1 /* fold -- wrap each input line to fit in specified width.
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 /* Written by David MacKenzie, djm@gnu.ai.mit.edu. */
18
19 #include <config.h>
20
21 #include <stdio.h>
22 #include <getopt.h>
23 #include <sys/types.h>
24
25 #include "system.h"
26 #include "fadvise.h"
27 #include "xdectoint.h"
28
29 #define TAB_WIDTH 8
30
31 /* The official name of this program (e.g., no 'g' prefix). */
32 #define PROGRAM_NAME "fold"
33
34 #define AUTHORS proper_name ("David MacKenzie")
35
36 /* If nonzero, try to break on whitespace. */
37 static bool break_spaces;
38
39 /* If nonzero, count bytes, not column positions. */
40 static bool count_bytes;
41
42 /* If nonzero, at least one of the files we read was standard input. */
43 static bool have_read_stdin;
44
45 static char const shortopts[] = "bsw:0::1::2::3::4::5::6::7::8::9::";
46
47 static struct option const longopts[] =
48 {
49 {"bytes", no_argument, nullptr, 'b'},
50 {"spaces", no_argument, nullptr, 's'},
51 {"width", required_argument, nullptr, 'w'},
52 {GETOPT_HELP_OPTION_DECL},
53 {GETOPT_VERSION_OPTION_DECL},
54 {nullptr, 0, nullptr, 0}
55 };
56
57 void
58 usage (int status)
59 {
60 if (status != EXIT_SUCCESS)
61 emit_try_help ();
62 else
63 {
64 printf (_("\
65 Usage: %s [OPTION]... [FILE]...\n\
66 "),
67 program_name);
68 fputs (_("\
69 Wrap input lines in each FILE, writing to standard output.\n\
70 "), stdout);
71
72 emit_stdin_note ();
73 emit_mandatory_arg_note ();
74
75 fputs (_("\
76 -b, --bytes count bytes rather than columns\n\
77 -s, --spaces break at spaces\n\
78 -w, --width=WIDTH use WIDTH columns instead of 80\n\
79 "), stdout);
80 fputs (HELP_OPTION_DESCRIPTION, stdout);
81 fputs (VERSION_OPTION_DESCRIPTION, stdout);
82 emit_ancillary_info (PROGRAM_NAME);
83 }
84 exit (status);
85 }
86
87 /* Assuming the current column is COLUMN, return the column that
88 printing C will move the cursor to.
89 The first column is 0. */
90
91 static size_t
92 adjust_column (size_t column, char c)
93 {
94 if (!count_bytes)
95 {
96 if (c == '\b')
97 {
98 if (column > 0)
99 column--;
100 }
101 else if (c == '\r')
102 column = 0;
103 else if (c == '\t')
104 column += TAB_WIDTH - column % TAB_WIDTH;
105 else /* if (isprint (c)) */
106 column++;
107 }
108 else
109 column++;
110 return column;
111 }
112
113 /* Fold file FILENAME, or standard input if FILENAME is "-",
114 to stdout, with maximum line length WIDTH.
115 Return true if successful. */
116
117 static bool
118 fold_file (char const *filename, size_t width)
119 {
120 FILE *istream;
121 int c;
122 size_t column = 0; /* Screen column where next char will go. */
123 size_t offset_out = 0; /* Index in 'line_out' for next char. */
124 static char *line_out = nullptr;
125 static size_t allocated_out = 0;
126 int saved_errno;
127
128 if (STREQ (filename, "-"))
129 {
130 istream = stdin;
131 have_read_stdin = true;
132 }
133 else
134 istream = fopen (filename, "r");
135
136 if (istream == nullptr)
137 {
138 error (0, errno, "%s", quotef (filename));
139 return false;
140 }
141
142 fadvise (istream, FADVISE_SEQUENTIAL);
143
144 while ((c = getc (istream)) != EOF)
145 {
146 if (offset_out + 1 >= allocated_out)
147 line_out = X2REALLOC (line_out, &allocated_out);
148
149 if (c == '\n')
150 {
151 line_out[offset_out++] = c;
152 fwrite (line_out, sizeof (char), offset_out, stdout);
153 column = offset_out = 0;
154 continue;
155 }
156
157 rescan:
158 column = adjust_column (column, c);
159
160 if (column > width)
161 {
162 /* This character would make the line too long.
163 Print the line plus a newline, and make this character
164 start the next line. */
165 if (break_spaces)
166 {
167 bool found_blank = false;
168 size_t logical_end = offset_out;
169
170 /* Look for the last blank. */
171 while (logical_end)
172 {
173 --logical_end;
174 if (isblank (to_uchar (line_out[logical_end])))
175 {
176 found_blank = true;
177 break;
178 }
179 }
180
181 if (found_blank)
182 {
183 size_t i;
184
185 /* Found a blank. Don't output the part after it. */
186 logical_end++;
187 fwrite (line_out, sizeof (char), (size_t) logical_end,
188 stdout);
189 putchar ('\n');
190 /* Move the remainder to the beginning of the next line.
191 The areas being copied here might overlap. */
192 memmove (line_out, line_out + logical_end,
193 offset_out - logical_end);
194 offset_out -= logical_end;
195 for (column = i = 0; i < offset_out; i++)
196 column = adjust_column (column, line_out[i]);
197 goto rescan;
198 }
199 }
200
201 if (offset_out == 0)
202 {
203 line_out[offset_out++] = c;
204 continue;
205 }
206
207 line_out[offset_out++] = '\n';
208 fwrite (line_out, sizeof (char), (size_t) offset_out, stdout);
209 column = offset_out = 0;
210 goto rescan;
211 }
212
213 line_out[offset_out++] = c;
214 }
215
216 saved_errno = errno;
217 if (!ferror (istream))
218 saved_errno = 0;
219
220 if (offset_out)
221 fwrite (line_out, sizeof (char), (size_t) offset_out, stdout);
222
223 if (STREQ (filename, "-"))
224 clearerr (istream);
225 else if (fclose (istream) != 0 && !saved_errno)
226 saved_errno = errno;
227
228 if (saved_errno)
229 {
230 error (0, saved_errno, "%s", quotef (filename));
231 return false;
232 }
233
234 return true;
235 }
236
237 int
238 main (int argc, char **argv)
239 {
240 size_t width = 80;
241 int i;
242 int optc;
243 bool ok;
244
245 initialize_main (&argc, &argv);
246 set_program_name (argv[0]);
247 setlocale (LC_ALL, "");
248 bindtextdomain (PACKAGE, LOCALEDIR);
249 textdomain (PACKAGE);
250
251 atexit (close_stdout);
252
253 break_spaces = count_bytes = have_read_stdin = false;
254
255 while ((optc = getopt_long (argc, argv, shortopts, longopts, nullptr)) != -1)
256 {
257 char optargbuf[2];
258
259 switch (optc)
260 {
261 case 'b': /* Count bytes rather than columns. */
262 count_bytes = true;
263 break;
264
265 case 's': /* Break at word boundaries. */
266 break_spaces = true;
267 break;
268
269 case '0': case '1': case '2': case '3': case '4':
270 case '5': case '6': case '7': case '8': case '9':
271 if (optarg)
272 optarg--;
273 else
274 {
275 optargbuf[0] = optc;
276 optargbuf[1] = '\0';
277 optarg = optargbuf;
278 }
279 FALLTHROUGH;
280 case 'w': /* Line width. */
281 width = xdectoumax (optarg, 1, SIZE_MAX - TAB_WIDTH - 1, "",
282 _("invalid number of columns"), 0);
283 break;
284
285 case_GETOPT_HELP_CHAR;
286
287 case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
288
289 default:
290 usage (EXIT_FAILURE);
291 }
292 }
293
294 if (argc == optind)
295 ok = fold_file ("-", width);
296 else
297 {
298 ok = true;
299 for (i = optind; i < argc; i++)
300 ok &= fold_file (argv[i], width);
301 }
302
303 if (have_read_stdin && fclose (stdin) == EOF)
304 error (EXIT_FAILURE, errno, "-");
305
306 return ok ? EXIT_SUCCESS : EXIT_FAILURE;
307 }