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/* $OpenBSD: head.c,v 1.19 2015/10/07 06:55:10 deraadt Exp $ */
/*
* Copyright (c) 1980, 1987 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <limits.h>
#include <err.h>
#include <errno.h>
#include <unistd.h>
static void usage(void);
/*
* head - give the first few lines of a stream or of each of a set of files
*
* Bill Joy UCB August 24, 1977
*/
int
main(int argc, char *argv[])
{
FILE *fp;
long cnt;
int ch, firsttime;
long linecnt = 10;
char *p = NULL;
int status = 0;
if (tame("stdio rpath", NULL) == -1)
err(1, "tame");
/* handle obsolete -number syntax */
if (argc > 1 && argv[1][0] == '-' &&
isdigit((unsigned char)argv[1][1])) {
p = argv[1] + 1;
argc--;
argv++;
}
while ((ch = getopt(argc, argv, "n:")) != -1) {
switch (ch) {
case 'n':
p = optarg;
break;
default:
usage();
}
}
argc -= optind, argv += optind;
if (p) {
const char *errstr;
linecnt = strtonum(p, 1, LONG_MAX, &errstr);
if (errstr)
errx(1, "line count %s: %s", errstr, p);
}
for (firsttime = 1; ; firsttime = 0) {
if (!*argv) {
if (!firsttime)
exit(status);
fp = stdin;
if (tame("stdio", NULL) == -1)
err(1, "tame");
} else {
if ((fp = fopen(*argv, "r")) == NULL) {
warn("%s", *argv++);
status = 1;
continue;
}
if (argc > 1) {
if (!firsttime)
putchar('\n');
printf("==> %s <==\n", *argv);
}
++argv;
}
for (cnt = linecnt; cnt && !feof(fp); --cnt)
while ((ch = getc(fp)) != EOF)
if (putchar(ch) == '\n')
break;
fclose(fp);
}
/*NOTREACHED*/
}
static void
usage(void)
{
fputs("usage: head [-count | -n count] [file ...]\n", stderr);
exit(1);
}
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