chown.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 <errno.h>
  17 #include <string.h>
  18
  19 #include <pwd.h>
  20 #include <grp.h>
  21 #include <unistd.h>
  22
  23 #define VERSION "0.01"
  24
  25 int main(int argc, char* argv[])
  26 {
  27     if (argc == 1) {
  28         fprintf(stderr, "%s: missing operand\n"
  29                         "Run '%s --help' for usage.\n",
  30                         argv[0], argv[0]);
  31         return 1;
  32     }
  33
  34     // flag parsing
  35     int arg = 0;
  36     for (arg = 1; arg < argc; arg++)
  37     {
  38         if (strcmp(argv[arg], "--help") == 0) {
  39             printf("Usage: %s [owner][:group] [file ...]\n", argv[0]);
  40             return 0;
  41         } else if (strcmp(argv[arg], "--version") == 0) {
  42             printf("chown (mutos) v"VERSION"\n");
  43             return 0;
  44         } else {
  45             break;
  46         }
  47     }
  48
  49     int colon_index = -1;
  50     for (size_t i = 0; i < strlen(argv[arg]); i++)
  51     {
  52         if (argv[arg][i] == ':') {
  53             colon_index = i;
  54             break;
  55         }
  56     }
  57
  58     struct passwd *user  = NULL;
  59     struct group  *group = NULL;
  60
  61     char* username  = NULL;
  62     char* groupname = NULL;
  63
  64     if (colon_index == -1) {
  65         user = getpwnam(argv[arg]);
  66         username  = argv[arg];
  67     } else {
  68         username  = strndup(argv[arg], colon_index);
  69         groupname = strndup(argv[arg] + colon_index + 1, strlen(argv[arg] - colon_index - 1));
  70
  71         user = getpwnam(username);
  72         group = getgrnam(groupname);
  73     }
  74
  75     if (!user) {
  76         fprintf(stderr, "%s: invalid user: '%s'\n",
  77                          argv[0],           username);
  78         return 1;
  79     }
  80
  81     if (!group && groupname) {
  82         fprintf(stderr, "%s: invalid group: '%s'\n",
  83                          argv[0],           groupname);
  84         return 1;
  85     }
  86
  87     arg++; // go to next arg
  88
  89     if (argc - arg < 1) {
  90         fprintf(stderr, "%s: No file specified\n", argv[0]);
  91         return 1;
  92     }
  93
  94     for ( ; arg < argc; arg++)
  95     {
  96         int rc = chown(argv[arg], user->pw_uid, group ? group->gr_gid : (gid_t) -1);
  97         if (rc == -1) {
  98             fprintf(stderr, "%s: %s: %s\n", argv[0], strerror(errno), argv[arg]);
  99             return 1;
 100         }
 101     }
 102
 103     return 0;
 104 }