src/echo.c

   1 /* echo.c, derived from code echo.c in Bash.
   2    Copyright (C) 1987, 1989, 1991-1997, 1999-2005, 2007-2010 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 "), stdout);
  67       fputs (_("\
  68   \\\\      backslash\n\
  69   \\a      alert (BEL)\n\
  70   \\b      backspace\n\
  71   \\c      produce no further output\n\
  72   \\e      escape\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       fputs (_("\
  80   \\0NNN   byte with octal value NNN (1 to 3 digits)\n\
  81   \\xHH    byte with hexadecimal value HH (1 to 2 digits)\n\
  82 "), stdout);
  83       printf (USAGE_BUILTIN_WARNING, PROGRAM_NAME);
  84       emit_ancillary_info ();
  85     }
  86   exit (status);
  87 }
  88
  89 /* Convert C from hexadecimal character to integer.  */
  90 static int
  91 hextobin (unsigned char c)
  92 {
  93   switch (c)
  94     {
  95     default: return c - '0';
  96     case 'a': case 'A': return 10;
  97     case 'b': case 'B': return 11;
  98     case 'c': case 'C': return 12;
  99     case 'd': case 'D': return 13;
 100     case 'e': case 'E': return 14;
 101     case 'f': case 'F': return 15;
 102     }
 103 }
 104
 105 /* Print the words in LIST to standard output.  If the first word is
 106    `-n', then don't print a trailing newline.  We also support the
 107    echo syntax from Version 9 unix systems. */
 108
 109 int
 110 main (int argc, char **argv)
 111 {
 112   bool display_return = true;
 113   bool allow_options =
 114     (! getenv ("POSIXLY_CORRECT")
 115      || (! DEFAULT_ECHO_TO_XPG && 1 < argc && STREQ (argv[1], "-n")));
 116
 117   /* System V machines already have a /bin/sh with a v9 behavior.
 118      Use the identical behavior for these machines so that the
 119      existing system shell scripts won't barf.  */
 120   bool do_v9 = DEFAULT_ECHO_TO_XPG;
 121
 122   initialize_main (&argc, &argv);
 123   set_program_name (argv[0]);
 124   setlocale (LC_ALL, "");
 125   bindtextdomain (PACKAGE, LOCALEDIR);
 126   textdomain (PACKAGE);
 127
 128   atexit (close_stdout);
 129
 130   /* We directly parse options, rather than use parse_long_options, in
 131      order to avoid accepting abbreviations.  */
 132   if (allow_options && argc == 2)
 133     {
 134       if (STREQ (argv[1], "--help"))
 135         usage (EXIT_SUCCESS);
 136
 137       if (STREQ (argv[1], "--version"))
 138         {
 139           version_etc (stdout, PROGRAM_NAME, PACKAGE_NAME, Version, AUTHORS,
 140                        (char *) NULL);
 141           exit (EXIT_SUCCESS);
 142         }
 143     }
 144
 145   --argc;
 146   ++argv;
 147
 148   if (allow_options)
 149     while (argc > 0 && *argv[0] == '-')
 150       {
 151         char const *temp = argv[0] + 1;
 152         size_t i;
 153
 154         /* If it appears that we are handling options, then make sure that
 155            all of the options specified are actually valid.  Otherwise, the
 156            string should just be echoed.  */
 157
 158         for (i = 0; temp[i]; i++)
 159           switch (temp[i])
 160             {
 161             case 'e': case 'E': case 'n':
 162               break;
 163             default:
 164               goto just_echo;
 165             }
 166
 167         if (i == 0)
 168           goto just_echo;
 169
 170         /* All of the options in TEMP are valid options to ECHO.
 171            Handle them. */
 172         while (*temp)
 173           switch (*temp++)
 174             {
 175             case 'e':
 176               do_v9 = true;
 177               break;
 178
 179             case 'E':
 180               do_v9 = false;
 181               break;
 182
 183             case 'n':
 184               display_return = false;
 185               break;
 186             }
 187
 188         argc--;
 189         argv++;
 190       }
 191
 192 just_echo:
 193
 194   if (do_v9)
 195     {
 196       while (argc > 0)
 197         {
 198           char const *s = argv[0];
 199           unsigned char c;
 200
 201           while ((c = *s++))
 202             {
 203               if (c == '\\' && *s)
 204                 {
 205                   switch (c = *s++)
 206                     {
 207                     case 'a': c = '\a'; break;
 208                     case 'b': c = '\b'; break;
 209                     case 'c': exit (EXIT_SUCCESS);
 210                     case 'e': c = '\x1B'; break;
 211                     case 'f': c = '\f'; break;
 212                     case 'n': c = '\n'; break;
 213                     case 'r': c = '\r'; break;
 214                     case 't': c = '\t'; break;
 215                     case 'v': c = '\v'; break;
 216                     case 'x':
 217                       {
 218                         unsigned char ch = *s;
 219                         if (! isxdigit (ch))
 220                           goto not_an_escape;
 221                         s++;
 222                         c = hextobin (ch);
 223                         ch = *s;
 224                         if (isxdigit (ch))
 225                           {
 226                             s++;
 227                             c = c * 16 + hextobin (ch);
 228                           }
 229                       }
 230                       break;
 231                     case '0':
 232                       c = 0;
 233                       if (! ('0' <= *s && *s <= '7'))
 234                         break;
 235                       c = *s++;
 236                       /* Fall through.  */
 237                     case '1': case '2': case '3':
 238                     case '4': case '5': case '6': case '7':
 239                       c -= '0';
 240                       if ('0' <= *s && *s <= '7')
 241                         c = c * 8 + (*s++ - '0');
 242                       if ('0' <= *s && *s <= '7')
 243                         c = c * 8 + (*s++ - '0');
 244                       break;
 245                     case '\\': break;
 246
 247                     not_an_escape:
 248                     default:  putchar ('\\'); break;
 249                     }
 250                 }
 251               putchar (c);
 252             }
 253           argc--;
 254           argv++;
 255           if (argc > 0)
 256             putchar (' ');
 257         }
 258     }
 259   else
 260     {
 261       while (argc > 0)
 262         {
 263           fputs (argv[0], stdout);
 264           argc--;
 265           argv++;
 266           if (argc > 0)
 267             putchar (' ');
 268         }
 269     }
 270
 271   if (display_return)
 272     putchar ('\n');
 273   exit (EXIT_SUCCESS);
 274 }