1 /* $OpenBSD: head.c,v 1.15 2009/10/27 23:59:38 deraadt 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 #include <stdio.h> 33 #include <stdlib.h> 34 #include <ctype.h> 35 #include <limits.h> 36 #include <err.h> 37 #include <errno.h> 38 #include <unistd.h> 39 40 static void usage(void); 41 42 /* 43 * head - give the first few lines of a stream or of each of a set of files 44 * 45 * Bill Joy UCB August 24, 1977 46 */ 47 48 int 49 main(int argc, char *argv[]) 50 { 51 long cnt; 52 int ch, firsttime; 53 long linecnt = 10; 54 char *p = NULL; 55 56 /* handle obsolete -number syntax */ 57 if (argc > 1 && argv[1][0] == '-' && isdigit(argv[1][1])) { 58 p = argv[1] + 1; 59 argc--; 60 argv++; 61 } 62 63 while ((ch = getopt(argc, argv, "n:")) != -1) { 64 switch (ch) { 65 case 'n': 66 p = optarg; 67 break; 68 default: 69 usage(); 70 } 71 } 72 argc -= optind, argv += optind; 73 74 if (p) { 75 const char *errstr; 76 77 linecnt = strtonum(p, 1, LONG_MAX, &errstr); 78 if (errstr) 79 errx(1, "line count %s: %s", errstr, p); 80 } 81 82 /* setlinebuf(stdout); */ 83 for (firsttime = 1; ; firsttime = 0) { 84 if (!*argv) { 85 if (!firsttime) 86 exit(0); 87 } else { 88 if (!freopen(*argv, "r", stdin)) { 89 warn("%s", *argv++); 90 continue; 91 } 92 if (argc > 1) { 93 if (!firsttime) 94 putchar('\n'); 95 printf("==> %s <==\n", *argv); 96 } 97 ++argv; 98 } 99 for (cnt = linecnt; cnt && !feof(stdin); --cnt) 100 while ((ch = getchar()) != EOF) 101 if (putchar(ch) == '\n') 102 break; 103 } 104 /*NOTREACHED*/ 105 } 106 107 108 static void 109 usage(void) 110 { 111 fputs("usage: head [-count | -n count] [file ...]\n", stderr); 112 exit(1); 113 } 114