gnu1987/gnucmds/env.c

/* env.c - manipulate environment and execute a program
   in that environment
   Mly 861126 */

/* Copyright (C) 1986, Free Software Foundation, Inc.

		       NO WARRANTY

  BECAUSE THIS PROGRAM IS LICENSED FREE OF CHARGE, WE PROVIDE ABSOLUTELY
NO WARRANTY, TO THE EXTENT PERMITTED BY APPLICABLE STATE LAW.  EXCEPT
WHEN OTHERWISE STATED IN WRITING, FREE SOFTWARE FOUNDATION, INC,
RICHARD M. STALLMAN AND/OR OTHER PARTIES PROVIDE THIS PROGRAM "AS IS"
WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING,
BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY
AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE PROGRAM PROVE
DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
CORRECTION.

 IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW WILL RICHARD M.
STALLMAN, THE FREE SOFTWARE FOUNDATION, INC., AND/OR ANY OTHER PARTY
WHO MAY MODIFY AND REDISTRIBUTE THIS PROGRAM AS PERMITTED BELOW, BE
LIABLE TO YOU FOR DAMAGES, INCLUDING ANY LOST PROFITS, LOST MONIES, OR
OTHER SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
USE OR INABILITY TO USE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR
DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY THIRD PARTIES OR
A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS) THIS
PROGRAM, EVEN IF YOU HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
DAMAGES, OR FOR ANY CLAIM BY ANY OTHER PARTY.

		GENERAL PUBLIC LICENSE TO COPY

  1. You may copy and distribute verbatim copies of this source file
as you receive it, in any medium, provided that you conspicuously
and appropriately publish on each copy a valid copyright notice
"Copyright (C) 1986 Free Software Foundation"; and include
following the copyright notice a verbatim copy of the above disclaimer
of warranty and of this License.

  2. You may modify your copy or copies of this source file or
any portion of it, and copy and distribute such modifications under
the terms of Paragraph 1 above, provided that you also do the following:

    a) cause the modified files to carry prominent notices stating
    that you changed the files and the date of any change; and

    b) cause the whole of any work that you distribute or publish,
    that in whole or in part contains or is a derivative of this
    program or any part thereof, to be freely distributed
    and licensed to all third parties on terms identical to those
    contained in this License Agreement (except that you may choose
    to grant more extensive warranty protection to third parties,
    at your option).

  3. You may copy and distribute this program or any portion of it in
compiled, executable or object code form under the terms of Paragraphs
1 and 2 above provided that you do the following:

    a) cause each such copy to be accompanied by the
    corresponding machine-readable source code, which must
    be distributed under the terms of Paragraphs 1 and 2 above; or,

    b) cause each such copy to be accompanied by a
    written offer, with no time limit, to give any third party
    free (except for a nominal shipping charge) a machine readable
    copy of the corresponding source code, to be distributed
    under the terms of Paragraphs 1 and 2 above; or,

    c) in the case of a recipient of this program in compiled, executable
    or object code form (without the corresponding source code) you
    shall cause copies you distribute to be accompanied by a copy
    of the written offer of source code which you received along
    with the copy you received.

  4. You may not copy, sublicense, distribute or transfer this program
except as expressly provided under this License Agreement.  Any attempt
otherwise to copy, sublicense, distribute or transfer this program is void and
your rights to use the program under this License agreement shall be
automatically terminated.  However, parties who have received computer
software programs from you with this License Agreement will not have
their licenses terminated so long as such parties remain in full compliance.

 In other words, you are welcome to use, share and improve this program.
 You are forbidden to forbid anyone else to use, share and improve
 what you give them.   Help stamp out software-hoarding!  */

/* 

   If first argument is "-", then a new environment is constructed
   from scratch; otherwise the environment is inherited from the parent
   process, except as modified by other options.
   
   So, "env - foo" will invoke the "foo" program in a null environment,
   whereas "env foo" would invoke "foo" in the same environment as that
   passed to "env" itself.

   Subsequent arguments are interpreted as follows:
   
   * "variable=value" (ie an arg containing a "=" character)
     means to set the specified environment variable to that value.
     `value' may be of zero length ("variable=").  Note that setting
     a variable to a zero-length value is different from unsetting it.

   * "-u variable" or "-unset variable"
     means to unset that variable
     If that variable isn't set, does nothing.

   * "-s variable value" or "-set variable value"
     same as "variable=value"

   * "-" or "--"
     are used to indicate that the following argument is the program
     to invoke.  This is only necessary when the program's name
     begins with "-" or contains a "="

   * anything else
     The first remaining argument specifies a program to invoke
     (it is searched for according to the specification of the PATH
     environment variable) and any arguments following that are
     passed as arguments to that program

     If no program-name is specified following the environment
     specifications the the resulting environment is printed
     (The is like specifying a program-name of "printenv")

   Examples:
     If the environment passed to "env" is
     { USER=rms EDITOR=emacs PATH=.:/gnubin:/hacks }

     * "env DISPLAY=gnu:0 nemacs"
        calls "nemacs" in the envionment
	{ EDITOR=emacs USER=rms DISPLAY=gnu }

     * "env - USER=foo /hacks/hack bar baz"
       will call the "hack" program on arguments "bar" and "baz"
       in an environment in which the only variable is "USER"
       Note that the "-" option will clear out the PATH variable,
       so one should be careful to specify in which directory
       to find the program to call
       
     * "env -u EDITOR USER=foo PATH=/energy -- e=mc2 bar baz"
       The program "/energy/e=mc2" is called with environment
       { USER=foo PATH=/energy }

*/

#ifdef EMACS
#define NO_SHORTNAMES
#include "../src/config.h"
#endif /* EMACS */

#include <stdio.h>

extern int execvp ();
extern char *index ();

char *xmalloc (), *xrealloc ();
char *concat ();

extern char **environ;

char **nenv;
int nenv_size;

char *progname;
void setenv ();
void fatal ();

main (argc, argv, envp)
     register int argc;
     register char **argv;
     char **envp;
{
  register char *tem;

  progname = argv[0];
  argc--;
  argv++;

  nenv_size = 100;
  nenv = (char **) xmalloc (nenv_size * sizeof (char *));
  *nenv = (char *) 0;

  /* "-" flag means to not inherit parent's environment */
  if (argc && !strcmp (*argv, "-"))
    {
      argc--;
      argv++;
    }
  else
    /* Else pass on existing env vars. */
    for (; *envp; envp++)
      {
	tem = index (*envp, '=');
	if (tem)
	  {
	    *tem = '\000';
	    setenv (*envp, tem + 1);
	  }
     }

  while (argc > 0)
    {
      tem = index (*argv, '=');
      if (tem)
	/* If arg contains a "=" it specifies to set a variable */
	{
	  *tem = '\000';
	  setenv (*argv, tem + 1);
	  argc--; argv++;
	  continue;
	}
      
      if (**argv != '-')
	/* Remaining args are program name and args to pass it */
	break;

      if (argc < 2)
	fatal ("No argument following \"%s\" switch", *argv);
       if (!strcmp (*argv, "-u") ||
	       !strcmp (*argv, "-unset"))
	/* Unset a variable */
	{
	  argc--; argv++;
	  setenv (*argv, 0);
	  argc--; argv++;
	}
      else if (!strcmp (*argv, "-s") ||
	       !strcmp (*argv, "-set"))
	/* Set a variable */
	{
	  argc--; argv++;
	  tem = *argv;
	  if (argc < 2)
	    fatal ("No value specified for variable \"%s\"",
		   tem);
	  argc--; argv++;
	  setenv (tem, *argv);
	  argc--; argv++;
	}
      else if (!strcmp (*argv, "-") || !strcmp (*argv, "--"))
	{
	  argc--; argv++;
	  break;
	}
      else
	{
	  fatal ("unknown switch \"%s\"", *argv);
	}
    }

  /* If no program specified print the environment and exit */
  if (argc <= 0)
    {
      while (*nenv)
	printf ("%s\n", *nenv++);
      exit (0);
    }
  else
    {
      extern int errno, sys_nerr;
      extern char *sys_errlist[];

      environ = nenv;
      (void) execvp (*argv, argv);

      fprintf (stderr, "%s: Cannot execute \"%s\"",
	       progname, *argv);
      if (errno < sys_nerr)
	fprintf (stderr, ": %s\n" , sys_errlist[errno]);
      else
	putc ('\n', stderr);
      exit (errno != 0 ? errno : 1);
    }
}

void
setenv (var, val)
  register char *var, *val;
{
  register char **e;
  int len = strlen (var);

  {
    register char *tem = index (var, '=');
    if (tem)
      fatal ("Environment variable names may not contain \"=\": %s",
	     var);
    else if (*var == '\000')
      fatal ("Zero-length environment variable name specified.");
  }

  for (e = nenv; *e; e++)
    if (!strncmp (var, *e, len) &&
	(*e)[len] == '=')
      {
	if (val)
	  goto set;
	else
	  do { *e = *(e + 1); } while (*e++);
	return;
      }

  if (!val)
    return; /* Nothing to unset */

  len = e - nenv;
  if (len + 1 >= nenv_size)
    {
      nenv_size += 100;
      nenv = (char **) xrealloc (nenv, nenv_size * sizeof (char *));
      e = nenv + len;
    }

 set:
  val = concat (var, "=", val);
  if (*e)
    free (*e);
  else
    *(e + 1) = (char *) 0;
  *e = val;
  return;
}

void
fatal (msg, arg1, arg2)
     char *msg, *arg1, *arg2;
{
  fprintf (stderr, "%s: ", progname);
  fprintf (stderr, msg, arg1, arg2);
  putc ('\n', stderr);
  exit (1);
}


extern char *malloc (), *realloc ();

void
memory_fatal ()
{
  fatal ("Out of memory");
}

char *
xmalloc (size)
     int size;
{
  register char *value;
  value = (char *) malloc (size);
  if (!value) memory_fatal ();
  return (value);
}

char *
xrealloc (ptr, size)
     char *ptr;
     int size;
{
  register char *value;
  value = (char *) realloc (ptr, size);
  if (!value) memory_fatal ();
  return (value);
}

/* Return a newly-allocated string whose contents concatenate those of s1, s2, s3.  */

char *
concat (s1, s2, s3)
     char *s1, *s2, *s3;
{
  int len1 = strlen (s1), len2 = strlen (s2), len3 = strlen (s3);
  char *result = (char *) xmalloc (len1 + len2 + len3 + 1);

  strcpy (result, s1);
  strcpy (result + len1, s2);
  strcpy (result + len1 + len2, s3);
  *(result + len1 + len2 + len3) = 0;

  return result;
}


/*
 * Local variables:
 * compile-command: "cc -g -o env env.c"
 * end:
 */