src/yes.c

   1 /* yes - output a string repeatedly until killed
   2    Copyright (C) 1991-2019 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 "error.h"
  26 #include "full-write.h"
  27 #include "long-options.h"
  28
  29 /* The official name of this program (e.g., no 'g' prefix).  */
  30 #define PROGRAM_NAME "yes"
  31
  32 #define AUTHORS proper_name ("David MacKenzie")
  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 [STRING]...\n\
  43   or:  %s OPTION\n\
  44 "),
  45               program_name, program_name);
  46
  47       fputs (_("\
  48 Repeatedly output a line with all specified STRING(s), or 'y'.\n\
  49 \n\
  50 "), stdout);
  51       fputs (HELP_OPTION_DESCRIPTION, stdout);
  52       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  53       emit_ancillary_info (PROGRAM_NAME);
  54     }
  55   exit (status);
  56 }
  57
  58 int
  59 main (int argc, char **argv)
  60 {
  61   initialize_main (&argc, &argv);
  62   set_program_name (argv[0]);
  63   setlocale (LC_ALL, "");
  64   bindtextdomain (PACKAGE, LOCALEDIR);
  65   textdomain (PACKAGE);
  66
  67   atexit (close_stdout);
  68
  69   parse_gnu_standard_options_only (argc, argv, PROGRAM_NAME, PACKAGE_NAME,
  70                                    Version, true, usage, AUTHORS,
  71                                    (char const *) NULL);
  72
  73   char **operands = argv + optind;
  74   char **operand_lim = argv + argc;
  75   if (optind == argc)
  76     *operand_lim++ = bad_cast ("y");
  77
  78   /* Buffer data locally once, rather than having the
  79      large overhead of stdio buffering each item.  */
  80   size_t bufalloc = 0;
  81   bool reuse_operand_strings = true;
  82   for (char **operandp = operands; operandp < operand_lim; operandp++)
  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
  91   /* Improve performance by using a buffer size greater than BUFSIZ / 2.  */
  92   if (bufalloc <= BUFSIZ / 2)
  93     {
  94       bufalloc = BUFSIZ;
  95       reuse_operand_strings = false;
  96     }
  97
  98   /* Fill the buffer with one copy of the output.  If possible, reuse
  99      the operands strings; this wins when the buffer would be large.  */
 100   char *buf = reuse_operand_strings ? *operands : xmalloc (bufalloc);
 101   size_t bufused = 0;
 102   for (char **operandp = operands; operandp < operand_lim; operandp++)
 103     {
 104       size_t operand_len = strlen (*operandp);
 105       if (! reuse_operand_strings)
 106         memcpy (buf + bufused, *operandp, operand_len);
 107       bufused += operand_len;
 108       buf[bufused++] = ' ';
 109     }
 110   buf[bufused - 1] = '\n';
 111
 112   /* If a larger buffer was allocated, fill it by repeating the buffer
 113      contents.  */
 114   size_t copysize = bufused;
 115   for (size_t copies = bufalloc / copysize; --copies; )
 116     {
 117       memcpy (buf + bufused, buf, copysize);
 118       bufused += copysize;
 119     }
 120
 121   /* Repeatedly output the buffer until there is a write error; then fail.  */
 122   while (full_write (STDOUT_FILENO, buf, bufused) == bufused)
 123     continue;
 124   error (0, errno, _("standard output"));
 125   return EXIT_FAILURE;
 126 }