contrib/tcp_wrappers/environ.c

   1 /*
   2  * Many systems have putenv() but no setenv(). Other systems have setenv()
   3  * but no putenv() (MIPS). Still other systems have neither (NeXT). This is a
   4  * re-implementation that hopefully ends all problems.
   5  *
   6  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
   7  */
   8
   9 #ifndef lint
  10 static char sccsid[] = "@(#) environ.c 1.2 94/03/23 16:09:46";
  11 #endif
  12
  13 /* System libraries. */
  14
  15 extern char **environ;
  16 extern char *strchr();
  17 extern char *strcpy();
  18 extern char *strncpy();
  19 extern char *malloc();
  20 extern char *realloc();
  21 extern int strncmp();
  22 extern void free();
  23
  24 #ifdef no_memcpy
  25 #define memcpy(d,s,l) bcopy(s,d,l)
  26 #else
  27 extern char *memcpy();
  28 #endif
  29
  30 /* Local stuff. */
  31
  32 static int addenv();                    /* append entry to environment */
  33
  34 static int allocated = 0;               /* environ is, or is not, allocated */
  35
  36 #define DO_CLOBBER      1
  37
  38 /* namelength - determine length of name in "name=whatever" */
  39
  40 static int namelength(name)
  41 char   *name;
  42 {
  43     char   *equal;
  44
  45     equal = strchr(name, '=');
  46     return ((equal == 0) ? strlen(name) : (equal - name));
  47 }
  48
  49 /* findenv - given name, locate name=value */
  50
  51 static char **findenv(name, len)
  52 char   *name;
  53 int     len;
  54 {
  55     char  **envp;
  56
  57     for (envp = environ; envp && *envp; envp++)
  58         if (strncmp(name, *envp, len) == 0 && (*envp)[len] == '=')
  59             return (envp);
  60     return (0);
  61 }
  62
  63 /* getenv - given name, locate value */
  64
  65 char   *getenv(name)
  66 char   *name;
  67 {
  68     int     len = namelength(name);
  69     char  **envp = findenv(name, len);
  70
  71     return (envp ? *envp + len + 1 : 0);
  72 }
  73
  74 /* putenv - update or append environment (name,value) pair */
  75
  76 int     putenv(nameval)
  77 char   *nameval;
  78 {
  79     char   *equal = strchr(nameval, '=');
  80     char   *value = (equal ? equal : "");
  81
  82     return (setenv(nameval, value, DO_CLOBBER));
  83 }
  84
  85 /* unsetenv - remove variable from environment */
  86
  87 void    unsetenv(name)
  88 char   *name;
  89 {
  90     char  **envp;
  91
  92     if ((envp = findenv(name, namelength(name))) != 0)
  93         while (envp[0] = envp[1])
  94             envp++;
  95 }
  96
  97 /* setenv - update or append environment (name,value) pair */
  98
  99 int     setenv(name, value, clobber)
 100 char   *name;
 101 char   *value;
 102 int     clobber;
 103 {
 104     char   *destination;
 105     char  **envp;
 106     int     l_name;                     /* length of name part */
 107     int     l_nameval;                  /* length of name=value */
 108
 109     /* Permit name= and =value. */
 110
 111     l_name = namelength(name);
 112     envp = findenv(name, l_name);
 113     if (envp != 0 && clobber == 0)
 114         return (0);
 115     if (*value == '=')
 116         value++;
 117     l_nameval = l_name + strlen(value) + 1;
 118
 119     /*
 120      * Use available memory if the old value is long enough. Never free an
 121      * old name=value entry because it may not be allocated.
 122      */
 123
 124     destination = (envp != 0 && strlen(*envp) >= l_nameval) ?
 125         *envp : malloc(l_nameval + 1);
 126     if (destination == 0)
 127         return (-1);
 128     strncpy(destination, name, l_name);
 129     destination[l_name] = '=';
 130     strcpy(destination + l_name + 1, value);
 131     return ((envp == 0) ? addenv(destination) : (*envp = destination, 0));
 132 }
 133
 134 /* cmalloc - malloc and copy block of memory */
 135
 136 static char *cmalloc(new_len, old, old_len)
 137 char   *old;
 138 int     old_len;
 139 {
 140     char   *new = malloc(new_len);
 141
 142     if (new != 0)
 143         memcpy(new, old, old_len);
 144     return (new);
 145 }
 146
 147 /* addenv - append environment entry */
 148
 149 static int addenv(nameval)
 150 char   *nameval;
 151 {
 152     char  **envp;
 153     int     n_used;                     /* number of environment entries */
 154     int     l_used;                     /* bytes used excl. terminator */
 155     int     l_need;                     /* bytes needed incl. terminator */
 156
 157     for (envp = environ; envp && *envp; envp++)
 158          /* void */ ;
 159     n_used = envp - environ;
 160     l_used = n_used * sizeof(*envp);
 161     l_need = l_used + 2 * sizeof(*envp);
 162
 163     envp = allocated ?
 164         (char **) realloc((char *) environ, l_need) :
 165         (char **) cmalloc(l_need, (char *) environ, l_used);
 166     if (envp == 0) {
 167         return (-1);
 168     } else {
 169         allocated = 1;
 170         environ = envp;
 171         environ[n_used++] = nameval;            /* add new entry */
 172         environ[n_used] = 0;                    /* terminate list */
 173         return (0);
 174     }
 175 }
 176
 177 #ifdef TEST
 178
 179  /*
 180   * Stand-alone program for test purposes.
 181   */
 182
 183 /* printenv - display environment */
 184
 185 static void printenv()
 186 {
 187     char  **envp;
 188
 189     for (envp = environ; envp && *envp; envp++)
 190         printf("%s\n", *envp);
 191 }
 192
 193 int     main(argc, argv)
 194 int     argc;
 195 char  **argv;
 196 {
 197     char   *cp;
 198     int     changed = 0;
 199
 200     if (argc < 2) {
 201         printf("usage: %s name[=value]...\n", argv[0]);
 202         return (1);
 203     }
 204     while (--argc && *++argv) {
 205         if (argv[0][0] == '-') {                /* unsetenv() test */
 206             unsetenv(argv[0] + 1);
 207             changed = 1;
 208         } else if (strchr(argv[0], '=') == 0) { /* getenv() test */
 209             cp = getenv(argv[0]);
 210             printf("%s: %s\n", argv[0], cp ? cp : "not found");
 211         } else {                                /* putenv() test */
 212             if (putenv(argv[0])) {
 213                 perror("putenv");
 214                 return (1);
 215             }
 216             changed = 1;
 217         }
 218     }
 219     if (changed)
 220         printenv();
 221     return (0);
 222 }
 223
 224 #endif /* TEST */