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head.c revision 1.4 
      1 /*
      2  * Copyright (c) 1980, 1987 Regents of the University of California.
      3  * 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  * 3. All advertising materials mentioning features or use of this software
     14  *    must display the following acknowledgement:
     15  *	This product includes software developed by the University of
     16  *	California, Berkeley and its contributors.
     17  * 4. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #ifndef lint
     35 char copyright[] =
     36 "@(#) Copyright (c) 1980, 1987 Regents of the University of California.\n\
     37  All rights reserved.\n";
     38 #endif /* not lint */
     39 
     40 #ifndef lint
     41 /*static char sccsid[] = "from: @(#)head.c	5.5 (Berkeley) 6/1/90";*/
     42 static char rcsid[] = "$Id: head.c,v 1.4 1993/08/27 22:30:27 jtc Exp $";
     43 #endif /* not lint */
     44 
     45 #include <stdio.h>
     46 #include <stdlib.h>
     47 #include <ctype.h>
     48 
     49 static void usage ();
     50 
     51 /*
     52  * head - give the first few lines of a stream or of each of a set of files
     53  *
     54  * Bill Joy UCB August 24, 1977
     55  */
     56 
     57 int
     58 main(argc, argv)
     59 	int	argc;
     60 	char	**argv;
     61 {
     62 	register int	ch, cnt;
     63 	int	firsttime, linecnt = 10;
     64 
     65 	/* handle obsolete -number syntax */
     66 	if (argc > 1 && argv[1][0] == '-' && isdigit(argv[1][1])) {
     67 		if ((linecnt = atoi(argv[1] + 1)) < 0) {
     68 			usage ();
     69 		}
     70 		argc--; argv++;
     71 	}
     72 
     73 	while ((ch = getopt (argc, argv, "n:")) != EOF)
     74 		switch (ch) {
     75 		case 'n':
     76 			if ((linecnt = atoi(optarg)) < 0)
     77 				usage ();
     78 			break;
     79 
     80 		default:
     81 			usage();
     82 		}
     83 	argc -= optind, argv += optind;
     84 
     85 	/* setlinebuf(stdout); */
     86 	for (firsttime = 1; ; firsttime = 0) {
     87 		if (!*argv) {
     88 			if (!firsttime)
     89 				exit(0);
     90 		}
     91 		else {
     92 			if (!freopen(*argv, "r", stdin)) {
     93 				fprintf(stderr, "head: can't read %s.\n", *argv);
     94 				exit(1);
     95 			}
     96 			if (argc > 1) {
     97 				if (!firsttime)
     98 					putchar('\n');
     99 				printf("==> %s <==\n", *argv);
    100 			}
    101 			++argv;
    102 		}
    103 		for (cnt = linecnt; cnt; --cnt)
    104 			while ((ch = getchar()) != EOF)
    105 				if (putchar(ch) == '\n')
    106 					break;
    107 	}
    108 	/*NOTREACHED*/
    109 }
    110 
    111 
    112 static void
    113 usage ()
    114 {
    115 	fputs("usage: head [-n line_count] [file ...]\n", stderr);
    116 	exit(1);
    117 }
    118 
    119