usr.bin/head/head.c

/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 */

#ifndef lint
char copyright[] =
"@(#) Copyright (c) 1980, 1987 Regents of the University of California.\n\
 All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)head.c      5.5 (Berkeley) 6/1/90";
#endif /* not lint */

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

static void usage ();

/*
 * head - give the first few lines of a stream or of each of a set of files
 *
 * Bill Joy UCB August 24, 1977
 */

main(argc, argv)
        int     argc;
        char    **argv;
{
        register int    ch, cnt;
        int     firsttime, linecnt = 10;

        /* handle obsolete -number syntax */
        if (argc > 1 && argv[1][0] == '-' && isdigit(argv[1][1])) {
                if ((linecnt = atoi(argv[1] + 1)) < 0) {
                        usage ();
                }
                argc--; argv++;
        }

        while ((ch = getopt (argc, argv, "n:")) != EOF)
                switch (ch) {
                case 'n':
                        if ((linecnt = atoi(optarg)) < 0)
                                usage ();
                        break;

                default:
                        usage();
                }
        argc -= optind, argv += optind;

        /* setlinebuf(stdout); */
        for (firsttime = 1; ; firsttime = 0) {
                if (!*argv) {
                        if (!firsttime)
                                exit(0);
                }
                else {
                        if (!freopen(*argv, "r", stdin)) {
                                fprintf(stderr, "head: can't read %s.\n", *argv);
                                exit(1);
                        }
                        if (argc > 1) {
                                if (!firsttime)
                                        putchar('\n');
                                printf("==> %s <==\n", *argv);
                        }
                        ++argv;
                }
                for (cnt = linecnt; cnt; --cnt)
                        while ((ch = getchar()) != EOF)
                                if (putchar(ch) == '\n')
                                        break;
        }
        /*NOTREACHED*/
}


static void
usage ()
{
        fputs("usage: head [-n line_count] [file ...]\n", stderr);
        exit(1);
}