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head.c revision 1.2 
      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[] = "@(#)head.c	5.5 (Berkeley) 6/1/90";
     42 #endif /* not lint */
     43 
     44 #include <stdio.h>
     45 #include <stdlib.h>
     46 #include <ctype.h>
     47 
     48 static void usage ();
     49 
     50 /*
     51  * head - give the first few lines of a stream or of each of a set of files
     52  *
     53  * Bill Joy UCB August 24, 1977
     54  */
     55 
     56 main(argc, argv)
     57 	int	argc;
     58 	char	**argv;
     59 {
     60 	register int	ch, cnt;
     61 	int	firsttime, linecnt = 10;
     62 
     63 	/* handle obsolete -number syntax */
     64 	if (argc > 1 && argv[1][0] == '-' && isdigit(argv[1][1])) {
     65 		if ((linecnt = atoi(argv[1] + 1)) < 0) {
     66 			usage ();
     67 		}
     68 		argc--; argv++;
     69 	}
     70 
     71 	while ((ch = getopt (argc, argv, "n:")) != EOF)
     72 		switch (ch) {
     73 		case 'n':
     74 			if ((linecnt = atoi(optarg)) < 0)
     75 				usage ();
     76 			break;
     77 
     78 		default:
     79 			usage();
     80 		}
     81 	argc -= optind, argv += optind;
     82 
     83 	/* setlinebuf(stdout); */
     84 	for (firsttime = 1; ; firsttime = 0) {
     85 		if (!*argv) {
     86 			if (!firsttime)
     87 				exit(0);
     88 		}
     89 		else {
     90 			if (!freopen(*argv, "r", stdin)) {
     91 				fprintf(stderr, "head: can't read %s.\n", *argv);
     92 				exit(1);
     93 			}
     94 			if (argc > 1) {
     95 				if (!firsttime)
     96 					putchar('\n');
     97 				printf("==> %s <==\n", *argv);
     98 			}
     99 			++argv;
    100 		}
    101 		for (cnt = linecnt; cnt; --cnt)
    102 			while ((ch = getchar()) != EOF)
    103 				if (putchar(ch) == '\n')
    104 					break;
    105 	}
    106 	/*NOTREACHED*/
    107 }
    108 
    109 
    110 static void
    111 usage ()
    112 {
    113 	fputs("usage: head [-n line_count] [file ...]\n", stderr);
    114 	exit(1);
    115 }
    116 
    117