src/echo.c

   1 /* echo.c, derived from code echo.c in Bash.
   2    Copyright (C) 87,89, 1991-1997, 1999-2005, 2007-2009 Free Software
   3    Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation, either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19 #include <stdio.h>
  20 #include <sys/types.h>
  21 #include "system.h"
  22
  23 /* The official name of this program (e.g., no `g' prefix).  */
  24 #define PROGRAM_NAME "echo"
  25
  26 #define AUTHORS \
  27   proper_name ("Brian Fox"), \
  28   proper_name ("Chet Ramey")
  29
  30 /* If true, interpret backslash escapes by default.  */
  31 #ifndef DEFAULT_ECHO_TO_XPG
  32 enum { DEFAULT_ECHO_TO_XPG = false };
  33 #endif
  34
  35 void
  36 usage (int status)
  37 {
  38   if (status != EXIT_SUCCESS)
  39     fprintf (stderr, _("Try `%s --help' for more information.\n"),
  40              program_name);
  41   else
  42     {
  43       printf (_("\
  44 Usage: %s [SHORT-OPTION]... [STRING]...\n\
  45   or:  %s LONG-OPTION\n\
  46 "), program_name, program_name);
  47       fputs (_("\
  48 Echo the STRING(s) to standard output.\n\
  49 \n\
  50   -n             do not output the trailing newline\n\
  51 "), stdout);
  52       fputs (_(DEFAULT_ECHO_TO_XPG
  53                ? N_("\
  54   -e             enable interpretation of backslash escapes (default)\n\
  55   -E             disable interpretation of backslash escapes\n")
  56                : N_("\
  57   -e             enable interpretation of backslash escapes\n\
  58   -E             disable interpretation of backslash escapes (default)\n")),
  59              stdout);
  60       fputs (HELP_OPTION_DESCRIPTION, stdout);
  61       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  62       fputs (_("\
  63 \n\
  64 If -e is in effect, the following sequences are recognized:\n\
  65 \n\
  66   \\0NNN   the character whose ASCII code is NNN (octal)\n\
  67   \\\\     backslash\n\
  68   \\a     alert (BEL)\n\
  69   \\b     backspace\n\
  70 "), stdout);
  71       fputs (_("\
  72   \\c     produce no further output\n\
  73   \\f     form feed\n\
  74   \\n     new line\n\
  75   \\r     carriage return\n\
  76   \\t     horizontal tab\n\
  77   \\v     vertical tab\n\
  78 "), stdout);
  79       printf (USAGE_BUILTIN_WARNING, PROGRAM_NAME);
  80       emit_bug_reporting_address ();
  81     }
  82   exit (status);
  83 }
  84
  85 /* Convert C from hexadecimal character to integer.  */
  86 static int
  87 hextobin (unsigned char c)
  88 {
  89   switch (c)
  90     {
  91     default: return c - '0';
  92     case 'a': case 'A': return 10;
  93     case 'b': case 'B': return 11;
  94     case 'c': case 'C': return 12;
  95     case 'd': case 'D': return 13;
  96     case 'e': case 'E': return 14;
  97     case 'f': case 'F': return 15;
  98     }
  99 }
 100
 101 /* Print the words in LIST to standard output.  If the first word is
 102    `-n', then don't print a trailing newline.  We also support the
 103    echo syntax from Version 9 unix systems. */
 104
 105 int
 106 main (int argc, char **argv)
 107 {
 108   bool display_return = true;
 109   bool allow_options =
 110     (! getenv ("POSIXLY_CORRECT")
 111      || (! DEFAULT_ECHO_TO_XPG && 1 < argc && STREQ (argv[1], "-n")));
 112
 113   /* System V machines already have a /bin/sh with a v9 behavior.
 114      Use the identical behavior for these machines so that the
 115      existing system shell scripts won't barf.  */
 116   bool do_v9 = DEFAULT_ECHO_TO_XPG;
 117
 118   initialize_main (&argc, &argv);
 119   set_program_name (argv[0]);
 120   setlocale (LC_ALL, "");
 121   bindtextdomain (PACKAGE, LOCALEDIR);
 122   textdomain (PACKAGE);
 123
 124   atexit (close_stdout);
 125
 126   /* We directly parse options, rather than use parse_long_options, in
 127      order to avoid accepting abbreviations.  */
 128   if (allow_options && argc == 2)
 129     {
 130       if (STREQ (argv[1], "--help"))
 131         usage (EXIT_SUCCESS);
 132
 133       if (STREQ (argv[1], "--version"))
 134         {
 135           version_etc (stdout, PROGRAM_NAME, PACKAGE_NAME, Version, AUTHORS,
 136                        (char *) NULL);
 137           exit (EXIT_SUCCESS);
 138         }
 139     }
 140
 141   --argc;
 142   ++argv;
 143
 144   if (allow_options)
 145     while (argc > 0 && *argv[0] == '-')
 146       {
 147         char const *temp = argv[0] + 1;
 148         size_t i;
 149
 150         /* If it appears that we are handling options, then make sure that
 151            all of the options specified are actually valid.  Otherwise, the
 152            string should just be echoed.  */
 153
 154         for (i = 0; temp[i]; i++)
 155           switch (temp[i])
 156             {
 157             case 'e': case 'E': case 'n':
 158               break;
 159             default:
 160               goto just_echo;
 161             }
 162
 163         if (i == 0)
 164           goto just_echo;
 165
 166         /* All of the options in TEMP are valid options to ECHO.
 167            Handle them. */
 168         while (*temp)
 169           switch (*temp++)
 170             {
 171             case 'e':
 172               do_v9 = true;
 173               break;
 174
 175             case 'E':
 176               do_v9 = false;
 177               break;
 178
 179             case 'n':
 180               display_return = false;
 181               break;
 182             }
 183
 184         argc--;
 185         argv++;
 186       }
 187
 188 just_echo:
 189
 190   if (do_v9)
 191     {
 192       while (argc > 0)
 193         {
 194           char const *s = argv[0];
 195           unsigned char c;
 196
 197           while ((c = *s++))
 198             {
 199               if (c == '\\' && *s)
 200                 {
 201                   switch (c = *s++)
 202                     {
 203                     case 'a': c = '\a'; break;
 204                     case 'b': c = '\b'; break;
 205                     case 'c': exit (EXIT_SUCCESS);
 206                     case 'f': c = '\f'; break;
 207                     case 'n': c = '\n'; break;
 208                     case 'r': c = '\r'; break;
 209                     case 't': c = '\t'; break;
 210                     case 'v': c = '\v'; break;
 211                     case 'x':
 212                       {
 213                         unsigned char ch = *s;
 214                         if (! isxdigit (ch))
 215                           goto not_an_escape;
 216                         s++;
 217                         c = hextobin (ch);
 218                         ch = *s;
 219                         if (isxdigit (ch))
 220                           {
 221                             s++;
 222                             c = c * 16 + hextobin (ch);
 223                           }
 224                       }
 225                       break;
 226                     case '0':
 227                       c = 0;
 228                       if (! ('0' <= *s && *s <= '7'))
 229                         break;
 230                       c = *s++;
 231                       /* Fall through.  */
 232                     case '1': case '2': case '3':
 233                     case '4': case '5': case '6': case '7':
 234                       c -= '0';
 235                       if ('0' <= *s && *s <= '7')
 236                         c = c * 8 + (*s++ - '0');
 237                       if ('0' <= *s && *s <= '7')
 238                         c = c * 8 + (*s++ - '0');
 239                       break;
 240                     case '\\': break;
 241
 242                     not_an_escape:
 243                     default:  putchar ('\\'); break;
 244                     }
 245                 }
 246               putchar (c);
 247             }
 248           argc--;
 249           argv++;
 250           if (argc > 0)
 251             putchar (' ');
 252         }
 253     }
 254   else
 255     {
 256       while (argc > 0)
 257         {
 258           fputs (argv[0], stdout);
 259           argc--;
 260           argv++;
 261           if (argc > 0)
 262             putchar (' ');
 263         }
 264     }
 265
 266   if (display_return)
 267     putchar ('\n');
 268   exit (EXIT_SUCCESS);
 269 }