldquit;
+      SCM sig_ign;
+      SCM sigint;
+      SCM sigquit;
+      int pid;
+      char **execargv;
+
+      SCM_VALIDATE_STRING (1, SCM_CAR (args));
+      /* allocate before fork */
+      execargv = allocate_string_pointers (args);
+
+      /* make sure the child can't kill us (as per normal system call) */
+      sig_ign = scm_long2num ((long) SIG_IGN);
+      sigint = scm_long2num (SIGINT);
+      sigquit = scm_long2num (SIGQUIT);
+      oldint = scm_sigaction (sigint, sig_ign, SCM_UNDEFINED);
+      oldquit = scm_sigaction (sigquit, sig_ign, SCM_UNDEFINED);
+      
+      pid = fork ();
+      if (pid == -1)
+        SCM_SYSERROR;
+      else if (pid)
+        {
+          int wait_result;
+          int status;
+          SCM_SYSCALL (wait_result = waitpid (pid, &status, 0));
+          if (wait_result == -1) SCM_SYSERROR;
+          scm_sigaction (sigint, SCM_CAR (oldint), SCM_CDR (oldint));
+          scm_sigaction (sigquit, SCM_CAR (oldquit), SCM_CDR (oldquit));
+          scm_remember_upto_here_2 (oldint, oldquit);
+          return SCM_MAKINUM (0L + status);
+        }
+      else
+        {
+          execvp (SCM_STRING_CHARS (SCM_CAR (args)), execargv);
+          scm_remember_upto_here_1 (args);
+          SCM_SYSERROR;
+          /* not reached.  */
+          return SCM_BOOL_F;
+        }
+    }
+  else
+    SCM_WRONG_TYPE_ARG (1, SCM_CAR (args));
+}
+#undef FUNC_NAME
+#endif /* HAVE_WAITPID */
+#endif /* HAVE_SYSTEM */
+
+
 SCM_DEFINE (scm_getenv, "getenv", 1, 0, 0, 
             (SCM nam),
 	    "Looks up the string @var{name} in the current environment.  The return\n"
-- 
2.20.1