usr.bin/head/head.c

   1 /*
   2  * Copyright (c) 1980, 1987, 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#) Copyright (c) 1980, 1987, 1992, 1993 The Regents of the University of California.  All rights reserved.
  30  * @(#)head.c   8.2 (Berkeley) 5/4/95
  31  * $FreeBSD: src/usr.bin/head/head.c,v 1.10.2.1 2002/02/16 12:29:04 dwmalone Exp $
  32  * $DragonFly: src/usr.bin/head/head.c,v 1.6 2008/06/05 18:06:33 swildner Exp $
  33  */
  34
  35 #include <ctype.h>
  36 #include <err.h>
  37 #include <stdio.h>
  38 #include <stdlib.h>
  39 #include <string.h>
  40 #include <unistd.h>
  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 static void     head(FILE *, size_t);
  49 static void     head_bytes(FILE *, size_t);
  50 static void     obsolete(char *[]);
  51 static void     usage(void);
  52
  53 int
  54 main(int argc, char **argv)
  55 {
  56         int ch;
  57         FILE *fp;
  58         int first, linecnt = -1, bytecnt = -1, eval = 0;
  59         char *ep;
  60
  61         obsolete(argv);
  62         while ((ch = getopt(argc, argv, "n:c:")) != -1)
  63                 switch(ch) {
  64                 case 'c':
  65                         bytecnt = strtol(optarg, &ep, 10);
  66                         if (*ep != 0 || bytecnt <= 0)
  67                                 errx(1, "illegal byte count -- %s", optarg);
  68                         break;
  69                 case 'n':
  70                         linecnt = strtol(optarg, &ep, 10);
  71                         if (*ep != 0 || linecnt <= 0)
  72                                 errx(1, "illegal line count -- %s", optarg);
  73                         break;
  74                 default:
  75                         usage();
  76                 }
  77         argc -= optind;
  78         argv += optind;
  79
  80         if (linecnt != -1 && bytecnt != -1)
  81                 errx(1, "can't combine line and byte counts");
  82         if (linecnt == -1 )
  83                 linecnt = 10;
  84         if (*argv) {
  85                 for (first = 1; *argv; ++argv) {
  86                         if ((fp = fopen(*argv, "r")) == NULL) {
  87                                 warn("%s", *argv);
  88                                 eval = 1;
  89                                 continue;
  90                         }
  91                         if (argc > 1) {
  92                                 printf("%s==> %s <==\n",
  93                                     first ? "" : "\n", *argv);
  94                                 first = 0;
  95                         }
  96                         if (bytecnt == -1)
  97                                 head(fp, linecnt);
  98                         else
  99                                 head_bytes(fp, bytecnt);
 100                         fclose(fp);
 101                 }
 102         } else if (bytecnt == -1)
 103                 head(stdin, linecnt);
 104         else
 105                 head_bytes(stdin, bytecnt);
 106
 107         exit(eval);
 108 }
 109
 110 static void
 111 head(FILE *fp, size_t cnt)
 112 {
 113         char *cp;
 114         size_t error, readlen;
 115
 116         while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
 117                 error = fwrite(cp, sizeof(char), readlen, stdout);
 118                 if (error != readlen)
 119                         err(1, "stdout");
 120                 cnt--;
 121         }
 122 }
 123
 124 static void
 125 head_bytes(FILE *fp, size_t cnt)
 126 {
 127         char buf[4096];
 128         size_t readlen;
 129
 130         while (cnt) {
 131                 if (cnt < sizeof(buf))
 132                         readlen = cnt;
 133                 else
 134                         readlen = sizeof(buf);
 135                 readlen = fread(buf, sizeof(char), readlen, fp);
 136                 if (readlen == 0)
 137                         break;
 138                 if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
 139                         err(1, "stdout");
 140                 cnt -= readlen;
 141         }
 142 }
 143
 144 static void
 145 obsolete(char **argv)
 146 {
 147         char *ap;
 148
 149         while ((ap = *++argv)) {
 150                 /* Return if "--" or not "-[0-9]*". */
 151                 if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
 152                         return;
 153                 if ((ap = malloc(strlen(*argv) + 2)) == NULL)
 154                         err(1, "malloc failed");
 155                 ap[0] = '-';
 156                 ap[1] = 'n';
 157                 strcpy(ap + 2, *argv + 1);
 158                 *argv = ap;
 159         }
 160 }
 161
 162 static void
 163 usage(void)
 164 {
 165         fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
 166         exit(1);
 167 }