usr/src/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 are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#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      5.4 (Berkeley) %G%";
#endif /* not lint */

#include <stdio.h>
#include <ctype.h>
/*
 * 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;

        if (argc > 1 && argv[1][0] == '-') {
                if (!isdigit(argv[1][1])) {
                        fprintf(stderr, "head: illegal option -- %c\n", argv[1][1]);
                        goto usage;
                }
                if ((linecnt = atoi(argv[1] + 1)) < 0) {
usage:                  fputs("usage: head [-line_count] [file ...]\n", stderr);
                        exit(1);
                }
                --argc; ++argv;
        }
        /* setlinebuf(stdout); */
        for (firsttime = 1, --argc, ++argv;; 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*/
}