src/expand.c

   1 /* expand - convert tabs to spaces
   2    Copyright (C) 1989-2017 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 <https://www.gnu.org/licenses/>.  */
  16
  17 /* By default, convert all tabs to spaces.
  18    Preserves backspace characters in the output; they decrement the
  19    column count for tab calculations.
  20    The default action is equivalent to -8.
  21
  22    Options:
  23    --tabs=tab1[,tab2[,...]]
  24    -t tab1[,tab2[,...]]
  25    -tab1[,tab2[,...]]   If only one tab stop is given, set the tabs tab1
  26                         columns apart instead of the default 8.  Otherwise,
  27                         set the tabs at columns tab1, tab2, etc. (numbered from
  28                         0); replace any tabs beyond the tab stops given with
  29                         single spaces.
  30    --initial
  31    -i                   Only convert initial tabs on each line to spaces.
  32
  33    David MacKenzie <djm@gnu.ai.mit.edu> */
  34
  35 #include <config.h>
  36
  37 #include <stdio.h>
  38 #include <getopt.h>
  39 #include <sys/types.h>
  40 #include "system.h"
  41 #include "die.h"
  42 #include "xstrndup.h"
  43
  44 #include "expand-common.h"
  45
  46 /* The official name of this program (e.g., no 'g' prefix).  */
  47 #define PROGRAM_NAME "expand"
  48
  49 #define AUTHORS proper_name ("David MacKenzie")
  50
  51 static char const shortopts[] = "it:0::1::2::3::4::5::6::7::8::9::";
  52
  53 static struct option const longopts[] =
  54 {
  55   {"tabs", required_argument, NULL, 't'},
  56   {"initial", no_argument, NULL, 'i'},
  57   {GETOPT_HELP_OPTION_DECL},
  58   {GETOPT_VERSION_OPTION_DECL},
  59   {NULL, 0, NULL, 0}
  60 };
  61
  62 void
  63 usage (int status)
  64 {
  65   if (status != EXIT_SUCCESS)
  66     emit_try_help ();
  67   else
  68     {
  69       printf (_("\
  70 Usage: %s [OPTION]... [FILE]...\n\
  71 "),
  72               program_name);
  73       fputs (_("\
  74 Convert tabs in each FILE to spaces, writing to standard output.\n\
  75 "), stdout);
  76
  77       emit_stdin_note ();
  78       emit_mandatory_arg_note ();
  79
  80       fputs (_("\
  81   -i, --initial    do not convert tabs after non blanks\n\
  82   -t, --tabs=N     have tabs N characters apart, not 8\n\
  83 "), stdout);
  84       emit_tab_list_info ();
  85       fputs (HELP_OPTION_DESCRIPTION, stdout);
  86       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  87       emit_ancillary_info (PROGRAM_NAME);
  88     }
  89   exit (status);
  90 }
  91
  92
  93 /* Change tabs to spaces, writing to stdout.
  94    Read each file in 'file_list', in order.  */
  95
  96 static void
  97 expand (void)
  98 {
  99   /* Input stream.  */
 100   FILE *fp = next_file (NULL);
 101
 102   if (!fp)
 103     return;
 104
 105   while (true)
 106     {
 107       /* Input character, or EOF.  */
 108       int c;
 109
 110       /* If true, perform translations.  */
 111       bool convert = true;
 112
 113
 114       /* The following variables have valid values only when CONVERT
 115          is true:  */
 116
 117       /* Column of next input character.  */
 118       uintmax_t column = 0;
 119
 120       /* Index in TAB_LIST of next tab stop to examine.  */
 121       size_t tab_index = 0;
 122
 123
 124       /* Convert a line of text.  */
 125
 126       do
 127         {
 128           while ((c = getc (fp)) < 0 && (fp = next_file (fp)))
 129             continue;
 130
 131           if (convert)
 132             {
 133               if (c == '\t')
 134                 {
 135                   /* Column the next input tab stop is on.  */
 136                   uintmax_t next_tab_column;
 137                   bool last_tab IF_LINT (=0);
 138
 139                   next_tab_column = get_next_tab_column (column, &tab_index,
 140                                                          &last_tab);
 141
 142                   if (last_tab)
 143                     next_tab_column = column + 1;
 144
 145                   if (next_tab_column < column)
 146                     die (EXIT_FAILURE, 0, _("input line is too long"));
 147
 148                   while (++column < next_tab_column)
 149                     if (putchar (' ') < 0)
 150                       die (EXIT_FAILURE, errno, _("write error"));
 151
 152                   c = ' ';
 153                 }
 154               else if (c == '\b')
 155                 {
 156                   /* Go back one column, and force recalculation of the
 157                      next tab stop.  */
 158                   column -= !!column;
 159                   tab_index -= !!tab_index;
 160                 }
 161               else
 162                 {
 163                   column++;
 164                   if (!column)
 165                     die (EXIT_FAILURE, 0, _("input line is too long"));
 166                 }
 167
 168               convert &= convert_entire_line || !! isblank (c);
 169             }
 170
 171           if (c < 0)
 172             return;
 173
 174           if (putchar (c) < 0)
 175             die (EXIT_FAILURE, errno, _("write error"));
 176         }
 177       while (c != '\n');
 178     }
 179 }
 180
 181 int
 182 main (int argc, char **argv)
 183 {
 184   int c;
 185
 186   initialize_main (&argc, &argv);
 187   set_program_name (argv[0]);
 188   setlocale (LC_ALL, "");
 189   bindtextdomain (PACKAGE, LOCALEDIR);
 190   textdomain (PACKAGE);
 191
 192   atexit (close_stdout);
 193   convert_entire_line = true;
 194
 195   while ((c = getopt_long (argc, argv, shortopts, longopts, NULL)) != -1)
 196     {
 197       switch (c)
 198         {
 199         case 'i':
 200           convert_entire_line = false;
 201           break;
 202
 203         case 't':
 204           parse_tab_stops (optarg);
 205           break;
 206
 207         case '0': case '1': case '2': case '3': case '4':
 208         case '5': case '6': case '7': case '8': case '9':
 209           if (optarg)
 210             parse_tab_stops (optarg - 1);
 211           else
 212             {
 213               char tab_stop[2];
 214               tab_stop[0] = c;
 215               tab_stop[1] = '\0';
 216               parse_tab_stops (tab_stop);
 217             }
 218           break;
 219
 220         case_GETOPT_HELP_CHAR;
 221
 222         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 223
 224         default:
 225           usage (EXIT_FAILURE);
 226         }
 227     }
 228
 229   finalize_tab_stops ();
 230
 231   set_file_list ( (optind < argc) ? &argv[optind] : NULL);
 232
 233   expand ();
 234
 235   cleanup_file_list_stdin ();
 236
 237   return exit_status;
 238 }