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  * 4. 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
  30 #ifndef lint
  31 static const char copyright[] =
  32 "@(#) Copyright (c) 1980, 1987, 1992, 1993\n\
  33         The Regents of the University of California.  All rights reserved.\n";
  34 #endif /* not lint */
  35
  36 #ifndef lint
  37 #if 0
  38 static char sccsid[] = "@(#)head.c      8.2 (Berkeley) 5/4/95";
  39 #endif
  40 #endif /* not lint */
  41 #include <sys/cdefs.h>
  42 __FBSDID("$FreeBSD$");
  43
  44 #include <sys/types.h>
  45
  46 #include <ctype.h>
  47 #include <err.h>
  48 #include <inttypes.h>
  49 #include <stdio.h>
  50 #include <stdlib.h>
  51 #include <string.h>
  52 #include <unistd.h>
  53
  54 /*
  55  * head - give the first few lines of a stream or of each of a set of files
  56  *
  57  * Bill Joy UCB August 24, 1977
  58  */
  59
  60 static void head(FILE *, int);
  61 static void head_bytes(FILE *, off_t);
  62 static void obsolete(char *[]);
  63 static void usage(void);
  64
  65 int
  66 main(int argc, char *argv[])
  67 {
  68         int ch;
  69         FILE *fp;
  70         int first, linecnt = -1, eval = 0;
  71         off_t bytecnt = -1;
  72         char *ep;
  73
  74         obsolete(argv);
  75         while ((ch = getopt(argc, argv, "n:c:")) != -1)
  76                 switch(ch) {
  77                 case 'c':
  78                         bytecnt = strtoimax(optarg, &ep, 10);
  79                         if (*ep || bytecnt <= 0)
  80                                 errx(1, "illegal byte count -- %s", optarg);
  81                         break;
  82                 case 'n':
  83                         linecnt = strtol(optarg, &ep, 10);
  84                         if (*ep || linecnt <= 0)
  85                                 errx(1, "illegal line count -- %s", optarg);
  86                         break;
  87                 case '?':
  88                 default:
  89                         usage();
  90                 }
  91         argc -= optind;
  92         argv += optind;
  93
  94         if (linecnt != -1 && bytecnt != -1)
  95                 errx(1, "can't combine line and byte counts");
  96         if (linecnt == -1 )
  97                 linecnt = 10;
  98         if (*argv) {
  99                 for (first = 1; *argv; ++argv) {
 100                         if ((fp = fopen(*argv, "r")) == NULL) {
 101                                 warn("%s", *argv);
 102                                 eval = 1;
 103                                 continue;
 104                         }
 105                         if (argc > 1) {
 106                                 (void)printf("%s==> %s <==\n",
 107                                     first ? "" : "\n", *argv);
 108                                 first = 0;
 109                         }
 110                         if (bytecnt == -1)
 111                                 head(fp, linecnt);
 112                         else
 113                                 head_bytes(fp, bytecnt);
 114                         (void)fclose(fp);
 115                 }
 116         } else if (bytecnt == -1)
 117                 head(stdin, linecnt);
 118         else
 119                 head_bytes(stdin, bytecnt);
 120
 121         exit(eval);
 122 }
 123
 124 static void
 125 head(FILE *fp, int cnt)
 126 {
 127         char *cp;
 128         size_t error, readlen;
 129
 130         while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
 131                 error = fwrite(cp, sizeof(char), readlen, stdout);
 132                 if (error != readlen)
 133                         err(1, "stdout");
 134                 cnt--;
 135         }
 136 }
 137
 138 static void
 139 head_bytes(FILE *fp, off_t cnt)
 140 {
 141         char buf[4096];
 142         size_t readlen;
 143
 144         while (cnt) {
 145                 if ((uintmax_t)cnt < sizeof(buf))
 146                         readlen = cnt;
 147                 else
 148                         readlen = sizeof(buf);
 149                 readlen = fread(buf, sizeof(char), readlen, fp);
 150                 if (readlen == 0)
 151                         break;
 152                 if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
 153                         err(1, "stdout");
 154                 cnt -= readlen;
 155         }
 156 }
 157
 158 static void
 159 obsolete(char *argv[])
 160 {
 161         char *ap;
 162
 163         while ((ap = *++argv)) {
 164                 /* Return if "--" or not "-[0-9]*". */
 165                 if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
 166                         return;
 167                 if ((ap = malloc(strlen(*argv) + 2)) == NULL)
 168                         err(1, NULL);
 169                 ap[0] = '-';
 170                 ap[1] = 'n';
 171                 (void)strcpy(ap + 2, *argv + 1);
 172                 *argv = ap;
 173         }
 174 }
 175
 176 static void
 177 usage(void)
 178 {
 179
 180         (void)fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
 181         exit(1);
 182 }