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. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#) Copyright (c) 1980, 1987, 1992, 1993 The Regents of the University of California.  All rights reserved.
  34  * @(#)head.c   8.2 (Berkeley) 5/4/95
  35  * $FreeBSD: src/usr.bin/head/head.c,v 1.10.2.1 2002/02/16 12:29:04 dwmalone Exp $
  36  * $DragonFly: src/usr.bin/head/head.c,v 1.5 2005/03/12 11:10:02 liamfoy Exp $
  37  */
  38
  39 #include <ctype.h>
  40 #include <err.h>
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <unistd.h>
  45
  46 /*
  47  * head - give the first few lines of a stream or of each of a set of files
  48  *
  49  * Bill Joy UCB August 24, 1977
  50  */
  51
  52 static void     head(FILE *, size_t);
  53 static void     head_bytes(FILE *, size_t);
  54 static void     obsolete(char *[]);
  55 static void     usage(void);
  56
  57 int
  58 main(int argc, char **argv)
  59 {
  60         int ch;
  61         FILE *fp;
  62         int first, linecnt = -1, bytecnt = -1, eval = 0;
  63         char *ep;
  64
  65         obsolete(argv);
  66         while ((ch = getopt(argc, argv, "n:c:")) != -1)
  67                 switch(ch) {
  68                 case 'c':
  69                         bytecnt = strtol(optarg, &ep, 10);
  70                         if (*ep != NULL || bytecnt <= 0)
  71                                 errx(1, "illegal byte count -- %s", optarg);
  72                         break;
  73                 case 'n':
  74                         linecnt = strtol(optarg, &ep, 10);
  75                         if (*ep != NULL || linecnt <= 0)
  76                                 errx(1, "illegal line count -- %s", optarg);
  77                         break;
  78                 default:
  79                         usage();
  80                 }
  81         argc -= optind;
  82         argv += optind;
  83
  84         if (linecnt != -1 && bytecnt != -1)
  85                 errx(1, "can't combine line and byte counts");
  86         if (linecnt == -1 )
  87                 linecnt = 10;
  88         if (*argv) {
  89                 for (first = 1; *argv; ++argv) {
  90                         if ((fp = fopen(*argv, "r")) == NULL) {
  91                                 warn("%s", *argv);
  92                                 eval = 1;
  93                                 continue;
  94                         }
  95                         if (argc > 1) {
  96                                 printf("%s==> %s <==\n",
  97                                     first ? "" : "\n", *argv);
  98                                 first = 0;
  99                         }
 100                         if (bytecnt == -1)
 101                                 head(fp, linecnt);
 102                         else
 103                                 head_bytes(fp, bytecnt);
 104                         fclose(fp);
 105                 }
 106         } else if (bytecnt == -1)
 107                 head(stdin, linecnt);
 108         else
 109                 head_bytes(stdin, bytecnt);
 110
 111         exit(eval);
 112 }
 113
 114 static void
 115 head(FILE *fp, size_t cnt)
 116 {
 117         char *cp;
 118         size_t error, readlen;
 119
 120         while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
 121                 error = fwrite(cp, sizeof(char), readlen, stdout);
 122                 if (error != readlen)
 123                         err(1, "stdout");
 124                 cnt--;
 125         }
 126 }
 127
 128 static void
 129 head_bytes(FILE *fp, size_t cnt)
 130 {
 131         char buf[4096];
 132         size_t readlen;
 133
 134         while (cnt) {
 135                 if (cnt < sizeof(buf))
 136                         readlen = cnt;
 137                 else
 138                         readlen = sizeof(buf);
 139                 readlen = fread(buf, sizeof(char), readlen, fp);
 140                 if (readlen == 0)
 141                         break;
 142                 if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
 143                         err(1, "stdout");
 144                 cnt -= readlen;
 145         }
 146 }
 147
 148 static void
 149 obsolete(char **argv)
 150 {
 151         char *ap;
 152
 153         while ((ap = *++argv)) {
 154                 /* Return if "--" or not "-[0-9]*". */
 155                 if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
 156                         return;
 157                 if ((ap = malloc(strlen(*argv) + 2)) == NULL)
 158                         err(1, "malloc failed");
 159                 ap[0] = '-';
 160                 ap[1] = 'n';
 161                 strcpy(ap + 2, *argv + 1);
 162                 *argv = ap;
 163         }
 164 }
 165
 166 static void
 167 usage(void)
 168 {
 169         fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
 170         exit(1);
 171 }