Home | History | Annotate | Line # | Download | only in head
head.c revision 1.5 
      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 1.5 1993/10/13 18:34:17 jtc Exp $";
     43 #endif /* not lint */
     44 
     45 #include <stdio.h>
     46 #include <stdlib.h>
     47 #include <ctype.h>
     48 #include <unistd.h>
     49 
     50 static void usage ();
     51 
     52 /*
     53  * head - give the first few lines of a stream or of each of a set of files
     54  *
     55  * Bill Joy UCB August 24, 1977
     56  */
     57 
     58 int
     59 main(argc, argv)
     60 	int	argc;
     61 	char	**argv;
     62 {
     63 	register int	ch, cnt;
     64 	int	firsttime, linecnt = 10;
     65 
     66 	/* handle obsolete -number syntax */
     67 	if (argc > 1 && argv[1][0] == '-' && isdigit(argv[1][1])) {
     68 		if ((linecnt = atoi(argv[1] + 1)) < 0) {
     69 			usage ();
     70 		}
     71 		argc--; argv++;
     72 	}
     73 
     74 	while ((ch = getopt (argc, argv, "n:")) != EOF)
     75 		switch (ch) {
     76 		case 'n':
     77 			if ((linecnt = atoi(optarg)) < 0)
     78 				usage ();
     79 			break;
     80 
     81 		default:
     82 			usage();
     83 		}
     84 	argc -= optind, argv += optind;
     85 
     86 	/* setlinebuf(stdout); */
     87 	for (firsttime = 1; ; firsttime = 0) {
     88 		if (!*argv) {
     89 			if (!firsttime)
     90 				exit(0);
     91 		}
     92 		else {
     93 			if (!freopen(*argv, "r", stdin)) {
     94 				fprintf(stderr, "head: can't read %s.\n", *argv);
     95 				exit(1);
     96 			}
     97 			if (argc > 1) {
     98 				if (!firsttime)
     99 					putchar('\n');
    100 				printf("==> %s <==\n", *argv);
    101 			}
    102 			++argv;
    103 		}
    104 		for (cnt = linecnt; cnt; --cnt)
    105 			while ((ch = getchar()) != EOF)
    106 				if (putchar(ch) == '\n')
    107 					break;
    108 	}
    109 	/*NOTREACHED*/
    110 }
    111 
    112 
    113 static void
    114 usage ()
    115 {
    116 	fputs("usage: head [-n line_count] [file ...]\n", stderr);
    117 	exit(1);
    118 }
    119 
    120