1 /* $OpenBSD: head.c,v 1.16 2013/11/26 13:21:17 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] == '-' && 58 isdigit((unsigned char)argv[1][1])) { 59 p = argv[1] + 1; 60 argc--; 61 argv++; 62 } 63 64 while ((ch = getopt(argc, argv, "n:")) != -1) { 65 switch (ch) { 66 case 'n': 67 p = optarg; 68 break; 69 default: 70 usage(); 71 } 72 } 73 argc -= optind, argv += optind; 74 75 if (p) { 76 const char *errstr; 77 78 linecnt = strtonum(p, 1, LONG_MAX, &errstr); 79 if (errstr) 80 errx(1, "line count %s: %s", errstr, p); 81 } 82 83 /* setlinebuf(stdout); */ 84 for (firsttime = 1; ; firsttime = 0) { 85 if (!*argv) { 86 if (!firsttime) 87 exit(0); 88 } else { 89 if (!freopen(*argv, "r", stdin)) { 90 warn("%s", *argv++); 91 continue; 92 } 93 if (argc > 1) { 94 if (!firsttime) 95 putchar('\n'); 96 printf("==> %s <==\n", *argv); 97 } 98 ++argv; 99 } 100 for (cnt = linecnt; cnt && !feof(stdin); --cnt) 101 while ((ch = getchar()) != EOF) 102 if (putchar(ch) == '\n') 103 break; 104 } 105 /*NOTREACHED*/ 106 } 107 108 109 static void 110 usage(void) 111 { 112 fputs("usage: head [-count | -n count] [file ...]\n", stderr); 113 exit(1); 114 } 115