From 27433dabe003ea61dde224b25559758619ac4cdf Mon Sep 17 00:00:00 2001
From: "Jan (janneke) Nieuwenhuizen" <janneke@gnu.org>
Date: Wed, 2 Nov 2022 07:34:39 +0100
Subject: [PATCH] DRAFT lib: Implement system.

* lib/stub/system.c: Move to...
* lib/stdlib/system.c: ...here.  Implement.
* build-aux/configure-lib.sh (libc_gnu_SOURCES): Update file name.
* include/stdlib.h (system): Add prototype.
---
 build-aux/configure-lib.sh    |  2 +-
 include/stdlib.h              |  3 ++-
 lib/{stub => stdlib}/system.c | 42 ++++++++++++++++++++++++++++-------
 3 files changed, 37 insertions(+), 10 deletions(-)
 rename lib/{stub => stdlib}/system.c (52%)

diff --git a/build-aux/configure-lib.sh b/build-aux/configure-lib.sh
index 13b06083..6488d2c4 100644
--- a/build-aux/configure-lib.sh
+++ b/build-aux/configure-lib.sh
@@ -353,6 +353,7 @@ lib/stdlib/atexit.c
 lib/stdlib/atof.c
 lib/stdlib/atol.c
 lib/stdlib/mbstowcs.c
+lib/stdlib/system.c
 lib/string/bcmp.c
 lib/string/bcopy.c
 lib/string/bzero.c
@@ -406,7 +407,6 @@ lib/stub/strftime.c
 lib/stub/strsignal.c
 lib/stub/sys_siglist.c
 lib/stub/sysconf.c
-lib/stub/system.c
 lib/stub/times.c
 lib/stub/ttyname.c
 lib/stub/umask.c
diff --git a/include/stdlib.h b/include/stdlib.h
index fe9d574d..3fec7e06 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -1,6 +1,6 @@
 /* -*-comment-start: "//";comment-end:""-*-
  * GNU Mes --- Maxwell Equations of Software
- * Copyright © 2017,2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2017,2018,2019,2022 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
  *
  * This file is part of GNU Mes.
  *
@@ -59,6 +59,7 @@ long strtol (char const *string, char **tailptr, int base);
 long long strtoll (char const *string, char **tailptr, int base);
 unsigned long strtoul (char const *string, char **tailptr, int base);
 unsigned long long strtoull (char const *string, char **tailptr, int base);
+int system (char const *command);
 
 #define EXIT_FAILURE 1
 #define EXIT_SUCCESS 0
diff --git a/lib/stub/system.c b/lib/stdlib/system.c
similarity index 52%
rename from lib/stub/system.c
rename to lib/stdlib/system.c
index 49663fb0..34b4546f 100644
--- a/lib/stub/system.c
+++ b/lib/stdlib/system.c
@@ -1,6 +1,6 @@
 /* -*-comment-start: "//";comment-end:""-*-
  * GNU Mes --- Maxwell Equations of Software
- * Copyright © 2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2018,2022 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
  *
  * This file is part of GNU Mes.
  *
@@ -20,14 +20,40 @@
 
 #include <mes/lib.h>
 #include <errno.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#ifndef SHELL_FILE_NAME
+#define	SHELL_FILE_NAME "/bin/sh"
+#endif
+#ifndef SHELL_COMMAND_NAME
+#define	SHELL_COMMAND_NAME "sh"
+#endif
 
 int
-system (int x)
+system (char const *command)
 {
-  static int stub = 0;
-  if (__mes_debug () && !stub)
-    eputs ("system stub\n");
-  stub = 1;
-  errno = 0;
-  return 0;
+  pid_t pid = fork ();
+  if (pid == -1)
+    return -1;
+  else if (pid == 0)
+    {
+      // child
+      char const *argv[4];
+      argv[0] = SHELL_COMMAND_NAME;
+      argv[1] = "-c";
+      argv[2] = command;
+      argv[3] = 0;
+      execve (SHELL_FILE_NAME, (char *const *) argv, environ);
+      _exit (127);
+    }
+
+  // parent
+  int status;
+  pid_t child_pid = waitpid (pid, &status, 0);
+  if (child_pid != pid)
+    return -1;
+
+  return status;
 }