src/echo.c

   1 /* echo.c, derived from code echo.c in Bash.
   2    Copyright (C) 1987-2013 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 <http://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18 #include <stdio.h>
  19 #include <sys/types.h>
  20 #include "system.h"
  21
  22 /* The official name of this program (e.g., no 'g' prefix).  */
  23 #define PROGRAM_NAME "echo"
  24
  25 #define AUTHORS \
  26   proper_name ("Brian Fox"), \
  27   proper_name ("Chet Ramey")
  28
  29 /* If true, interpret backslash escapes by default.  */
  30 #ifndef DEFAULT_ECHO_TO_XPG
  31 enum { DEFAULT_ECHO_TO_XPG = false };
  32 #endif
  33
  34 void
  35 usage (int status)
  36 {
  37   if (status != EXIT_SUCCESS)
  38     emit_try_help ();
  39   else
  40     {
  41       printf (_("\
  42 Usage: %s [SHORT-OPTION]... [STRING]...\n\
  43   or:  %s LONG-OPTION\n\
  44 "), program_name, program_name);
  45       fputs (_("\
  46 Echo the STRING(s) to standard output.\n\
  47 \n\
  48   -n             do not output the trailing newline\n\
  49 "), stdout);
  50       fputs (_(DEFAULT_ECHO_TO_XPG
  51                ? N_("\
  52   -e             enable interpretation of backslash escapes (default)\n\
  53   -E             disable interpretation of backslash escapes\n")
  54                : N_("\
  55   -e             enable interpretation of backslash escapes\n\
  56   -E             disable interpretation of backslash escapes (default)\n")),
  57              stdout);
  58       fputs (HELP_OPTION_DESCRIPTION, stdout);
  59       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  60       fputs (_("\
  61 \n\
  62 If -e is in effect, the following sequences are recognized:\n\
  63 \n\
  64 "), stdout);
  65       fputs (_("\
  66   \\\\      backslash\n\
  67   \\a      alert (BEL)\n\
  68   \\b      backspace\n\
  69   \\c      produce no further output\n\
  70   \\e      escape\n\
  71   \\f      form feed\n\
  72   \\n      new line\n\
  73   \\r      carriage return\n\
  74   \\t      horizontal tab\n\
  75   \\v      vertical tab\n\
  76 "), stdout);
  77       fputs (_("\
  78   \\0NNN   byte with octal value NNN (1 to 3 digits)\n\
  79   \\xHH    byte with hexadecimal value HH (1 to 2 digits)\n\
  80 "), stdout);
  81       printf (USAGE_BUILTIN_WARNING, PROGRAM_NAME);
  82       emit_ancillary_info ();
  83     }
  84   exit (status);
  85 }
  86
  87 /* Convert C from hexadecimal character to integer.  */
  88 static int
  89 hextobin (unsigned char c)
  90 {
  91   switch (c)
  92     {
  93     default: return c - '0';
  94     case 'a': case 'A': return 10;
  95     case 'b': case 'B': return 11;
  96     case 'c': case 'C': return 12;
  97     case 'd': case 'D': return 13;
  98     case 'e': case 'E': return 14;
  99     case 'f': case 'F': return 15;
 100     }
 101 }
 102
 103 /* Print the words in LIST to standard output.  If the first word is
 104    '-n', then don't print a trailing newline.  We also support the
 105    echo syntax from Version 9 unix systems. */
 106
 107 int
 108 main (int argc, char **argv)
 109 {
 110   bool display_return = true;
 111   bool allow_options =
 112     (! getenv ("POSIXLY_CORRECT")
 113      || (! DEFAULT_ECHO_TO_XPG && 1 < argc && STREQ (argv[1], "-n")));
 114
 115   /* System V machines already have a /bin/sh with a v9 behavior.
 116      Use the identical behavior for these machines so that the
 117      existing system shell scripts won't barf.  */
 118   bool do_v9 = DEFAULT_ECHO_TO_XPG;
 119
 120   initialize_main (&argc, &argv);
 121   set_program_name (argv[0]);
 122   setlocale (LC_ALL, "");
 123   bindtextdomain (PACKAGE, LOCALEDIR);
 124   textdomain (PACKAGE);
 125
 126   atexit (close_stdout);
 127
 128   /* We directly parse options, rather than use parse_long_options, in
 129      order to avoid accepting abbreviations.  */
 130   if (allow_options && argc == 2)
 131     {
 132       if (STREQ (argv[1], "--help"))
 133         usage (EXIT_SUCCESS);
 134
 135       if (STREQ (argv[1], "--version"))
 136         {
 137           version_etc (stdout, PROGRAM_NAME, PACKAGE_NAME, Version, AUTHORS,
 138                        (char *) NULL);
 139           exit (EXIT_SUCCESS);
 140         }
 141     }
 142
 143   --argc;
 144   ++argv;
 145
 146   if (allow_options)
 147     while (argc > 0 && *argv[0] == '-')
 148       {
 149         char const *temp = argv[0] + 1;
 150         size_t i;
 151
 152         /* If it appears that we are handling options, then make sure that
 153            all of the options specified are actually valid.  Otherwise, the
 154            string should just be echoed.  */
 155
 156         for (i = 0; temp[i]; i++)
 157           switch (temp[i])
 158             {
 159             case 'e': case 'E': case 'n':
 160               break;
 161             default:
 162               goto just_echo;
 163             }
 164
 165         if (i == 0)
 166           goto just_echo;
 167
 168         /* All of the options in TEMP are valid options to ECHO.
 169            Handle them. */
 170         while (*temp)
 171           switch (*temp++)
 172             {
 173             case 'e':
 174               do_v9 = true;
 175               break;
 176
 177             case 'E':
 178               do_v9 = false;
 179               break;
 180
 181             case 'n':
 182               display_return = false;
 183               break;
 184             }
 185
 186         argc--;
 187         argv++;
 188       }
 189
 190 just_echo:
 191
 192   if (do_v9)
 193     {
 194       while (argc > 0)
 195         {
 196           char const *s = argv[0];
 197           unsigned char c;
 198
 199           while ((c = *s++))
 200             {
 201               if (c == '\\' && *s)
 202                 {
 203                   switch (c = *s++)
 204                     {
 205                     case 'a': c = '\a'; break;
 206                     case 'b': c = '\b'; break;
 207                     case 'c': exit (EXIT_SUCCESS);
 208                     case 'e': c = '\x1B'; break;
 209                     case 'f': c = '\f'; break;
 210                     case 'n': c = '\n'; break;
 211                     case 'r': c = '\r'; break;
 212                     case 't': c = '\t'; break;
 213                     case 'v': c = '\v'; break;
 214                     case 'x':
 215                       {
 216                         unsigned char ch = *s;
 217                         if (! isxdigit (ch))
 218                           goto not_an_escape;
 219                         s++;
 220                         c = hextobin (ch);
 221                         ch = *s;
 222                         if (isxdigit (ch))
 223                           {
 224                             s++;
 225                             c = c * 16 + hextobin (ch);
 226                           }
 227                       }
 228                       break;
 229                     case '0':
 230                       c = 0;
 231                       if (! ('0' <= *s && *s <= '7'))
 232                         break;
 233                       c = *s++;
 234                       /* Fall through.  */
 235                     case '1': case '2': case '3':
 236                     case '4': case '5': case '6': case '7':
 237                       c -= '0';
 238                       if ('0' <= *s && *s <= '7')
 239                         c = c * 8 + (*s++ - '0');
 240                       if ('0' <= *s && *s <= '7')
 241                         c = c * 8 + (*s++ - '0');
 242                       break;
 243                     case '\\': break;
 244
 245                     not_an_escape:
 246                     default:  putchar ('\\'); break;
 247                     }
 248                 }
 249               putchar (c);
 250             }
 251           argc--;
 252           argv++;
 253           if (argc > 0)
 254             putchar (' ');
 255         }
 256     }
 257   else
 258     {
 259       while (argc > 0)
 260         {
 261           fputs (argv[0], stdout);
 262           argc--;
 263           argv++;
 264           if (argc > 0)
 265             putchar (' ');
 266         }
 267     }
 268
 269   if (display_return)
 270     putchar ('\n');
 271   exit (EXIT_SUCCESS);
 272 }