[PATCH] env: add -n/--name option

[Matheus Afonso Martins Moreira]

Sets the zeroth argument (argv[0]) of the invoked command.
It's difficult to use bash's exec -a simultaneously with env,
so add support for setting the program name with env.

Discussed in: https://lists.gnu.org/r/coreutils/2023-03/msg00002.html

* src/env.c (newname, program): New variables, options and logic.
---
 src/env.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/env.c b/src/env.c
index 2f38d75..3dc5c2a 100644
--- a/src/env.c
+++ b/src/env.c
@@ -76,7 +76,7 @@ static bool report_signal_handling;
 /* The isspace characters in the C locale.  */
 #define C_ISSPACE_CHARS " \t\n\v\f\r"
 
-static char const shortopts[] = "+C:iS:u:v0" C_ISSPACE_CHARS;
+static char const shortopts[] = "+C:n:iS:u:v0" C_ISSPACE_CHARS;
 
 /* For long options that have no equivalent short option, use a
    non-character as a pseudo short option, starting with CHAR_MAX + 1.  */
@@ -94,6 +94,7 @@ static struct option const longopts[] =
   {"null", no_argument, NULL, '0'},
   {"unset", required_argument, NULL, 'u'},
   {"chdir", required_argument, NULL, 'C'},
+  {"name", required_argument, NULL, 'n'},
   {"default-signal", optional_argument, NULL, DEFAULT_SIGNAL_OPTION},
   {"ignore-signal",  optional_argument, NULL, IGNORE_SIGNAL_OPTION},
   {"block-signal",   optional_argument, NULL, BLOCK_SIGNAL_OPTION},
@@ -128,6 +129,9 @@ Set each NAME to VALUE in the environment and run 
COMMAND.\n\
 "), stdout);
       fputs (_("\
   -C, --chdir=DIR      change working directory to DIR\n\
+"), stdout);
+      fputs (_("\
+  -n, --name=NAME      pass NAME as the zeroth argument of COMMAND\n\
 "), stdout);
       fputs (_("\
   -S, --split-string=S  process and split S into separate arguments;\n\
@@ -754,6 +758,7 @@ main (int argc, char **argv)
   bool ignore_environment = false;
   bool opt_nul_terminate_output = false;
   char const *newdir = NULL;
+  char *newname = NULL;
 
   initialize_main (&argc, &argv);
   set_program_name (argv[0]);
@@ -798,6 +803,9 @@ main (int argc, char **argv)
         case 'C':
           newdir = optarg;
           break;
+        case 'n':
+          newname = optarg;
+          break;
         case 'S':
           parse_split_string (optarg, &optind, &argc, &argv);
           break;
@@ -860,6 +868,12 @@ main (int argc, char **argv)
       usage (EXIT_CANCELED);
     }
 
+  if (newname && ! program_specified)
+    {
+      error (0, 0, _("must specify command with --name (-n)"));
+      usage (EXIT_CANCELED);
+    }
+
   if (! program_specified)
     {
       /* Print the environment and exit.  */
@@ -885,6 +899,13 @@ main (int argc, char **argv)
              quoteaf (newdir));
     }
 
+  char *program = argv[optind];
+  if (newname)
+    {
+      devmsg ("name:     %s\n", quoteaf (newname));
+      argv[optind] = newname;
+    }
+
   if (dev_debug)
     {
       devmsg ("executing: %s\n", argv[optind]);
@@ -892,7 +913,7 @@ main (int argc, char **argv)
         devmsg ("   arg[%d]= %s\n", i-optind, quote (argv[i]));
     }
 
-  execvp (argv[optind], &argv[optind]);
+  execvp (program, &argv[optind]);
 
   int exit_status = errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE;
   error (0, errno, "%s", quote (argv[optind]));
-- 
2.39.2