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+/* env.c - manipulate environment and execute a program
+ in that environment
+ Mly 861126
+
+ Copyright (C) 1986 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 1, or (at your option)
+ any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ 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>
+#include <errno.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:
+ */
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