1 /* $OpenBSD: head.c,v 1.22 2021/10/10 15:57:25 cheloha 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 const char *errstr; 52 FILE *fp; 53 long cnt; 54 int ch, firsttime; 55 long linecnt = 10; 56 int status = 0; 57 58 if (pledge("stdio rpath", NULL) == -1) 59 err(1, "pledge"); 60 61 /* handle obsolete -number syntax */ 62 if (argc > 1 && argv[1][0] == '-' && 63 isdigit((unsigned char)argv[1][1])) { 64 linecnt = strtonum(argv[1] + 1, 1, LONG_MAX, &errstr); 65 if (errstr != NULL) 66 errx(1, "count is %s: %s", errstr, argv[1] + 1); 67 argc--; 68 argv++; 69 } 70 71 while ((ch = getopt(argc, argv, "n:")) != -1) { 72 switch (ch) { 73 case 'n': 74 linecnt = strtonum(optarg, 1, LONG_MAX, &errstr); 75 if (errstr != NULL) 76 errx(1, "count is %s: %s", errstr, optarg); 77 break; 78 default: 79 usage(); 80 } 81 } 82 argc -= optind, argv += optind; 83 84 for (firsttime = 1; ; firsttime = 0) { 85 if (!*argv) { 86 if (!firsttime) 87 exit(status); 88 fp = stdin; 89 if (pledge("stdio", NULL) == -1) 90 err(1, "pledge"); 91 } else { 92 if ((fp = fopen(*argv, "r")) == NULL) { 93 warn("%s", *argv++); 94 status = 1; 95 continue; 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 && !feof(fp); --cnt) 105 while ((ch = getc(fp)) != EOF) 106 if (putchar(ch) == '\n') 107 break; 108 fclose(fp); 109 } 110 /*NOTREACHED*/ 111 } 112 113 114 static void 115 usage(void) 116 { 117 fputs("usage: head [-count | -n count] [file ...]\n", stderr); 118 exit(1); 119 } 120