1 /* $OpenBSD: head.c,v 1.14 2007/10/31 16:29:50 jmc 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. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32 #ifndef lint 33 static const char copyright[] = 34 "@(#) Copyright (c) 1980, 1987 Regents of the University of California.\n\ 35 All rights reserved.\n"; 36 /*static char sccsid[] = "from: @(#)head.c 5.5 (Berkeley) 6/1/90";*/ 37 static const char rcsid[] = "$OpenBSD: head.c,v 1.14 2007/10/31 16:29:50 jmc Exp $"; 38 #endif /* not lint */ 39 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <ctype.h> 43 #include <limits.h> 44 #include <err.h> 45 #include <errno.h> 46 #include <unistd.h> 47 48 static void usage(void); 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 int 57 main(int argc, char *argv[]) 58 { 59 long cnt; 60 int ch, firsttime; 61 long linecnt = 10; 62 char *p = NULL; 63 64 /* handle obsolete -number syntax */ 65 if (argc > 1 && argv[1][0] == '-' && isdigit(argv[1][1])) { 66 p = argv[1] + 1; 67 argc--; 68 argv++; 69 } 70 71 while ((ch = getopt(argc, argv, "n:")) != -1) { 72 switch (ch) { 73 case 'n': 74 p = optarg; 75 break; 76 default: 77 usage(); 78 } 79 } 80 argc -= optind, argv += optind; 81 82 if (p) { 83 const char *errstr; 84 85 linecnt = strtonum(p, 1, LONG_MAX, &errstr); 86 if (errstr) 87 errx(1, "line count %s: %s", errstr, p); 88 } 89 90 /* setlinebuf(stdout); */ 91 for (firsttime = 1; ; firsttime = 0) { 92 if (!*argv) { 93 if (!firsttime) 94 exit(0); 95 } else { 96 if (!freopen(*argv, "r", stdin)) { 97 warn("%s", *argv++); 98 continue; 99 } 100 if (argc > 1) { 101 if (!firsttime) 102 putchar('\n'); 103 printf("==> %s <==\n", *argv); 104 } 105 ++argv; 106 } 107 for (cnt = linecnt; cnt && !feof(stdin); --cnt) 108 while ((ch = getchar()) != EOF) 109 if (putchar(ch) == '\n') 110 break; 111 } 112 /*NOTREACHED*/ 113 } 114 115 116 static void 117 usage(void) 118 { 119 fputs("usage: head [-count | -n count] [file ...]\n", stderr); 120 exit(1); 121 } 122