src/yes.c

   1 /* yes - output a string repeatedly until killed
   2    Copyright (C) 1991-2023 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 /* David MacKenzie <djm@gnu.ai.mit.edu> */
  18
  19 #include <config.h>
  20 #include <stdio.h>
  21 #include <sys/types.h>
  22
  23 #include "system.h"
  24
  25 #include "full-write.h"
  26 #include "long-options.h"
  27
  28 /* The official name of this program (e.g., no 'g' prefix).  */
  29 #define PROGRAM_NAME "yes"
  30
  31 #define AUTHORS proper_name ("David MacKenzie")
  32
  33 void
  34 usage (int status)
  35 {
  36   if (status != EXIT_SUCCESS)
  37     emit_try_help ();
  38   else
  39     {
  40       printf (_("\
  41 Usage: %s [STRING]...\n\
  42   or:  %s OPTION\n\
  43 "),
  44               program_name, program_name);
  45
  46       fputs (_("\
  47 Repeatedly output a line with all specified STRING(s), or 'y'.\n\
  48 \n\
  49 "), stdout);
  50       fputs (HELP_OPTION_DESCRIPTION, stdout);
  51       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  52       emit_ancillary_info (PROGRAM_NAME);
  53     }
  54   exit (status);
  55 }
  56
  57 int
  58 main (int argc, char **argv)
  59 {
  60   initialize_main (&argc, &argv);
  61   set_program_name (argv[0]);
  62   setlocale (LC_ALL, "");
  63   bindtextdomain (PACKAGE, LOCALEDIR);
  64   textdomain (PACKAGE);
  65
  66   atexit (close_stdout);
  67
  68   parse_gnu_standard_options_only (argc, argv, PROGRAM_NAME, PACKAGE_NAME,
  69                                    Version, true, usage, AUTHORS,
  70                                    (char const *) nullptr);
  71
  72   char **operands = argv + optind;
  73   char **operand_lim = argv + argc;
  74   if (optind == argc)
  75     *operand_lim++ = bad_cast ("y");
  76
  77   /* Buffer data locally once, rather than having the
  78      large overhead of stdio buffering each item.  */
  79   size_t bufalloc = 0;
  80   bool reuse_operand_strings = true;
  81   char **operandp = operands;
  82   do
  83     {
  84       size_t operand_len = strlen (*operandp);
  85       bufalloc += operand_len + 1;
  86       if (operandp + 1 < operand_lim
  87           && *operandp + operand_len + 1 != operandp[1])
  88         reuse_operand_strings = false;
  89     }
  90   while (++operandp < operand_lim);
  91
  92   /* Improve performance by using a buffer size greater than BUFSIZ / 2.  */
  93   if (bufalloc <= BUFSIZ / 2)
  94     {
  95       bufalloc = BUFSIZ;
  96       reuse_operand_strings = false;
  97     }
  98
  99   /* Fill the buffer with one copy of the output.  If possible, reuse
 100      the operands strings; this wins when the buffer would be large.  */
 101   char *buf = reuse_operand_strings ? *operands : xmalloc (bufalloc);
 102   size_t bufused = 0;
 103   operandp = operands;
 104   do
 105     {
 106       size_t operand_len = strlen (*operandp);
 107       if (! reuse_operand_strings)
 108         memcpy (buf + bufused, *operandp, operand_len);
 109       bufused += operand_len;
 110       buf[bufused++] = ' ';
 111     }
 112   while (++operandp < operand_lim);
 113   buf[bufused - 1] = '\n';
 114
 115   /* If a larger buffer was allocated, fill it by repeating the buffer
 116      contents.  */
 117   size_t copysize = bufused;
 118   for (size_t copies = bufalloc / copysize; --copies; )
 119     {
 120       memcpy (buf + bufused, buf, copysize);
 121       bufused += copysize;
 122     }
 123
 124   /* Repeatedly output the buffer until there is a write error; then fail.  */
 125   while (full_write (STDOUT_FILENO, buf, bufused) == bufused)
 126     continue;
 127   error (0, errno, _("standard output"));
 128   main_exit (EXIT_FAILURE);
 129 }