1 /* head -- output first part of file(s)
2 Copyright (C) 1989, 1990, 1991, 1995 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
16 Foundation, 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>
35 /* Number of lines/chars/blocks to head. */
36 #define DEFAULT_NUMBER 10
38 /* Size of atomic reads. */
39 #define BUFSIZE (512 * 8)
41 /* Number of bytes per item we are printing.
42 If 0, head in lines. */
45 /* If nonzero, print filename headers. */
46 static int print_headers;
48 /* When to print the filename banners. */
51 multiple_files, always, never
56 /* The name this program was run with. */
59 /* Have we ever read standard input? */
60 static int have_read_stdin;
62 /* If nonzero, display usage information and exit. */
65 /* If nonzero, print the version on standard output then exit. */
66 static int show_version;
68 static struct option const long_options[] =
70 {"bytes", required_argument, NULL, 'c'},
71 {"lines", required_argument, NULL, 'n'},
72 {"quiet", no_argument, NULL, 'q'},
73 {"silent", no_argument, NULL, 'q'},
74 {"verbose", no_argument, NULL, 'v'},
75 {"help", no_argument, &show_help, 1},
76 {"version", no_argument, &show_version, 1},
84 fprintf (stderr, _("Try `%s --help' for more information.\n"),
89 Usage: %s [OPTION]... [FILE]...\n\
93 Print first 10 lines of each FILE to standard output.\n\
94 With more than one FILE, precede each with a header giving the file name.\n\
95 With no FILE, or when FILE is -, read standard input.\n\
97 -c, --bytes=SIZE print first SIZE bytes\n\
98 -n, --lines=NUMBER print first NUMBER lines instead of first 10\n\
99 -q, --quiet, --silent never print headers giving file names\n\
100 -v, --verbose always print headers giving file names\n\
101 --help display this help and exit\n\
102 --version output version information and exit\n\
104 SIZE may have a multiplier suffix: b for 512, k for 1K, m for 1 Meg.\n\
105 If -VALUE is used as first OPTION, read -c VALUE when one of\n\
106 multipliers bkm follows concatenated, else read -n VALUE.\n\
112 /* Convert STR, a string of ASCII digits, into an unsigned integer.
113 Return -1 if STR does not represent a valid unsigned integer. */
116 atou (const char *str)
120 for (value = 0; ISDIGIT (*str); ++str)
121 value = value * 10 + *str - '0';
122 return *str ? -1 : value;
126 parse_unit (char *str)
128 int arglen = strlen (str);
133 switch (str[arglen - 1])
137 str[arglen - 1] = '\0';
141 str[arglen - 1] = '\0';
145 str[arglen - 1] = '\0';
151 write_header (const char *filename)
153 static int first_file = 1;
155 printf ("%s==> %s <==\n", (first_file ? "" : "\n"), filename);
160 head_bytes (const char *filename, int fd, long int bytes_to_write)
162 char buffer[BUFSIZE];
165 while (bytes_to_write)
167 bytes_read = safe_read (fd, buffer, BUFSIZE);
170 error (0, errno, "%s", filename);
175 if (bytes_read > bytes_to_write)
176 bytes_read = bytes_to_write;
177 if (fwrite (buffer, 1, bytes_read, stdout) == 0)
178 error (1, errno, _("write error"));
179 bytes_to_write -= bytes_read;
185 head_lines (const char *filename, int fd, long int lines_to_write)
187 char buffer[BUFSIZE];
191 while (lines_to_write)
193 bytes_read = safe_read (fd, buffer, BUFSIZE);
196 error (0, errno, "%s", filename);
202 while (bytes_to_write < bytes_read)
203 if (buffer[bytes_to_write++] == '\n' && --lines_to_write == 0)
205 if (fwrite (buffer, 1, bytes_to_write, stdout) == 0)
206 error (1, errno, _("write error"));
212 head (const char *filename, int fd, long int number)
215 return head_bytes (filename, fd, number);
217 return head_lines (filename, fd, number);
221 head_file (const char *filename, long int number)
225 if (!strcmp (filename, "-"))
228 filename = _("standard input");
230 write_header (filename);
231 return head (filename, 0, number);
235 fd = open (filename, O_RDONLY);
241 write_header (filename);
242 errors = head (filename, fd, number);
246 error (0, errno, "%s", filename);
252 main (int argc, char **argv)
254 enum header_mode header_mode = multiple_files;
256 long number = -1; /* Number of items to print (-1 if undef.). */
257 int c; /* Option character. */
259 program_name = argv[0];
260 setlocale (LC_ALL, "");
261 bindtextdomain (PACKAGE, LOCALEDIR);
262 textdomain (PACKAGE);
268 if (argc > 1 && argv[1][0] == '-' && ISDIGIT (argv[1][1]))
270 /* Old option syntax; a dash, one or more digits, and one or
271 more option letters. Move past the number. */
272 for (number = 0, ++argv[1]; ISDIGIT (*argv[1]); ++argv[1])
273 number = number * 10 + *argv[1] - '0';
274 /* Parse any appended option letters. */
304 header_mode = always;
308 error (0, 0, _("unrecognized option `-%c'"), *argv[1]);
313 /* Make the options we just parsed invisible to getopt. */
319 while ((c = getopt_long (argc, argv, "c:n:qv", long_options, (int *) 0))
334 /* FIXME: use xstrtoul instead. */
335 number = atou (optarg);
337 error (1, 0, _("invalid number `%s'"), optarg);
345 header_mode = always;
355 printf ("head - %s\n", PACKAGE_VERSION);
363 number = DEFAULT_NUMBER;
368 if (header_mode == always
369 || (header_mode == multiple_files && optind < argc - 1))
373 exit_status |= head_file ("-", number);
375 for (; optind < argc; ++optind)
376 exit_status |= head_file (argv[optind], number);
378 if (have_read_stdin && close (0) < 0)
379 error (1, errno, "-");
380 if (fclose (stdout) == EOF)
381 error (1, errno, _("write error"));