src/echo.c

   1 /* echo.c, derived from code echo.c in Bash.
   2    Copyright (C) 1987, 1989, 1991-1997, 1999-2005, 2007-2012 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     emit_try_help ();
  40   else
  41     {
  42       printf (_("\
  43 Usage: %s [SHORT-OPTION]... [STRING]...\n\
  44   or:  %s LONG-OPTION\n\
  45 "), program_name, program_name);
  46       fputs (_("\
  47 Echo the STRING(s) to standard output.\n\
  48 \n\
  49   -n             do not output the trailing newline\n\
  50 "), stdout);
  51       fputs (_(DEFAULT_ECHO_TO_XPG
  52                ? N_("\
  53   -e             enable interpretation of backslash escapes (default)\n\
  54   -E             disable interpretation of backslash escapes\n")
  55                : N_("\
  56   -e             enable interpretation of backslash escapes\n\
  57   -E             disable interpretation of backslash escapes (default)\n")),
  58              stdout);
  59       fputs (HELP_OPTION_DESCRIPTION, stdout);
  60       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  61       fputs (_("\
  62 \n\
  63 If -e is in effect, the following sequences are recognized:\n\
  64 \n\
  65 "), stdout);
  66       fputs (_("\
  67   \\\\      backslash\n\
  68   \\a      alert (BEL)\n\
  69   \\b      backspace\n\
  70   \\c      produce no further output\n\
  71   \\e      escape\n\
  72   \\f      form feed\n\
  73   \\n      new line\n\
  74   \\r      carriage return\n\
  75   \\t      horizontal tab\n\
  76   \\v      vertical tab\n\
  77 "), stdout);
  78       fputs (_("\
  79   \\0NNN   byte with octal value NNN (1 to 3 digits)\n\
  80   \\xHH    byte with hexadecimal value HH (1 to 2 digits)\n\
  81 "), stdout);
  82       printf (USAGE_BUILTIN_WARNING, PROGRAM_NAME);
  83       emit_ancillary_info ();
  84     }
  85   exit (status);
  86 }
  87
  88 /* Convert C from hexadecimal character to integer.  */
  89 static int
  90 hextobin (unsigned char c)
  91 {
  92   switch (c)
  93     {
  94     default: return c - '0';
  95     case 'a': case 'A': return 10;
  96     case 'b': case 'B': return 11;
  97     case 'c': case 'C': return 12;
  98     case 'd': case 'D': return 13;
  99     case 'e': case 'E': return 14;
 100     case 'f': case 'F': return 15;
 101     }
 102 }
 103
 104 /* Print the words in LIST to standard output.  If the first word is
 105    `-n', then don't print a trailing newline.  We also support the
 106    echo syntax from Version 9 unix systems. */
 107
 108 int
 109 main (int argc, char **argv)
 110 {
 111   bool display_return = true;
 112   bool allow_options =
 113     (! getenv ("POSIXLY_CORRECT")
 114      || (! DEFAULT_ECHO_TO_XPG && 1 < argc && STREQ (argv[1], "-n")));
 115
 116   /* System V machines already have a /bin/sh with a v9 behavior.
 117      Use the identical behavior for these machines so that the
 118      existing system shell scripts won't barf.  */
 119   bool do_v9 = DEFAULT_ECHO_TO_XPG;
 120
 121   initialize_main (&argc, &argv);
 122   set_program_name (argv[0]);
 123   setlocale (LC_ALL, "");
 124   bindtextdomain (PACKAGE, LOCALEDIR);
 125   textdomain (PACKAGE);
 126
 127   atexit (close_stdout);
 128
 129   /* We directly parse options, rather than use parse_long_options, in
 130      order to avoid accepting abbreviations.  */
 131   if (allow_options && argc == 2)
 132     {
 133       if (STREQ (argv[1], "--help"))
 134         usage (EXIT_SUCCESS);
 135
 136       if (STREQ (argv[1], "--version"))
 137         {
 138           version_etc (stdout, PROGRAM_NAME, PACKAGE_NAME, Version, AUTHORS,
 139                        (char *) NULL);
 140           exit (EXIT_SUCCESS);
 141         }
 142     }
 143
 144   --argc;
 145   ++argv;
 146
 147   if (allow_options)
 148     while (argc > 0 && *argv[0] == '-')
 149       {
 150         char const *temp = argv[0] + 1;
 151         size_t i;
 152
 153         /* If it appears that we are handling options, then make sure that
 154            all of the options specified are actually valid.  Otherwise, the
 155            string should just be echoed.  */
 156
 157         for (i = 0; temp[i]; i++)
 158           switch (temp[i])
 159             {
 160             case 'e': case 'E': case 'n':
 161               break;
 162             default:
 163               goto just_echo;
 164             }
 165
 166         if (i == 0)
 167           goto just_echo;
 168
 169         /* All of the options in TEMP are valid options to ECHO.
 170            Handle them. */
 171         while (*temp)
 172           switch (*temp++)
 173             {
 174             case 'e':
 175               do_v9 = true;
 176               break;
 177
 178             case 'E':
 179               do_v9 = false;
 180               break;
 181
 182             case 'n':
 183               display_return = false;
 184               break;
 185             }
 186
 187         argc--;
 188         argv++;
 189       }
 190
 191 just_echo:
 192
 193   if (do_v9)
 194     {
 195       while (argc > 0)
 196         {
 197           char const *s = argv[0];
 198           unsigned char c;
 199
 200           while ((c = *s++))
 201             {
 202               if (c == '\\' && *s)
 203                 {
 204                   switch (c = *s++)
 205                     {
 206                     case 'a': c = '\a'; break;
 207                     case 'b': c = '\b'; break;
 208                     case 'c': exit (EXIT_SUCCESS);
 209                     case 'e': c = '\x1B'; break;
 210                     case 'f': c = '\f'; break;
 211                     case 'n': c = '\n'; break;
 212                     case 'r': c = '\r'; break;
 213                     case 't': c = '\t'; break;
 214                     case 'v': c = '\v'; break;
 215                     case 'x':
 216                       {
 217                         unsigned char ch = *s;
 218                         if (! isxdigit (ch))
 219                           goto not_an_escape;
 220                         s++;
 221                         c = hextobin (ch);
 222                         ch = *s;
 223                         if (isxdigit (ch))
 224                           {
 225                             s++;
 226                             c = c * 16 + hextobin (ch);
 227                           }
 228                       }
 229                       break;
 230                     case '0':
 231                       c = 0;
 232                       if (! ('0' <= *s && *s <= '7'))
 233                         break;
 234                       c = *s++;
 235                       /* Fall through.  */
 236                     case '1': case '2': case '3':
 237                     case '4': case '5': case '6': case '7':
 238                       c -= '0';
 239                       if ('0' <= *s && *s <= '7')
 240                         c = c * 8 + (*s++ - '0');
 241                       if ('0' <= *s && *s <= '7')
 242                         c = c * 8 + (*s++ - '0');
 243                       break;
 244                     case '\\': break;
 245
 246                     not_an_escape:
 247                     default:  putchar ('\\'); break;
 248                     }
 249                 }
 250               putchar (c);
 251             }
 252           argc--;
 253           argv++;
 254           if (argc > 0)
 255             putchar (' ');
 256         }
 257     }
 258   else
 259     {
 260       while (argc > 0)
 261         {
 262           fputs (argv[0], stdout);
 263           argc--;
 264           argv++;
 265           if (argc > 0)
 266             putchar (' ');
 267         }
 268     }
 269
 270   if (display_return)
 271     putchar ('\n');
 272   exit (EXIT_SUCCESS);
 273 }