1 /* $OpenBSD: head.c,v 1.18 2014/10/08 08:31:53 schwarze 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 FILE *fp; 52 long cnt; 53 int ch, firsttime; 54 long linecnt = 10; 55 char *p = NULL; 56 int status = 0; 57 58 /* handle obsolete -number syntax */ 59 if (argc > 1 && argv[1][0] == '-' && 60 isdigit((unsigned char)argv[1][1])) { 61 p = argv[1] + 1; 62 argc--; 63 argv++; 64 } 65 66 while ((ch = getopt(argc, argv, "n:")) != -1) { 67 switch (ch) { 68 case 'n': 69 p = optarg; 70 break; 71 default: 72 usage(); 73 } 74 } 75 argc -= optind, argv += optind; 76 77 if (p) { 78 const char *errstr; 79 80 linecnt = strtonum(p, 1, LONG_MAX, &errstr); 81 if (errstr) 82 errx(1, "line count %s: %s", errstr, p); 83 } 84 85 for (firsttime = 1; ; firsttime = 0) { 86 if (!*argv) { 87 if (!firsttime) 88 exit(status); 89 fp = stdin; 90 } else { 91 if ((fp = fopen(*argv, "r")) == NULL) { 92 warn("%s", *argv++); 93 status = 1; 94 continue; 95 } 96 if (argc > 1) { 97 if (!firsttime) 98 putchar('\n'); 99 printf("==> %s <==\n", *argv); 100 } 101 ++argv; 102 } 103 for (cnt = linecnt; cnt && !feof(fp); --cnt) 104 while ((ch = getc(fp)) != EOF) 105 if (putchar(ch) == '\n') 106 break; 107 fclose(fp); 108 } 109 /*NOTREACHED*/ 110 } 111 112 113 static void 114 usage(void) 115 { 116 fputs("usage: head [-count | -n count] [file ...]\n", stderr); 117 exit(1); 118 } 119