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head.c revision 1.6 
      1 /*	$NetBSD: head.c,v 1.6 1997/01/09 20:19:50 tls Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1980, 1987 Regents of the University of California.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #ifndef lint
     37 char copyright[] =
     38 "@(#) Copyright (c) 1980, 1987 Regents of the University of California.\n\
     39  All rights reserved.\n";
     40 #endif /* not lint */
     41 
     42 #ifndef lint
     43 /*static char sccsid[] = "from: @(#)head.c	5.5 (Berkeley) 6/1/90";*/
     44 static char rcsid[] = "$NetBSD: head.c,v 1.6 1997/01/09 20:19:50 tls Exp $";
     45 #endif /* not lint */
     46 
     47 #include <stdio.h>
     48 #include <stdlib.h>
     49 #include <ctype.h>
     50 #include <unistd.h>
     51 
     52 static void usage ();
     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 
     60 int
     61 main(argc, argv)
     62 	int	argc;
     63 	char	**argv;
     64 {
     65 	register int	ch, cnt;
     66 	int	firsttime, linecnt = 10;
     67 
     68 	/* handle obsolete -number syntax */
     69 	if (argc > 1 && argv[1][0] == '-' && isdigit(argv[1][1])) {
     70 		if ((linecnt = atoi(argv[1] + 1)) < 0) {
     71 			usage ();
     72 		}
     73 		argc--; argv++;
     74 	}
     75 
     76 	while ((ch = getopt (argc, argv, "n:")) != EOF)
     77 		switch (ch) {
     78 		case 'n':
     79 			if ((linecnt = atoi(optarg)) < 0)
     80 				usage ();
     81 			break;
     82 
     83 		default:
     84 			usage();
     85 		}
     86 	argc -= optind, argv += optind;
     87 
     88 	/* setlinebuf(stdout); */
     89 	for (firsttime = 1; ; firsttime = 0) {
     90 		if (!*argv) {
     91 			if (!firsttime)
     92 				exit(0);
     93 		}
     94 		else {
     95 			if (!freopen(*argv, "r", stdin)) {
     96 				fprintf(stderr, "head: can't read %s.\n", *argv);
     97 				exit(1);
     98 			}
     99 			if (argc > 1) {
    100 				if (!firsttime)
    101 					putchar('\n');
    102 				printf("==> %s <==\n", *argv);
    103 			}
    104 			++argv;
    105 		}
    106 		for (cnt = linecnt; cnt; --cnt)
    107 			while ((ch = getchar()) != EOF)
    108 				if (putchar(ch) == '\n')
    109 					break;
    110 	}
    111 	/*NOTREACHED*/
    112 }
    113 
    114 
    115 static void
    116 usage ()
    117 {
    118 	fputs("usage: head [-n line_count] [file ...]\n", stderr);
    119 	exit(1);
    120 }
    121 
    122