usr.bin/head/head.c

   1 /*      $NetBSD: head.c,v 1.23 2010/03/31 21:55:23 joerg Exp $  */
   2
   3 /*
   4  * Copyright (c) 1980, 1987, 1992, 1993
   5  *      The Regents of the University of California.  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 <sys/cdefs.h>
  33 #ifndef lint
  34 __COPYRIGHT("@(#) Copyright (c) 1980, 1987, 1992, 1993\
  35  The Regents of the University of California.  All rights reserved.");
  36 #endif /* not lint */
  37
  38 #ifndef lint
  39 #if 0
  40 static char sccsid[] = "@(#)head.c      8.2 (Berkeley) 5/4/95";
  41 #else
  42 __RCSID("$NetBSD: head.c,v 1.23 2010/03/31 21:55:23 joerg Exp $");
  43 #endif
  44 #endif /* not lint */
  45
  46 #include <sys/types.h>
  47
  48 #include <ctype.h>
  49 #include <err.h>
  50 #include <errno.h>
  51 #include <inttypes.h>
  52 #include <limits.h>
  53 #include <locale.h>
  54 #include <stdio.h>
  55 #include <stdlib.h>
  56 #include <string.h>
  57 #include <unistd.h>
  58
  59 /*
  60  * head - give the first few lines of a stream or of each of a set of files
  61  *
  62  * Bill Joy UCB August 24, 1977
  63  */
  64
  65 static void head(FILE *, intmax_t, intmax_t);
  66 static void obsolete(char *[]);
  67 __dead static void usage(void);
  68
  69
  70 int
  71 main(int argc, char *argv[])
  72 {
  73         int ch;
  74         FILE *fp;
  75         int first;
  76         uintmax_t linecnt;
  77         uintmax_t bytecnt;
  78         char *ep;
  79         int eval = 0;
  80         int qflag = 0;
  81         int vflag = 0;
  82
  83         (void)setlocale(LC_ALL, "");
  84         obsolete(argv);
  85         linecnt = 10;
  86         bytecnt = 0;
  87         while ((ch = getopt(argc, argv, "c:n:qv")) != -1)
  88                 switch(ch) {
  89                 case 'c':
  90                         errno = 0;
  91                         bytecnt = strtoimax(optarg, &ep, 10);
  92                         if ((bytecnt == INTMAX_MAX && errno == ERANGE) ||
  93                             *ep || bytecnt <= 0)
  94                                 errx(1, "illegal byte count -- %s", optarg);
  95                         break;
  96
  97                 case 'n':
  98                         errno = 0;
  99                         linecnt = strtoimax(optarg, &ep, 10);
 100                         if ((linecnt == INTMAX_MAX && errno == ERANGE) ||
 101                             *ep || linecnt <= 0)
 102                                 errx(1, "illegal line count -- %s", optarg);
 103                         break;
 104
 105                 case 'q':
 106                         qflag = 1;
 107                         vflag = 0;
 108                         break;
 109
 110                 case 'v':
 111                         qflag = 0;
 112                         vflag = 1;
 113                         break;
 114
 115                 case '?':
 116                 default:
 117                         usage();
 118                 }
 119         argc -= optind;
 120         argv += optind;
 121
 122         if (*argv)
 123                 for (first = 1; *argv; ++argv) {
 124                         if ((fp = fopen(*argv, "r")) == NULL) {
 125                                 warn("%s", *argv);
 126                                 eval = 1;
 127                                 continue;
 128                         }
 129                         if (vflag || (qflag == 0 && argc > 1)) {
 130                                 (void)printf("%s==> %s <==\n",
 131                                     first ? "" : "\n", *argv);
 132                                 first = 0;
 133                         }
 134                         head(fp, linecnt, bytecnt);
 135                         (void)fclose(fp);
 136                 }
 137         else
 138                 head(stdin, linecnt, bytecnt);
 139         exit(eval);
 140 }
 141
 142 static void
 143 head(FILE *fp, intmax_t cnt, intmax_t bytecnt)
 144 {
 145         char buf[65536];
 146         size_t len, rv, rv2;
 147         int ch;
 148
 149         if (bytecnt) {
 150                 while (bytecnt) {
 151                         len = sizeof(buf);
 152                         if (bytecnt > (intmax_t)sizeof(buf))
 153                                 len = sizeof(buf);
 154                         else
 155                                 len = bytecnt;
 156                         rv = fread(buf, 1, len, fp);
 157                         if (rv == 0)
 158                                 break; /* Distinguish EOF and error? */
 159                         rv2 = fwrite(buf, 1, rv, stdout);
 160                         if (rv2 != rv) {
 161                                 if (feof(stdout))
 162                                         errx(1, "EOF on stdout");
 163                                 else
 164                                         err(1, "failure writing to stdout");
 165                         }
 166                         bytecnt -= rv;
 167                 }
 168         } else {
 169                 while ((ch = getc(fp)) != EOF) {
 170                         if (putchar(ch) == EOF)
 171                                 err(1, "stdout");
 172                         if (ch == '\n' && --cnt == 0)
 173                                 break;
 174                 }
 175         }
 176 }
 177
 178 static void
 179 obsolete(char *argv[])
 180 {
 181         char *ap;
 182
 183         while ((ap = *++argv)) {
 184                 /* Return if "--" or not "-[0-9]*". */
 185                 if (ap[0] != '-' || ap[1] == '-' ||
 186                     !isdigit((unsigned char)ap[1]))
 187                         return;
 188                 if ((ap = malloc(strlen(*argv) + 2)) == NULL)
 189                         err(1, NULL);
 190                 ap[0] = '-';
 191                 ap[1] = 'n';
 192                 (void)strcpy(ap + 2, *argv + 1);
 193                 *argv = ap;
 194         }
 195 }
 196
 197 static void
 198 usage(void)
 199 {
 200
 201         (void)fprintf(stderr, "usage: %s [-n lines] [file ...]\n",
 202             getprogname());
 203         exit(1);
 204 }