env.c

   1 /*
   2     Copyright © 2013 Alastair Stuart
   3
   4     This program is open source software: you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation, either version 3 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  12     GNU General Public License for more details.
  13 */
  14
  15 #include <stdio.h>
  16 #include <string.h>
  17 #include <stdlib.h>
  18 #include <errno.h>
  19
  20 #include <unistd.h>
  21
  22 #define VERSION "0.01"
  23
  24 extern char **environ;
  25
  26 int main(int argc, char* argv[])
  27 {
  28     // flag parsing
  29     int arg = 0;
  30     for (arg = 1; arg < argc; arg++)
  31     {
  32         if (strcmp("--help", argv[arg]) == 0 || strcmp("-h", argv[arg]) == 0) {
  33             printf("Usage: %s [name=value ...] [command]\n", argv[0]);
  34             printf("\n"
  35                    "If no command is given, all environment variables are listed.\n"
  36                    "\n"
  37                    "    --help              Print this message.\n"
  38                    "    --version           Show version info.\n");
  39             return 0;
  40         } else if (strcmp("--version", argv[arg]) == 0 || strcmp("-v", argv[arg]) == 0) {
  41             printf("env (mutos) v"VERSION"\n");
  42             return 0;
  43         } else {
  44             // no more flags
  45             break;
  46         }
  47     }
  48
  49     // parse the key-value pairs
  50     for ( ; arg < argc; arg++)
  51     {
  52         // find the equals
  53         char* equals = strchr(argv[arg], '=');
  54         // if there's no equals, it must be a command
  55         if (!equals) {
  56             break;
  57         }
  58         // delete it
  59         *equals = '\0';
  60         char* name  = argv[arg];
  61         // the value string starts right after the equals
  62         char* value = equals + 1;
  63         setenv(name, value, 1);
  64     }
  65
  66     // parse command
  67     size_t total_len = 0;
  68     for (int i = arg; i < argc; i++)
  69     {
  70         total_len += strlen(argv[i]) + 1;
  71     }
  72
  73     char* command = NULL;
  74     if (arg < argc) {
  75         command = calloc(total_len, sizeof(char));
  76     }
  77
  78     for (int i = arg; i < argc; i++)
  79     {
  80         strcat(command, argv[i]);
  81         if (i != argc - 1) {
  82             strcat(command, " ");
  83         }
  84     }
  85
  86     if (arg < argc) {
  87         command[total_len - 1] = '\0';
  88     }
  89
  90     if (command) {
  91         system(command);
  92     } else {
  93         for (char **env = environ; *env; ++env)
  94         {
  95             printf("%s\n", *env);
  96         }
  97     }
  98
  99     return 0;
 100 }