>From b331bbaf4eb0581fce24f078561283e3616398f8 Mon Sep 17 00:00:00 2001
From: Bruno Haible <bruno@clisp.org>
Date: Fri, 23 Sep 2022 02:36:48 +0200
Subject: [PATCH] syscmd: Make it work again for most commands on FreeBSD and
 AIX.

* src/builtin.c (m4_syscmd): Use "sh -c -- $cmd" only if $cmd starts with
'-' or '+'.
---
 src/builtin.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/builtin.c b/src/builtin.c
index 0715a332..0180d625 100644
--- a/src/builtin.c
+++ b/src/builtin.c
@@ -947,7 +947,7 @@ m4_syscmd (struct obstack *obs MAYBE_UNUSED, int argc, token_data **argv)
   const char *cmd = ARG (1);
   int status;
   int sig_status;
-  int slot = 3;
+  int slot;
   const char *prog_args[5] = { "sh", "-c", "--" };
   if (bad_argc (argv[0], argc, 2, 2) || !*cmd)
     {
@@ -964,8 +964,23 @@ m4_syscmd (struct obstack *obs MAYBE_UNUSED, int argc, token_data **argv)
       prog_args[1] = "/c";
       slot = 2;
     }
+  else
 #endif
+    {
+      if (cmd[0] == '-' || cmd[0] == '+')
+        /* If cmd starts with '-' or '+', "sh -c $cmd" is not guaranteed to
+           work.  In this case, use "sh -c -- $cmd".
+           Note: This requires a POSIX compliant SYSCMD_SHELL.  It does not
+           work with /bin/sh on FreeBSD 13 and AIX 7, and on these platforms
+           'bash' is not guaranteed to be installed.  */
+        slot = 3;
+      else
+        /* For most commands, the traditional "sh -c $cmd" works fine.
+           Including on FreeBSD 13 and AIX 7.  */
+        slot = 2;
+    }
   prog_args[slot] = cmd;
+  prog_args[slot + 1] = NULL;
   errno = 0;
   status = execute (ARG (0), SYSCMD_SHELL, prog_args, NULL, false,
                     false, false, false, true, false, &sig_status);
-- 
2.34.1