/usr.bin/head/head.c

  1/*
  2 * Copyright (c) 1980, 1987, 1992, 1993
  3 *	The Regents of the University of California.  All rights reserved.
  4 *
  5 * Redistribution and use in source and binary forms, with or without
  6 * modification, are permitted provided that the following conditions
  7 * are met:
  8 * 1. Redistributions of source code must retain the above copyright
  9 *    notice, this list of conditions and the following disclaimer.
 10 * 2. Redistributions in binary form must reproduce the above copyright
 11 *    notice, this list of conditions and the following disclaimer in the
 12 *    documentation and/or other materials provided with the distribution.
 13 * 4. Neither the name of the University nor the names of its contributors
 14 *    may be used to endorse or promote products derived from this software
 15 *    without specific prior written permission.
 16 *
 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 27 * SUCH DAMAGE.
 28 */
 29
 30#ifndef lint
 31static const char copyright[] =
 32"@(#) Copyright (c) 1980, 1987, 1992, 1993\n\
 33	The Regents of the University of California.  All rights reserved.\n";
 34#endif /* not lint */
 35
 36#ifndef lint
 37#if 0
 38static char sccsid[] = "@(#)head.c	8.2 (Berkeley) 5/4/95";
 39#endif
 40#endif /* not lint */
 41#include <sys/cdefs.h>
 42__FBSDID("$FreeBSD$");
 43
 44#include <sys/types.h>
 45
 46#include <ctype.h>
 47#include <err.h>
 48#include <inttypes.h>
 49#include <stdio.h>
 50#include <stdlib.h>
 51#include <string.h>
 52#include <unistd.h>
 53
 54/*
 55 * head - give the first few lines of a stream or of each of a set of files
 56 *
 57 * Bill Joy UCB August 24, 1977
 58 */
 59
 60static void head(FILE *, int);
 61static void head_bytes(FILE *, off_t);
 62static void obsolete(char *[]);
 63static void usage(void);
 64
 65int
 66main(int argc, char *argv[])
 67{
 68	int ch;
 69	FILE *fp;
 70	int first, linecnt = -1, eval = 0;
 71	off_t bytecnt = -1;
 72	char *ep;
 73
 74	obsolete(argv);
 75	while ((ch = getopt(argc, argv, "n:c:")) != -1)
 76		switch(ch) {
 77		case 'c':
 78			bytecnt = strtoimax(optarg, &ep, 10);
 79			if (*ep || bytecnt <= 0)
 80				errx(1, "illegal byte count -- %s", optarg);
 81			break;
 82		case 'n':
 83			linecnt = strtol(optarg, &ep, 10);
 84			if (*ep || linecnt <= 0)
 85				errx(1, "illegal line count -- %s", optarg);
 86			break;
 87		case '?':
 88		default:
 89			usage();
 90		}
 91	argc -= optind;
 92	argv += optind;
 93
 94	if (linecnt != -1 && bytecnt != -1)
 95		errx(1, "can't combine line and byte counts");
 96	if (linecnt == -1 )
 97		linecnt = 10;
 98	if (*argv) {
 99		for (first = 1; *argv; ++argv) {
100			if ((fp = fopen(*argv, "r")) == NULL) {
101				warn("%s", *argv);
102				eval = 1;
103				continue;
104			}
105			if (argc > 1) {
106				(void)printf("%s==> %s <==\n",
107				    first ? "" : "\n", *argv);
108				first = 0;
109			}
110			if (bytecnt == -1)
111				head(fp, linecnt);
112			else
113				head_bytes(fp, bytecnt);
114			(void)fclose(fp);
115		}
116	} else if (bytecnt == -1)
117		head(stdin, linecnt);
118	else
119		head_bytes(stdin, bytecnt);
120
121	exit(eval);
122}
123
124static void
125head(FILE *fp, int cnt)
126{
127	char *cp;
128	size_t error, readlen;
129
130	while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
131		error = fwrite(cp, sizeof(char), readlen, stdout);
132		if (error != readlen)
133			err(1, "stdout");
134		cnt--;
135	}
136}
137
138static void
139head_bytes(FILE *fp, off_t cnt)
140{
141	char buf[4096];
142	size_t readlen;
143
144	while (cnt) {
145		if ((uintmax_t)cnt < sizeof(buf))
146			readlen = cnt;
147		else
148			readlen = sizeof(buf);
149		readlen = fread(buf, sizeof(char), readlen, fp);
150		if (readlen == 0)
151			break;
152		if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
153			err(1, "stdout");
154		cnt -= readlen;
155	}
156}
157
158static void
159obsolete(char *argv[])
160{
161	char *ap;
162
163	while ((ap = *++argv)) {
164		/* Return if "--" or not "-[0-9]*". */
165		if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
166			return;
167		if ((ap = malloc(strlen(*argv) + 2)) == NULL)
168			err(1, NULL);
169		ap[0] = '-';
170		ap[1] = 'n';
171		(void)strcpy(ap + 2, *argv + 1);
172		*argv = ap;
173	}
174}
175
176static void
177usage(void)
178{
179
180	(void)fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
181	exit(1);
182}