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  * @(#)head.c   8.2 (Berkeley) 5/4/95
  30  * $FreeBSD: src/usr.bin/head/head.c,v 1.10.2.1 2002/02/16 12:29:04 dwmalone Exp $
  31  */
  32
  33 #include <ctype.h>
  34 #include <err.h>
  35 #include <stdbool.h>
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <string.h>
  39 #include <unistd.h>
  40
  41 /*
  42  * head - give the first few lines of a stream or of each of a set of files
  43  *
  44  * Bill Joy UCB August 24, 1977
  45  */
  46
  47 static void     head(FILE *, size_t);
  48 static void     head_bytes(FILE *, size_t);
  49 static void     obsolete(char *[]);
  50 static void     usage(void) __dead2;
  51
  52 int
  53 main(int argc, char **argv)
  54 {
  55         int ch;
  56         FILE *fp;
  57         bool first;
  58         bool qflag = false, vflag = false;
  59         int linecnt = -1, bytecnt = -1, eval = 0;
  60         char *ep;
  61
  62         obsolete(argv);
  63         while ((ch = getopt(argc, argv, "c:n:qv")) != -1) {
  64                 switch(ch) {
  65                 case 'c':
  66                         bytecnt = strtol(optarg, &ep, 10);
  67                         if (*ep != 0 || bytecnt <= 0)
  68                                 errx(1, "illegal byte count -- %s", optarg);
  69                         break;
  70                 case 'n':
  71                         linecnt = strtol(optarg, &ep, 10);
  72                         if (*ep != 0 || linecnt <= 0)
  73                                 errx(1, "illegal line count -- %s", optarg);
  74                         break;
  75                 case 'q':
  76                         qflag = true;
  77                         vflag = false;
  78                         break;
  79                 case 'v':
  80                         vflag = true;
  81                         qflag = false;
  82                         break;
  83                 default:
  84                         usage();
  85                 }
  86         }
  87         argc -= optind;
  88         argv += optind;
  89
  90         if (linecnt != -1 && bytecnt != -1)
  91                 errx(1, "can't combine line and byte counts");
  92         if (linecnt == -1 )
  93                 linecnt = 10;
  94         if (*argv) {
  95                 first = true;
  96                 for (; *argv; ++argv) {
  97                         if ((fp = fopen(*argv, "r")) == NULL) {
  98                                 warn("%s", *argv);
  99                                 eval = 1;
 100                                 continue;
 101                         }
 102                         if (vflag || (!qflag && argc > 1)) {
 103                                 printf("%s==> %s <==\n",
 104                                     first ? "" : "\n", *argv);
 105                                 first = false;
 106                         }
 107                         if (bytecnt == -1)
 108                                 head(fp, linecnt);
 109                         else
 110                                 head_bytes(fp, bytecnt);
 111                         fclose(fp);
 112                 }
 113         } else if (bytecnt == -1)
 114                 head(stdin, linecnt);
 115         else
 116                 head_bytes(stdin, bytecnt);
 117
 118         exit(eval);
 119 }
 120
 121 static void
 122 head(FILE *fp, size_t cnt)
 123 {
 124         char *cp;
 125         size_t error, readlen;
 126
 127         while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
 128                 error = fwrite(cp, sizeof(char), readlen, stdout);
 129                 if (error != readlen)
 130                         err(1, "stdout");
 131                 cnt--;
 132         }
 133 }
 134
 135 static void
 136 head_bytes(FILE *fp, size_t cnt)
 137 {
 138         char buf[4096];
 139         size_t readlen;
 140
 141         while (cnt) {
 142                 if (cnt < sizeof(buf))
 143                         readlen = cnt;
 144                 else
 145                         readlen = sizeof(buf);
 146                 readlen = fread(buf, sizeof(char), readlen, fp);
 147                 if (readlen == 0)
 148                         break;
 149                 if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
 150                         err(1, "stdout");
 151                 cnt -= readlen;
 152         }
 153 }
 154
 155 static void
 156 obsolete(char **argv)
 157 {
 158         char *ap;
 159
 160         while ((ap = *++argv)) {
 161                 /* Return if "--" or not "-[0-9]*". */
 162                 if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
 163                         return;
 164                 if ((ap = malloc(strlen(*argv) + 2)) == NULL)
 165                         err(1, "malloc failed");
 166                 ap[0] = '-';
 167                 ap[1] = 'n';
 168                 strcpy(ap + 2, *argv + 1);
 169                 *argv = ap;
 170         }
 171 }
 172
 173 static void __dead2
 174 usage(void)
 175 {
 176         fprintf(stderr,
 177                 "usage: head [-q | -v] [-n lines | -c bytes] [file ...]\n");
 178         exit(1);
 179 }