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/* env.c - manipulate environment and execute a program
in that environment
Mly 861126
Copyright (C) 1986 Free Software Foundation, Inc.
NO WARRANTY
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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:
*/
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