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Jim Blandy
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1 changed files with 338 additions and 0 deletions
338
lib-src/env.c
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338
lib-src/env.c
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/* env - manipulate environment and execute a program in that environment
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Copyright (C) 1986 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
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/* Mly 861126 */
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/* If first argument is "-", then a new environment is constructed
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from scratch; otherwise the environment is inherited from the parent
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process, except as modified by other options.
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So, "env - foo" will invoke the "foo" program in a null environment,
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whereas "env foo" would invoke "foo" in the same environment as that
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passed to "env" itself.
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Subsequent arguments are interpreted as follows:
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* "variable=value" (i.e., an arg containing a "=" character)
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means to set the specified environment variable to that value.
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`value' may be of zero length ("variable="). Note that setting
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a variable to a zero-length value is different from unsetting it.
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* "-u variable" or "-unset variable"
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means to unset that variable.
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If that variable isn't set, does nothing.
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* "-s variable value" or "-set variable value"
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same as "variable=value".
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* "-" or "--"
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are used to indicate that the following argument is the program
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to invoke. This is only necessary when the program's name
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begins with "-" or contains a "=".
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* anything else
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The first remaining argument specifies a program to invoke
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(it is searched for according to the specification of the PATH
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environment variable) and any arguments following that are
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passed as arguments to that program.
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If no program-name is specified following the environment
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specifications, the resulting environment is printed.
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This is like specifying a program-name of "printenv".
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Examples:
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If the environment passed to "env" is
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{ USER=rms EDITOR=emacs PATH=.:/gnubin:/hacks }
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* "env DISPLAY=gnu:0 nemacs"
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calls "nemacs" in the envionment
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{ USER=rms EDITOR=emacs PATH=.:/gnubin:/hacks DISPLAY=gnu:0 }
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* "env - USER=foo /hacks/hack bar baz"
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calls the "hack" program on arguments "bar" and "baz"
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in an environment in which the only variable is "USER".
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Note that the "-" option clears out the PATH variable,
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so one should be careful to specify in which directory
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to find the program to call.
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* "env -u EDITOR USER=foo PATH=/energy -- e=mc2 bar baz"
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The program "/energy/e=mc2" is called with environment
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{ USER=foo PATH=/energy }
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*/
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#ifdef EMACS
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#define NO_SHORTNAMES
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#include "../src/config.h"
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#endif /* EMACS */
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#include <stdio.h>
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extern int execvp ();
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char *xmalloc (), *xrealloc ();
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char *concat ();
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extern char **environ;
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char **nenv;
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int nenv_size;
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char *progname;
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void setenv ();
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void fatal ();
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char *myindex ();
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main (argc, argv, envp)
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register int argc;
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register char **argv;
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char **envp;
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{
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register char *tem;
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progname = argv[0];
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argc--;
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argv++;
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nenv_size = 100;
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nenv = (char **) xmalloc (nenv_size * sizeof (char *));
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*nenv = (char *) 0;
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/* "-" flag means to not inherit parent's environment */
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if (argc && !strcmp (*argv, "-"))
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{
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argc--;
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argv++;
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}
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else
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/* Else pass on existing env vars. */
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for (; *envp; envp++)
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{
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tem = myindex (*envp, '=');
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if (tem)
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{
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*tem = '\000';
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setenv (*envp, tem + 1);
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}
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}
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while (argc > 0)
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{
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tem = myindex (*argv, '=');
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if (tem)
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/* If arg contains a "=" it specifies to set a variable */
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{
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*tem = '\000';
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setenv (*argv, tem + 1);
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argc--;
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argv++;
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continue;
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}
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if (**argv != '-')
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/* Remaining args are program name and args to pass it */
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break;
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if (argc < 2)
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fatal ("no argument for `%s' option", *argv);
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if (!strcmp (*argv, "-u")
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|| !strcmp (*argv, "-unset"))
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/* Unset a variable */
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{
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argc--;
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argv++;
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setenv (*argv, (char *) 0);
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argc--;
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argv++;
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}
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else if (!strcmp (*argv, "-s") ||
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!strcmp (*argv, "-set"))
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/* Set a variable */
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{
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argc--;
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argv++;
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tem = *argv;
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if (argc < 2)
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fatal ("no value specified for variable \"%s\"", tem);
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argc--;
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argv++;
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setenv (tem, *argv);
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argc--;
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argv++;
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}
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else if (!strcmp (*argv, "-") || !strcmp (*argv, "--"))
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{
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argc--;
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argv++;
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break;
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}
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else
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{
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fatal ("unrecognized option `%s'", *argv);
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}
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}
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/* If no program specified print the environment and exit */
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if (argc <= 0)
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{
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while (*nenv)
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printf ("%s\n", *nenv++);
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exit (0);
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}
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else
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{
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extern int errno, sys_nerr;
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extern char *sys_errlist[];
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environ = nenv;
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(void) execvp (*argv, argv);
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fprintf (stderr, "%s: cannot execute `%s'", progname, *argv);
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if (errno < sys_nerr)
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fprintf (stderr, ": %s\n", sys_errlist[errno]);
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else
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putc ('\n', stderr);
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exit (errno != 0 ? errno : 1);
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}
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}
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void
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setenv (var, val)
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register char *var, *val;
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{
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register char **e;
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int len = strlen (var);
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{
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register char *tem = myindex (var, '=');
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if (tem)
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fatal ("environment variable names can not contain `=': %s", var);
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else if (*var == '\000')
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fatal ("zero-length environment variable name specified");
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}
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for (e = nenv; *e; e++)
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if (!strncmp (var, *e, len) && (*e)[len] == '=')
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{
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if (val)
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goto set;
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else
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do
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{
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*e = *(e + 1);
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} while (*e++);
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return;
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}
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if (!val)
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return; /* Nothing to unset */
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len = e - nenv;
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if (len + 1 >= nenv_size)
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{
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nenv_size += 100;
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nenv = (char **) xrealloc (nenv, nenv_size * sizeof (char *));
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e = nenv + len;
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}
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set:
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val = concat (var, "=", val);
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if (*e)
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free (*e);
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else
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*(e + 1) = (char *) 0;
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*e = val;
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return;
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}
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void
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fatal (msg, arg1, arg2)
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char *msg, *arg1, *arg2;
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{
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fprintf (stderr, "%s: ", progname);
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fprintf (stderr, msg, arg1, arg2);
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putc ('\n', stderr);
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exit (1);
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}
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extern char *malloc (), *realloc ();
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void
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memory_fatal ()
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{
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fatal ("virtual memory exhausted");
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}
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char *
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xmalloc (size)
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int size;
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{
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register char *value;
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value = (char *) malloc (size);
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if (!value)
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memory_fatal ();
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return (value);
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}
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char *
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xrealloc (ptr, size)
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char *ptr;
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int size;
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{
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register char *value;
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value = (char *) realloc (ptr, size);
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if (!value)
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memory_fatal ();
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return (value);
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}
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/* Return a newly-allocated string whose contents concatenate
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those of S1, S2, S3. */
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char *
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concat (s1, s2, s3)
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char *s1, *s2, *s3;
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{
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int len1 = strlen (s1), len2 = strlen (s2), len3 = strlen (s3);
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char *result = (char *) xmalloc (len1 + len2 + len3 + 1);
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strcpy (result, s1);
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strcpy (result + len1, s2);
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strcpy (result + len1 + len2, s3);
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result[len1 + len2 + len3] = 0;
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return result;
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}
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/* Return a pointer to the first occurrence in STR of C,
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or 0 if C does not occur. */
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char *
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myindex (str, c)
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char *str;
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char c;
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{
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char *s = str;
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while (*s)
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{
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if (*s == c)
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return s;
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s++;
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}
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return 0;
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}
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