src/yes.c

   1 /* yes - output a string repeatedly until killed
   2    Copyright (C) 1991-2017 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 /* David MacKenzie <djm@gnu.ai.mit.edu> */
  18
  19 #include <config.h>
  20 #include <stdio.h>
  21 #include <sys/types.h>
  22 #include <getopt.h>
  23
  24 #include "system.h"
  25
  26 #include "error.h"
  27 #include "full-write.h"
  28 #include "long-options.h"
  29
  30 /* The official name of this program (e.g., no 'g' prefix).  */
  31 #define PROGRAM_NAME "yes"
  32
  33 #define AUTHORS proper_name ("David MacKenzie")
  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 [STRING]...\n\
  44   or:  %s OPTION\n\
  45 "),
  46               program_name, program_name);
  47
  48       fputs (_("\
  49 Repeatedly output a line with all specified STRING(s), or 'y'.\n\
  50 \n\
  51 "), stdout);
  52       fputs (HELP_OPTION_DESCRIPTION, stdout);
  53       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  54       emit_ancillary_info (PROGRAM_NAME);
  55     }
  56   exit (status);
  57 }
  58
  59 int
  60 main (int argc, char **argv)
  61 {
  62   initialize_main (&argc, &argv);
  63   set_program_name (argv[0]);
  64   setlocale (LC_ALL, "");
  65   bindtextdomain (PACKAGE, LOCALEDIR);
  66   textdomain (PACKAGE);
  67
  68   atexit (close_stdout);
  69
  70   parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE_NAME, Version,
  71                       usage, AUTHORS, (char const *) NULL);
  72   if (getopt_long (argc, argv, "+", NULL, NULL) != -1)
  73     usage (EXIT_FAILURE);
  74
  75   char **operands = argv + optind;
  76   char **operand_lim = argv + argc;
  77   if (optind == argc)
  78     *operand_lim++ = bad_cast ("y");
  79
  80   /* Buffer data locally once, rather than having the
  81      large overhead of stdio buffering each item.  */
  82   size_t bufalloc = 0;
  83   bool reuse_operand_strings = true;
  84   for (char **operandp = operands; operandp < operand_lim; operandp++)
  85     {
  86       size_t operand_len = strlen (*operandp);
  87       bufalloc += operand_len + 1;
  88       if (operandp + 1 < operand_lim
  89           && *operandp + operand_len + 1 != operandp[1])
  90         reuse_operand_strings = false;
  91     }
  92
  93   /* Improve performance by using a buffer size greater than BUFSIZ / 2.  */
  94   if (bufalloc <= BUFSIZ / 2)
  95     {
  96       bufalloc = BUFSIZ;
  97       reuse_operand_strings = false;
  98     }
  99
 100   /* Fill the buffer with one copy of the output.  If possible, reuse
 101      the operands strings; this wins when the buffer would be large.  */
 102   char *buf = reuse_operand_strings ? *operands : xmalloc (bufalloc);
 103   size_t bufused = 0;
 104   for (char **operandp = operands; operandp < operand_lim; operandp++)
 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   buf[bufused - 1] = '\n';
 113
 114   /* If a larger buffer was allocated, fill it by repeating the buffer
 115      contents.  */
 116   size_t copysize = bufused;
 117   for (size_t copies = bufalloc / copysize; --copies; )
 118     {
 119       memcpy (buf + bufused, buf, copysize);
 120       bufused += copysize;
 121     }
 122
 123   /* Repeatedly output the buffer until there is a write error; then fail.  */
 124   while (full_write (STDOUT_FILENO, buf, bufused) == bufused)
 125     continue;
 126   error (0, errno, _("standard output"));
 127   return EXIT_FAILURE;
 128 }