src/expand.c

   1 /* expand - convert tabs to spaces
   2    Copyright (C) 1989-2024 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 /* 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 <ctype.h>
  38 #include <stdio.h>
  39 #include <getopt.h>
  40 #include <sys/types.h>
  41 #include "system.h"
  42 #include "expand-common.h"
  43
  44 /* The official name of this program (e.g., no 'g' prefix).  */
  45 #define PROGRAM_NAME "expand"
  46
  47 #define AUTHORS proper_name ("David MacKenzie")
  48
  49 static char const shortopts[] = "it:0::1::2::3::4::5::6::7::8::9::";
  50
  51 static struct option const longopts[] =
  52 {
  53   {"tabs", required_argument, nullptr, 't'},
  54   {"initial", no_argument, nullptr, 'i'},
  55   {GETOPT_HELP_OPTION_DECL},
  56   {GETOPT_VERSION_OPTION_DECL},
  57   {nullptr, 0, nullptr, 0}
  58 };
  59
  60 void
  61 usage (int status)
  62 {
  63   if (status != EXIT_SUCCESS)
  64     emit_try_help ();
  65   else
  66     {
  67       printf (_("\
  68 Usage: %s [OPTION]... [FILE]...\n\
  69 "),
  70               program_name);
  71       fputs (_("\
  72 Convert tabs in each FILE to spaces, writing to standard output.\n\
  73 "), stdout);
  74
  75       emit_stdin_note ();
  76       emit_mandatory_arg_note ();
  77
  78       fputs (_("\
  79   -i, --initial    do not convert tabs after non blanks\n\
  80   -t, --tabs=N     have tabs N characters apart, not 8\n\
  81 "), stdout);
  82       emit_tab_list_info ();
  83       fputs (HELP_OPTION_DESCRIPTION, stdout);
  84       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  85       emit_ancillary_info (PROGRAM_NAME);
  86     }
  87   exit (status);
  88 }
  89
  90
  91 /* Change tabs to spaces, writing to stdout.
  92    Read each file in 'file_list', in order.  */
  93
  94 static void
  95 expand (void)
  96 {
  97   /* Input stream.  */
  98   FILE *fp = next_file (nullptr);
  99
 100   if (!fp)
 101     return;
 102
 103   while (true)
 104     {
 105       /* Input character, or EOF.  */
 106       int c;
 107
 108       /* If true, perform translations.  */
 109       bool convert = true;
 110
 111
 112       /* The following variables have valid values only when CONVERT
 113          is true:  */
 114
 115       /* Column of next input character.  */
 116       uintmax_t column = 0;
 117
 118       /* Index in TAB_LIST of next tab stop to examine.  */
 119       size_t tab_index = 0;
 120
 121
 122       /* Convert a line of text.  */
 123
 124       do
 125         {
 126           while ((c = getc (fp)) < 0 && (fp = next_file (fp)))
 127             continue;
 128
 129           if (convert)
 130             {
 131               if (c == '\t')
 132                 {
 133                   /* Column the next input tab stop is on.  */
 134                   uintmax_t next_tab_column;
 135                   bool last_tab;
 136
 137                   next_tab_column = get_next_tab_column (column, &tab_index,
 138                                                          &last_tab);
 139
 140                   if (last_tab)
 141                     next_tab_column = column + 1;
 142
 143                   if (next_tab_column < column)
 144                     error (EXIT_FAILURE, 0, _("input line is too long"));
 145
 146                   while (++column < next_tab_column)
 147                     if (putchar (' ') < 0)
 148                       write_error ();
 149
 150                   c = ' ';
 151                 }
 152               else if (c == '\b')
 153                 {
 154                   /* Go back one column, and force recalculation of the
 155                      next tab stop.  */
 156                   column -= !!column;
 157                   tab_index -= !!tab_index;
 158                 }
 159               else
 160                 {
 161                   column++;
 162                   if (!column)
 163                     error (EXIT_FAILURE, 0, _("input line is too long"));
 164                 }
 165
 166               convert &= convert_entire_line || !! isblank (c);
 167             }
 168
 169           if (c < 0)
 170             return;
 171
 172           if (putchar (c) < 0)
 173             write_error ();
 174         }
 175       while (c != '\n');
 176     }
 177 }
 178
 179 int
 180 main (int argc, char **argv)
 181 {
 182   int c;
 183
 184   initialize_main (&argc, &argv);
 185   set_program_name (argv[0]);
 186   setlocale (LC_ALL, "");
 187   bindtextdomain (PACKAGE, LOCALEDIR);
 188   textdomain (PACKAGE);
 189
 190   atexit (close_stdout);
 191   convert_entire_line = true;
 192
 193   while ((c = getopt_long (argc, argv, shortopts, longopts, nullptr)) != -1)
 194     {
 195       switch (c)
 196         {
 197         case 'i':
 198           convert_entire_line = false;
 199           break;
 200
 201         case 't':
 202           parse_tab_stops (optarg);
 203           break;
 204
 205         case '0': case '1': case '2': case '3': case '4':
 206         case '5': case '6': case '7': case '8': case '9':
 207           if (optarg)
 208             parse_tab_stops (optarg - 1);
 209           else
 210             {
 211               char tab_stop[2];
 212               tab_stop[0] = c;
 213               tab_stop[1] = '\0';
 214               parse_tab_stops (tab_stop);
 215             }
 216           break;
 217
 218         case_GETOPT_HELP_CHAR;
 219
 220         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 221
 222         default:
 223           usage (EXIT_FAILURE);
 224         }
 225     }
 226
 227   finalize_tab_stops ();
 228
 229   set_file_list (optind < argc ? &argv[optind] : nullptr);
 230
 231   expand ();
 232
 233   cleanup_file_list_stdin ();
 234
 235   return exit_status;
 236 }