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Annotation of GNUtools/emacs/etc/env.c, revision 1.1

1.1     ! root        1: /* env.c - manipulate environment and execute a program
        !             2:    in that environment
        !             3:    Mly 861126
        !             4: 
        !             5:    Copyright (C) 1986 Free Software Foundation, Inc.
        !             6: 
        !             7:     This program is free software; you can redistribute it and/or modify
        !             8:     it under the terms of the GNU General Public License as published by
        !             9:     the Free Software Foundation; either version 1, or (at your option)
        !            10:     any later version.
        !            11: 
        !            12:     This program is distributed in the hope that it will be useful,
        !            13:     but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            14:     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        !            15:     GNU General Public License for more details.
        !            16: 
        !            17:     You should have received a copy of the GNU General Public License
        !            18:     along with this program; if not, write to the Free Software
        !            19:     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
        !            20: 
        !            21:  In other words, you are welcome to use, share and improve this program.
        !            22:  You are forbidden to forbid anyone else to use, share and improve
        !            23:  what you give them.   Help stamp out software-hoarding!  */
        !            24: 
        !            25: /* 
        !            26: 
        !            27:    If first argument is "-", then a new environment is constructed
        !            28:    from scratch; otherwise the environment is inherited from the parent
        !            29:    process, except as modified by other options.
        !            30:    
        !            31:    So, "env - foo" will invoke the "foo" program in a null environment,
        !            32:    whereas "env foo" would invoke "foo" in the same environment as that
        !            33:    passed to "env" itself.
        !            34: 
        !            35:    Subsequent arguments are interpreted as follows:
        !            36:    
        !            37:    * "variable=value" (ie an arg containing a "=" character)
        !            38:      means to set the specified environment variable to that value.
        !            39:      `value' may be of zero length ("variable=").  Note that setting
        !            40:      a variable to a zero-length value is different from unsetting it.
        !            41: 
        !            42:    * "-u variable" or "-unset variable"
        !            43:      means to unset that variable
        !            44:      If that variable isn't set, does nothing.
        !            45: 
        !            46:    * "-s variable value" or "-set variable value"
        !            47:      same as "variable=value"
        !            48: 
        !            49:    * "-" or "--"
        !            50:      are used to indicate that the following argument is the program
        !            51:      to invoke.  This is only necessary when the program's name
        !            52:      begins with "-" or contains a "="
        !            53: 
        !            54:    * anything else
        !            55:      The first remaining argument specifies a program to invoke
        !            56:      (it is searched for according to the specification of the PATH
        !            57:      environment variable) and any arguments following that are
        !            58:      passed as arguments to that program
        !            59: 
        !            60:      If no program-name is specified following the environment
        !            61:      specifications the the resulting environment is printed
        !            62:      (The is like specifying a program-name of "printenv")
        !            63: 
        !            64:    Examples:
        !            65:      If the environment passed to "env" is
        !            66:      { USER=rms EDITOR=emacs PATH=.:/gnubin:/hacks }
        !            67: 
        !            68:      * "env DISPLAY=gnu:0 nemacs"
        !            69:         calls "nemacs" in the envionment
        !            70:        { EDITOR=emacs USER=rms DISPLAY=gnu }
        !            71: 
        !            72:      * "env - USER=foo /hacks/hack bar baz"
        !            73:        will call the "hack" program on arguments "bar" and "baz"
        !            74:        in an environment in which the only variable is "USER"
        !            75:        Note that the "-" option will clear out the PATH variable,
        !            76:        so one should be careful to specify in which directory
        !            77:        to find the program to call
        !            78:        
        !            79:      * "env -u EDITOR USER=foo PATH=/energy -- e=mc2 bar baz"
        !            80:        The program "/energy/e=mc2" is called with environment
        !            81:        { USER=foo PATH=/energy }
        !            82: 
        !            83: */
        !            84: 
        !            85: #ifdef EMACS
        !            86: #define NO_SHORTNAMES
        !            87: #include "../src/config.h"
        !            88: #endif /* EMACS */
        !            89: 
        !            90: #include <stdio.h>
        !            91: #include <errno.h>
        !            92: 
        !            93: extern int execvp ();
        !            94: extern char *index ();
        !            95: 
        !            96: char *xmalloc (), *xrealloc ();
        !            97: char *concat ();
        !            98: 
        !            99: extern char **environ;
        !           100: 
        !           101: char **nenv;
        !           102: int nenv_size;
        !           103: 
        !           104: char *progname;
        !           105: void setenv ();
        !           106: void fatal ();
        !           107: 
        !           108: main (argc, argv, envp)
        !           109:      register int argc;
        !           110:      register char **argv;
        !           111:      char **envp;
        !           112: {
        !           113:   register char *tem;
        !           114: 
        !           115:   progname = argv[0];
        !           116:   argc--;
        !           117:   argv++;
        !           118: 
        !           119:   nenv_size = 100;
        !           120:   nenv = (char **) xmalloc (nenv_size * sizeof (char *));
        !           121:   *nenv = (char *) 0;
        !           122: 
        !           123:   /* "-" flag means to not inherit parent's environment */
        !           124:   if (argc && !strcmp (*argv, "-"))
        !           125:     {
        !           126:       argc--;
        !           127:       argv++;
        !           128:     }
        !           129:   else
        !           130:     /* Else pass on existing env vars. */
        !           131:     for (; *envp; envp++)
        !           132:       {
        !           133:        tem = index (*envp, '=');
        !           134:        if (tem)
        !           135:          {
        !           136:            *tem = '\000';
        !           137:            setenv (*envp, tem + 1);
        !           138:          }
        !           139:      }
        !           140: 
        !           141:   while (argc > 0)
        !           142:     {
        !           143:       tem = index (*argv, '=');
        !           144:       if (tem)
        !           145:        /* If arg contains a "=" it specifies to set a variable */
        !           146:        {
        !           147:          *tem = '\000';
        !           148:          setenv (*argv, tem + 1);
        !           149:          argc--; argv++;
        !           150:          continue;
        !           151:        }
        !           152:       
        !           153:       if (**argv != '-')
        !           154:        /* Remaining args are program name and args to pass it */
        !           155:        break;
        !           156: 
        !           157:       if (argc < 2)
        !           158:        fatal ("No argument following \"%s\" switch", *argv);
        !           159:        if (!strcmp (*argv, "-u") ||
        !           160:               !strcmp (*argv, "-unset"))
        !           161:        /* Unset a variable */
        !           162:        {
        !           163:          argc--; argv++;
        !           164:          setenv (*argv, 0);
        !           165:          argc--; argv++;
        !           166:        }
        !           167:       else if (!strcmp (*argv, "-s") ||
        !           168:               !strcmp (*argv, "-set"))
        !           169:        /* Set a variable */
        !           170:        {
        !           171:          argc--; argv++;
        !           172:          tem = *argv;
        !           173:          if (argc < 2)
        !           174:            fatal ("No value specified for variable \"%s\"",
        !           175:                   tem);
        !           176:          argc--; argv++;
        !           177:          setenv (tem, *argv);
        !           178:          argc--; argv++;
        !           179:        }
        !           180:       else if (!strcmp (*argv, "-") || !strcmp (*argv, "--"))
        !           181:        {
        !           182:          argc--; argv++;
        !           183:          break;
        !           184:        }
        !           185:       else
        !           186:        {
        !           187:          fatal ("unknown switch \"%s\"", *argv);
        !           188:        }
        !           189:     }
        !           190: 
        !           191:   /* If no program specified print the environment and exit */
        !           192:   if (argc <= 0)
        !           193:     {
        !           194:       while (*nenv)
        !           195:        printf ("%s\n", *nenv++);
        !           196:       exit (0);
        !           197:     }
        !           198:   else
        !           199:     {
        !           200:       extern int errno, sys_nerr;
        !           201:       extern char *sys_errlist[];
        !           202: 
        !           203:       environ = nenv;
        !           204:       (void) execvp (*argv, argv);
        !           205: 
        !           206:       fprintf (stderr, "%s: Cannot execute \"%s\"",
        !           207:               progname, *argv);
        !           208:       if (errno < sys_nerr)
        !           209:        fprintf (stderr, ": %s\n" , sys_errlist[errno]);
        !           210:       else
        !           211:        putc ('\n', stderr);
        !           212:       exit (errno != 0 ? errno : 1);
        !           213:     }
        !           214: }
        !           215: 
        !           216: void
        !           217: setenv (var, val)
        !           218:   register char *var, *val;
        !           219: {
        !           220:   register char **e;
        !           221:   int len = strlen (var);
        !           222: 
        !           223:   {
        !           224:     register char *tem = index (var, '=');
        !           225:     if (tem)
        !           226:       fatal ("Environment variable names may not contain \"=\": %s",
        !           227:             var);
        !           228:     else if (*var == '\000')
        !           229:       fatal ("Zero-length environment variable name specified.");
        !           230:   }
        !           231: 
        !           232:   for (e = nenv; *e; e++)
        !           233:     if (!strncmp (var, *e, len) &&
        !           234:        (*e)[len] == '=')
        !           235:       {
        !           236:        if (val)
        !           237:          goto set;
        !           238:        else
        !           239:          do { *e = *(e + 1); } while (*e++);
        !           240:        return;
        !           241:       }
        !           242: 
        !           243:   if (!val)
        !           244:     return; /* Nothing to unset */
        !           245: 
        !           246:   len = e - nenv;
        !           247:   if (len + 1 >= nenv_size)
        !           248:     {
        !           249:       nenv_size += 100;
        !           250:       nenv = (char **) xrealloc (nenv, nenv_size * sizeof (char *));
        !           251:       e = nenv + len;
        !           252:     }
        !           253: 
        !           254:  set:
        !           255:   val = concat (var, "=", val);
        !           256:   if (*e)
        !           257:     free (*e);
        !           258:   else
        !           259:     *(e + 1) = (char *) 0;
        !           260:   *e = val;
        !           261:   return;
        !           262: }
        !           263: 
        !           264: void
        !           265: fatal (msg, arg1, arg2)
        !           266:      char *msg, *arg1, *arg2;
        !           267: {
        !           268:   fprintf (stderr, "%s: ", progname);
        !           269:   fprintf (stderr, msg, arg1, arg2);
        !           270:   putc ('\n', stderr);
        !           271:   exit (1);
        !           272: }
        !           273: 
        !           274: 
        !           275: extern char *malloc (), *realloc ();
        !           276: 
        !           277: void
        !           278: memory_fatal ()
        !           279: {
        !           280:   fatal ("Out of memory");
        !           281: }
        !           282: 
        !           283: char *
        !           284: xmalloc (size)
        !           285:      int size;
        !           286: {
        !           287:   register char *value;
        !           288:   value = (char *) malloc (size);
        !           289:   if (!value) memory_fatal ();
        !           290:   return (value);
        !           291: }
        !           292: 
        !           293: char *
        !           294: xrealloc (ptr, size)
        !           295:      char *ptr;
        !           296:      int size;
        !           297: {
        !           298:   register char *value;
        !           299:   value = (char *) realloc (ptr, size);
        !           300:   if (!value) memory_fatal ();
        !           301:   return (value);
        !           302: }
        !           303: 
        !           304: /* Return a newly-allocated string whose contents concatenate those of s1, s2, s3.  */
        !           305: 
        !           306: char *
        !           307: concat (s1, s2, s3)
        !           308:      char *s1, *s2, *s3;
        !           309: {
        !           310:   int len1 = strlen (s1), len2 = strlen (s2), len3 = strlen (s3);
        !           311:   char *result = (char *) xmalloc (len1 + len2 + len3 + 1);
        !           312: 
        !           313:   strcpy (result, s1);
        !           314:   strcpy (result + len1, s2);
        !           315:   strcpy (result + len1 + len2, s3);
        !           316:   *(result + len1 + len2 + len3) = 0;
        !           317: 
        !           318:   return result;
        !           319: }
        !           320: 
        !           321: 
        !           322: /*
        !           323:  * Local variables:
        !           324:  * compile-command: "cc -g -o env env.c"
        !           325:  * end:
        !           326:  */

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