1 /* head -- output first part of file(s)
2 Copyright (C) 89, 90, 91, 1995-2001 Free Software Foundation, Inc.
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 2, or (at your option)
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.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software Foundation,
16 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
18 /* Options: (see usage)
19 Reads from standard input if no files are given or when a filename of
21 By default, filename headers are printed only if more than one file
23 By default, prints the first 10 lines (head -n 10).
25 David MacKenzie <djm@gnu.ai.mit.edu> */
31 #include <sys/types.h>
36 #include "safe-read.h"
38 /* The official name of this program (e.g., no `g' prefix). */
39 #define PROGRAM_NAME "head"
41 #define AUTHORS "David MacKenzie"
43 /* Number of lines/chars/blocks to head. */
44 #define DEFAULT_NUMBER 10
46 /* Size of atomic reads. */
47 #define BUFSIZE (512 * 8)
49 /* If nonzero, print filename headers. */
50 static int print_headers;
52 /* When to print the filename banners. */
55 multiple_files, always, never
58 /* The name this program was run with. */
61 /* Have we ever read standard input? */
62 static int have_read_stdin;
64 static struct option const long_options[] =
66 {"bytes", required_argument, NULL, 'c'},
67 {"lines", required_argument, NULL, 'n'},
68 {"quiet", no_argument, NULL, 'q'},
69 {"silent", no_argument, NULL, 'q'},
70 {"verbose", no_argument, NULL, 'v'},
71 {GETOPT_HELP_OPTION_DECL},
72 {GETOPT_VERSION_OPTION_DECL},
80 fprintf (stderr, _("Try `%s --help' for more information.\n"),
85 Usage: %s [OPTION]... [FILE]...\n\
89 Print first 10 lines of each FILE to standard output.\n\
90 With more than one FILE, precede each with a header giving the file name.\n\
91 With no FILE, or when FILE is -, read standard input.\n\
93 Mandatory arguments to long options are mandatory for short options too.\n\
94 -c, --bytes=SIZE print first SIZE bytes\n\
95 -n, --lines=NUMBER print first NUMBER lines instead of first 10\n\
98 -q, --quiet, --silent never print headers giving file names\n\
99 -v, --verbose always print headers giving file names\n\
100 --help display this help and exit\n\
101 --version output version information and exit\n\
103 SIZE may have a multiplier suffix: b for 512, k for 1K, m for 1 Meg.\n\
104 If -VALUE is used as first OPTION, read -c VALUE when one of\n\
105 multipliers bkm follows concatenated, else read -n VALUE.\n\
107 puts (_("\nReport bugs to <bug-textutils@gnu.org>."));
109 exit (status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
113 write_header (const char *filename)
115 static int first_file = 1;
117 printf ("%s==> %s <==\n", (first_file ? "" : "\n"), filename);
122 head_bytes (const char *filename, int fd, uintmax_t bytes_to_write)
124 char buffer[BUFSIZE];
126 size_t bytes_to_read = BUFSIZE;
128 /* Need BINARY I/O for the byte counts to be accurate. */
129 SET_BINARY2 (fd, fileno (stdout));
131 while (bytes_to_write)
133 if (bytes_to_write < bytes_to_read)
134 bytes_to_read = bytes_to_write;
135 bytes_read = safe_read (fd, buffer, bytes_to_read);
138 error (0, errno, "%s", filename);
143 if (fwrite (buffer, 1, bytes_read, stdout) == 0)
144 error (EXIT_FAILURE, errno, _("write error"));
145 bytes_to_write -= bytes_read;
151 head_lines (const char *filename, int fd, uintmax_t lines_to_write)
153 char buffer[BUFSIZE];
155 /* Need BINARY I/O for the byte counts to be accurate. */
156 SET_BINARY2 (fd, fileno (stdout));
158 while (lines_to_write)
160 int bytes_read = safe_read (fd, buffer, BUFSIZE);
161 int bytes_to_write = 0;
165 error (0, errno, "%s", filename);
170 while (bytes_to_write < bytes_read)
171 if (buffer[bytes_to_write++] == '\n' && --lines_to_write == 0)
173 if (fwrite (buffer, 1, bytes_to_write, stdout) == 0)
174 error (EXIT_FAILURE, errno, _("write error"));
180 head (const char *filename, int fd, uintmax_t n_units, int count_lines)
183 write_header (filename);
186 return head_lines (filename, fd, n_units);
188 return head_bytes (filename, fd, n_units);
192 head_file (const char *filename, uintmax_t n_units, int count_lines)
196 if (STREQ (filename, "-"))
199 return head (_("standard input"), STDIN_FILENO, n_units, count_lines);
203 fd = open (filename, O_RDONLY);
208 errors = head (filename, fd, n_units, count_lines);
212 error (0, errno, "%s", filename);
217 /* Convert a string of decimal digits, N_STRING, with a single, optional suffix
218 character (b, k, or m) to an integral value. Upon successful conversion,
219 return that value. If it cannot be converted, give a diagnostic and exit.
220 COUNT_LINES indicates whether N_STRING is a number of bytes or a number
221 of lines. It is used solely to give a more specific diagnostic. */
224 string_to_integer (int count_lines, const char *n_string)
229 s_err = xstrtoumax (n_string, NULL, 10, &n, "bkm");
231 if (s_err == LONGINT_OVERFLOW)
233 error (EXIT_FAILURE, 0,
234 _("%s: %s is so large that it is not representable"), n_string,
235 count_lines ? _("number of lines") : _("number of bytes"));
238 if (s_err != LONGINT_OK)
240 error (EXIT_FAILURE, 0, "%s: %s", n_string,
242 ? _("invalid number of lines")
243 : _("invalid number of bytes")));
250 main (int argc, char **argv)
252 enum header_mode header_mode = multiple_files;
257 /* Number of items to print. */
258 uintmax_t n_units = DEFAULT_NUMBER;
260 /* If nonzero, interpret the numeric argument as the number of lines.
261 Otherwise, interpret it as the number of bytes. */
264 program_name = argv[0];
265 setlocale (LC_ALL, "");
266 bindtextdomain (PACKAGE, LOCALEDIR);
267 textdomain (PACKAGE);
269 atexit (close_stdout);
275 if (argc > 1 && argv[1][0] == '-' && ISDIGIT (argv[1][1]))
278 char multiplier_char = 0;
280 n_string = &argv[1][1];
282 /* Old option syntax; a dash, one or more digits, and one or
283 more option letters. Move past the number. */
284 for (++argv[1]; ISDIGIT (*argv[1]); ++argv[1])
289 /* Pointer to the byte after the last digit. */
290 end_n_string = argv[1];
292 /* Parse any appended option letters. */
306 multiplier_char = *argv[1];
318 header_mode = always;
322 error (0, 0, _("unrecognized option `-%c'"), *argv[1]);
328 /* Append the multiplier character (if any) onto the end of
329 the digit string. Then add NUL byte if necessary. */
330 *end_n_string = multiplier_char;
332 *(++end_n_string) = 0;
334 n_units = string_to_integer (count_lines, n_string);
336 /* Make the options we just parsed invisible to getopt. */
341 /* FIXME: allow POSIX options if there were obsolescent ones? */
345 while ((c = getopt_long (argc, argv, "c:n:qv", long_options, NULL)) != -1)
354 n_units = string_to_integer (count_lines, optarg);
359 n_units = string_to_integer (count_lines, optarg);
367 header_mode = always;
370 case_GETOPT_HELP_CHAR;
372 case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
379 if (header_mode == always
380 || (header_mode == multiple_files && optind < argc - 1))
384 exit_status |= head_file ("-", n_units, count_lines);
386 for (; optind < argc; ++optind)
387 exit_status |= head_file (argv[optind], n_units, count_lines);
389 if (have_read_stdin && close (STDIN_FILENO) < 0)
390 error (EXIT_FAILURE, errno, "-");
392 exit (exit_status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);