src/echo.c

   1 /* echo.c, derived from code echo.c in Bash.
   2    Copyright (C) 1987-2024 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 #include <config.h>
  18 #include <stdio.h>
  19 #include <sys/types.h>
  20 #include "system.h"
  21 #include "assure.h"
  22 #include "c-ctype.h"
  23
  24 /* The official name of this program (e.g., no 'g' prefix).  */
  25 #define PROGRAM_NAME "echo"
  26
  27 #define AUTHORS \
  28   proper_name ("Brian Fox"), \
  29   proper_name ("Chet Ramey")
  30
  31 /* If true, interpret backslash escapes by default.  */
  32 #ifndef DEFAULT_ECHO_TO_XPG
  33 enum { DEFAULT_ECHO_TO_XPG = false };
  34 #endif
  35
  36 void
  37 usage (int status)
  38 {
  39   /* STATUS should always be EXIT_SUCCESS (unlike in most other
  40      utilities which would call emit_try_help otherwise).  */
  41   affirm (status == EXIT_SUCCESS);
  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   fputs (_("\n\
  85 Consider using the 'printf' command instead,\n\
  86 as it avoids problems when outputting option-like strings.\n\
  87 "), stdout);
  88   emit_ancillary_info (PROGRAM_NAME);
  89   exit (status);
  90 }
  91
  92 /* Convert C from hexadecimal character to integer.  */
  93 static int
  94 hextobin (unsigned char c)
  95 {
  96   switch (c)
  97     {
  98     default: return c - '0';
  99     case 'a': case 'A': return 10;
 100     case 'b': case 'B': return 11;
 101     case 'c': case 'C': return 12;
 102     case 'd': case 'D': return 13;
 103     case 'e': case 'E': return 14;
 104     case 'f': case 'F': return 15;
 105     }
 106 }
 107
 108 /* Print the words in LIST to standard output.  If the first word is
 109    '-n', then don't print a trailing newline.  We also support the
 110    echo syntax from Version 9 unix systems. */
 111
 112 int
 113 main (int argc, char **argv)
 114 {
 115   bool display_return = true;
 116   bool posixly_correct = !!getenv ("POSIXLY_CORRECT");
 117   bool allow_options =
 118     (! posixly_correct
 119      || (! DEFAULT_ECHO_TO_XPG && 1 < argc && STREQ (argv[1], "-n")));
 120
 121   /* System V machines already have a /bin/sh with a v9 behavior.
 122      Use the identical behavior for these machines so that the
 123      existing system shell scripts won't barf.  */
 124   bool do_v9 = DEFAULT_ECHO_TO_XPG;
 125
 126   initialize_main (&argc, &argv);
 127   set_program_name (argv[0]);
 128   setlocale (LC_ALL, "");
 129   bindtextdomain (PACKAGE, LOCALEDIR);
 130   textdomain (PACKAGE);
 131
 132   atexit (close_stdout);
 133
 134   /* We directly parse options, rather than use parse_long_options, in
 135      order to avoid accepting abbreviations.  */
 136   if (allow_options && argc == 2)
 137     {
 138       if (STREQ (argv[1], "--help"))
 139         usage (EXIT_SUCCESS);
 140
 141       if (STREQ (argv[1], "--version"))
 142         {
 143           version_etc (stdout, PROGRAM_NAME, PACKAGE_NAME, Version, AUTHORS,
 144                        (char *) nullptr);
 145           return EXIT_SUCCESS;
 146         }
 147     }
 148
 149   --argc;
 150   ++argv;
 151
 152   if (allow_options)
 153     while (argc > 0 && *argv[0] == '-')
 154       {
 155         char const *temp = argv[0] + 1;
 156         size_t i;
 157
 158         /* If it appears that we are handling options, then make sure that
 159            all of the options specified are actually valid.  Otherwise, the
 160            string should just be echoed.  */
 161
 162         for (i = 0; temp[i]; i++)
 163           switch (temp[i])
 164             {
 165             case 'e': case 'E': case 'n':
 166               break;
 167             default:
 168               goto just_echo;
 169             }
 170
 171         if (i == 0)
 172           goto just_echo;
 173
 174         /* All of the options in TEMP are valid options to ECHO.
 175            Handle them. */
 176         while (*temp)
 177           switch (*temp++)
 178             {
 179             case 'e':
 180               do_v9 = true;
 181               break;
 182
 183             case 'E':
 184               do_v9 = false;
 185               break;
 186
 187             case 'n':
 188               display_return = false;
 189               break;
 190             }
 191
 192         argc--;
 193         argv++;
 194       }
 195
 196 just_echo:
 197
 198   if (do_v9 || posixly_correct)
 199     {
 200       while (argc > 0)
 201         {
 202           char const *s = argv[0];
 203           unsigned char c;
 204
 205           while ((c = *s++))
 206             {
 207               if (c == '\\' && *s)
 208                 {
 209                   switch (c = *s++)
 210                     {
 211                     case 'a': c = '\a'; break;
 212                     case 'b': c = '\b'; break;
 213                     case 'c': return EXIT_SUCCESS;
 214                     case 'e': c = '\x1B'; break;
 215                     case 'f': c = '\f'; break;
 216                     case 'n': c = '\n'; break;
 217                     case 'r': c = '\r'; break;
 218                     case 't': c = '\t'; break;
 219                     case 'v': c = '\v'; break;
 220                     case 'x':
 221                       {
 222                         unsigned char ch = *s;
 223                         if (! c_isxdigit (ch))
 224                           goto not_an_escape;
 225                         s++;
 226                         c = hextobin (ch);
 227                         ch = *s;
 228                         if (c_isxdigit (ch))
 229                           {
 230                             s++;
 231                             c = c * 16 + hextobin (ch);
 232                           }
 233                       }
 234                       break;
 235                     case '0':
 236                       c = 0;
 237                       if (! ('0' <= *s && *s <= '7'))
 238                         break;
 239                       c = *s++;
 240                       FALLTHROUGH;
 241                     case '1': case '2': case '3':
 242                     case '4': case '5': case '6': case '7':
 243                       c -= '0';
 244                       if ('0' <= *s && *s <= '7')
 245                         c = c * 8 + (*s++ - '0');
 246                       if ('0' <= *s && *s <= '7')
 247                         c = c * 8 + (*s++ - '0');
 248                       break;
 249                     case '\\': break;
 250
 251                     not_an_escape:
 252                     default:  putchar ('\\'); break;
 253                     }
 254                 }
 255               putchar (c);
 256             }
 257           argc--;
 258           argv++;
 259           if (argc > 0)
 260             putchar (' ');
 261         }
 262     }
 263   else
 264     {
 265       while (argc > 0)
 266         {
 267           fputs (argv[0], stdout);
 268           argc--;
 269           argv++;
 270           if (argc > 0)
 271             putchar (' ');
 272         }
 273     }
 274
 275   if (display_return)
 276     putchar ('\n');
 277   return EXIT_SUCCESS;
 278 }