shadow/libmisc/shell.c

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/*
* Copyright 1989 - 1991, Julianne Frances Haugh
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Julianne F. Haugh nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JULIE HAUGH AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL JULIE HAUGH OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <config.h>
#include "rcsid.h"
RCSID("$Id: shell.c,v 1.7 1998/12/28 20:34:53 marekm Exp $")
#include <stdio.h>
#include <errno.h>
#include "prototypes.h"
#include "defines.h"
extern char **newenvp;
extern size_t newenvc;
/*
* shell - execute the named program
*
* shell begins by trying to figure out what argv[0] is going to
* be for the named process. The user may pass in that argument,
* or it will be the last pathname component of the file with a
* '-' prepended. The first attempt is to just execute the named
* file. If the errno comes back "ENOEXEC", the file is assumed
* at first glance to be a shell script. The first two characters
* must be "#!", in which case "/bin/sh" is executed to process
* the file. If all that fails, give up in disgust ...
*/
void
shell(const char *file, const char *arg)
{
char arg0[1024];
int err;
if (file == (char *) 0)
exit (1);
/*
* The argv[0]'th entry is usually the path name, but
* for various reasons the invoker may want to override
* that. So, we determine the 0'th entry only if they
* don't want to tell us what it is themselves.
*/
if (arg == (char *) 0) {
snprintf(arg0, sizeof arg0, "-%s", Basename((char *) file));
arg = arg0;
}
#ifdef DEBUG
printf (_("Executing shell %s\n"), file);
#endif
/*
* First we try the direct approach. The system should be
* able to figure out what we are up to without too much
* grief.
*/
execle (file, arg, (char *) 0, newenvp);
err = errno;
/* Linux handles #! in the kernel, and bash doesn't make
sense of "#!" so it wouldn't work anyway... --marekm */
#ifndef __linux__
/*
* It is perfectly OK to have a shell script for a login
* shell, and this code attempts to support that. It
* relies on the standard shell being able to make sense
* of the "#!" magic number.
*/
if (err == ENOEXEC) {
FILE *fp;
if ((fp = fopen (file, "r"))) {
if (getc (fp) == '#' && getc (fp) == '!') {
fclose (fp);
execle ("/bin/sh", "sh",
file, (char *) 0, newenvp);
err = errno;
} else {
fclose (fp);
}
}
}
#endif
/*
* Obviously something is really wrong - I can't figure out
* how to execute this stupid shell, so I might as well give
* up in disgust ...
*/
snprintf(arg0, sizeof arg0, _("Cannot execute %s"), file);
errno = err;
perror(arg0);
exit(1);
}