[PATCH 2/2] env: add option -S to split string

[Marc Kewitz]

Hi,
I kind of needed this feature in busybox. Maybe it is already useful in this state


On April 7, 2025 12:08:04 PM GMT+02:00, Marc Kewitz <herderkewitz at googlemail.com> wrote:
>used in cases where no proper argument vector is passed to env
>an example are shebangs:
>"#!/usr/bin/env -S executable -o"
>this will pass 3 arguments to env: the env executable,
>"-S executable -o" as one string and filename.
>"-S executable -o" willobe split and "executable -o" will be separate
>arguments in the argument vector
>---
> coreutils/env.c | 39 ++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 38 insertions(+), 1 deletion(-)
>
>diff --git a/coreutils/env.c b/coreutils/env.c
>index 9ca1fad2d..22cc916be 100644
>--- a/coreutils/env.c
>+++ b/coreutils/env.c
>@@ -48,6 +48,7 @@
> //usage:     "\n	-, -i	Start with empty environment"
> //usage:     "\n	-0	NUL terminated output"
> //usage:     "\n	-u NAME	Remove variable from environment"
>+//usage:     "\n	-S ARGS	split into separate arguments, only useful in shebang or similar"
> 
> #include "libbb.h"
> #include <getopt.h>
>@@ -56,10 +57,11 @@ static struct option const long_options[] = {
> 	{"ignore-environment", no_argument,       0,  'i' },
> 	{"null",               no_argument,       0,  '0' },
> 	{"unset",              required_argument, 0,  'u' },
>+	{"split",              required_argument, 0,  'S' },
> 	{0,                    0,                 0,  0 }
> };
> 
>-static char const short_options[] = "+iu:0";
>+static char const short_options[] = "+iS:u:0";
> 
> static char const **unset_vars;
> static int num_unset_vars;
>@@ -70,6 +72,38 @@ static void add_unset_var (char const *var)
> 	unset_vars[num_unset_vars++] = var;
> }
> 
>+// inspired by GNU core utilities env.c
>+static void split_string (char const *str, int *optind, int *argc, char ***argv)
>+{
>+	// remember the amount of extra arguments after the string to split
>+	int extra_argc = *argc - *optind;
>+	// 1 is reserved for the executable name of env
>+	int new_argc = extra_argc + 1;
>+	int new_ind = new_argc - extra_argc;
>+	char **new_argv = NULL;
>+	char *arg, *tokstate;
>+
>+	// keep it simple, assume arguments are split by spaces
>+	arg = strtok_r (str, " ", &tokstate);
>+	while (arg != NULL) {
>+		// increase size of new_argv
>+		new_argv = xrealloc(new_argv, ++new_argc * sizeof(char *));
>+		// copy the current argument to new_argv
>+		new_argv[new_ind++] = xstrdup(arg);
>+		arg = strtok_r (NULL, " ", &tokstate);
>+	}
>+	// keep executable name
>+	*new_argv = (*argv)[0];
>+
>+	// copy remaining arguments
>+	memcpy(new_argv + new_ind, *argv + *optind, (extra_argc + 1) * sizeof(char *));
>+
>+	// write back values to argc and argv
>+	*argc = new_argc;
>+	*argv = new_argv;
>+	*optind = 0;
>+}
>+
> int env_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
> int env_main(int argc, char **argv)
> {
>@@ -90,6 +124,9 @@ int env_main(int argc, char **argv)
> 		case '0':
> 			null_terminate_output = true;
> 			break;
>+		case 'S':
>+			split_string(optarg, &optind, &argc, &argv);
>+			break;
> 		default:
> 			exit(EXIT_FAILURE);
> 		}
>-- 
>2.30.2
>
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