diplodocus.org Git - nmh/blob - docs/historical/mh-jun-1982/subs/putenv.c

   1 #ifdef COMMENT
   2         Proprietary Rand Corporation, 1981.
   3         Further distribution of this software
   4         subject to the terms of the Rand
   5         license agreement.
   6 #endif
   7
   8 /*
   9  *      putenv(name, arg)
  10  *      replaces or adds the `name' entry with "name=arg";
  11  *
  12  *      Uses malloc() for space for new vector and new entry;
  13  *
  14  *      Bruce Borden            January 1980
  15  *      The Rand Corporation
  16  */
  17
  18 #include <stdio.h>
  19
  20 extern  char **environ;
  21
  22 putenv(name, arg)
  23 char *name, *arg;
  24 {
  25         register int i;
  26         register char **ep, **nep, *cp;
  27
  28         if((cp = (char *) malloc(strlen(name) + strlen(arg) + 2)) == NULL)
  29                 return(1);
  30         strcpy(cp, name);
  31         strcat(cp, "=");
  32         strcat(cp, arg);
  33         for(ep = environ, i = 0; *ep; ep++, i++)
  34                 if(nvmatch(name, *ep)) {
  35                         *ep = cp;
  36                         return(0);
  37                 }
  38         if((nep = (char **) malloc((i+2) * sizeof *nep)) == NULL)
  39                 return(1);
  40         for(ep = environ, i = 0; *ep; )
  41                 nep[i++] = *ep++;
  42         nep[i++] = cp;
  43         nep[i] = 0;
  44         environ = nep;
  45         return(0);
  46 }
  47
  48 /*
  49  *      s1 is either name, or name=value
  50  *      s2 is name=value
  51  *      if names match, return value of s2, else NULL
  52  *      used for environment searching: see getenv
  53  */
  54
  55 static
  56 nvmatch(s1, s2)
  57 register char *s1, *s2;
  58 {
  59
  60         while (*s1 == *s2++)
  61                 if (*s1++ == '=')
  62                         return(1);
  63         if (*s1 == '\0' && *(s2-1) == '=')
  64                 return(1);
  65         return(0);
  66 }