src/printenv.c

   1 /* printenv -- print all or part of environment
   2    Copyright (C) 1989-2024 Free Software Foundation, Inc.
   3
   4    This program is free 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    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Usage: printenv [variable...]
  18
  19    If no arguments are given, print the entire environment.
  20    If one or more variable names are given, print the value of
  21    each one that is set, and nothing for ones that are not set.
  22
  23    Exit status:
  24    0 if all variables specified were found
  25    1 if not
  26    2 if some other error occurred
  27
  28    David MacKenzie and Richard Mlynarik */
  29
  30 #include <config.h>
  31 #include <stdio.h>
  32 #include <sys/types.h>
  33 #include <getopt.h>
  34
  35 #include "system.h"
  36
  37 /* Exit status for syntax errors, etc.  */
  38 enum { PRINTENV_FAILURE = 2 };
  39
  40 /* The official name of this program (e.g., no 'g' prefix).  */
  41 #define PROGRAM_NAME "printenv"
  42
  43 #define AUTHORS \
  44   proper_name ("David MacKenzie"), \
  45   proper_name ("Richard Mlynarik")
  46
  47 static struct option const longopts[] =
  48 {
  49   {"null", no_argument, nullptr, '0'},
  50   {GETOPT_HELP_OPTION_DECL},
  51   {GETOPT_VERSION_OPTION_DECL},
  52   {nullptr, 0, nullptr, 0}
  53 };
  54
  55 void
  56 usage (int status)
  57 {
  58   if (status != EXIT_SUCCESS)
  59     emit_try_help ();
  60   else
  61     {
  62       printf (_("\
  63 Usage: %s [OPTION]... [VARIABLE]...\n\
  64 Print the values of the specified environment VARIABLE(s).\n\
  65 If no VARIABLE is specified, print name and value pairs for them all.\n\
  66 \n\
  67 "),
  68               program_name);
  69       fputs (_("\
  70   -0, --null     end each output line with NUL, not newline\n\
  71 "), stdout);
  72       fputs (HELP_OPTION_DESCRIPTION, stdout);
  73       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  74       printf (USAGE_BUILTIN_WARNING, PROGRAM_NAME);
  75       emit_ancillary_info (PROGRAM_NAME);
  76     }
  77   exit (status);
  78 }
  79
  80 int
  81 main (int argc, char **argv)
  82 {
  83   char **env;
  84   char *ep, *ap;
  85   int i;
  86   bool ok;
  87   int optc;
  88   bool opt_nul_terminate_output = false;
  89
  90   initialize_main (&argc, &argv);
  91   set_program_name (argv[0]);
  92   setlocale (LC_ALL, "");
  93   bindtextdomain (PACKAGE, LOCALEDIR);
  94   textdomain (PACKAGE);
  95
  96   initialize_exit_failure (PRINTENV_FAILURE);
  97   atexit (close_stdout);
  98
  99   while ((optc = getopt_long (argc, argv, "+iu:0", longopts, nullptr)) != -1)
 100     {
 101       switch (optc)
 102         {
 103         case '0':
 104           opt_nul_terminate_output = true;
 105           break;
 106         case_GETOPT_HELP_CHAR;
 107         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 108         default:
 109           usage (PRINTENV_FAILURE);
 110         }
 111     }
 112
 113   if (optind >= argc)
 114     {
 115       for (env = environ; *env != nullptr; ++env)
 116         printf ("%s%c", *env, opt_nul_terminate_output ? '\0' : '\n');
 117       ok = true;
 118     }
 119   else
 120     {
 121       int matches = 0;
 122
 123       for (i = optind; i < argc; ++i)
 124         {
 125           bool matched = false;
 126
 127           /* 'printenv a=b' is silent, even if 'a=b=c' is in environ.  */
 128           if (strchr (argv[i], '='))
 129             continue;
 130
 131           for (env = environ; *env; ++env)
 132             {
 133               ep = *env;
 134               ap = argv[i];
 135               while (*ep != '\0' && *ap != '\0' && *ep++ == *ap++)
 136                 {
 137                   if (*ep == '=' && *ap == '\0')
 138                     {
 139                       printf ("%s%c", ep + 1,
 140                               opt_nul_terminate_output ? '\0' : '\n');
 141                       matched = true;
 142                       break;
 143                     }
 144                 }
 145             }
 146
 147           matches += matched;
 148         }
 149
 150       ok = (matches == argc - optind);
 151     }
 152
 153   return ok ? EXIT_SUCCESS : EXIT_FAILURE;
 154 }