text_cmds/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
  34 #ifndef lint
  35 static const char copyright[] =
  36 "@(#) Copyright (c) 1980, 1987, 1992, 1993\n\
  37         The Regents of the University of California.  All rights reserved.\n";
  38 #endif /* not lint */
  39
  40 #ifndef lint
  41 #if 0
  42 static char sccsid[] = "@(#)head.c      8.2 (Berkeley) 5/4/95";
  43 #endif
  44 #endif /* not lint */
  45 #include <sys/cdefs.h>
  46 __FBSDID("$FreeBSD: src/usr.bin/head/head.c,v 1.20 2007/01/11 20:23:01 brooks Exp $");
  47
  48 #include <sys/types.h>
  49
  50 #include <ctype.h>
  51 #include <err.h>
  52 #include <inttypes.h>
  53 #include <stdio.h>
  54 #include <stdlib.h>
  55 #include <string.h>
  56 #include <unistd.h>
  57
  58 /*
  59  * head - give the first few lines of a stream or of each of a set of files
  60  *
  61  * Bill Joy UCB August 24, 1977
  62  */
  63
  64 static void head(FILE *, int);
  65 static void head_bytes(FILE *, off_t);
  66 static void obsolete(char *[]);
  67 static void usage(void);
  68
  69 int
  70 main(int argc, char *argv[])
  71 {
  72         int ch;
  73         FILE *fp;
  74         int first, linecnt = -1, eval = 0;
  75         off_t bytecnt = -1;
  76         char *ep;
  77
  78         obsolete(argv);
  79         while ((ch = getopt(argc, argv, "n:c:")) != -1)
  80                 switch(ch) {
  81                 case 'c':
  82                         bytecnt = strtoimax(optarg, &ep, 10);
  83                         if (*ep || bytecnt <= 0)
  84                                 errx(1, "illegal byte count -- %s", optarg);
  85                         break;
  86                 case 'n':
  87                         linecnt = strtol(optarg, &ep, 10);
  88                         if (*ep || linecnt <= 0)
  89                                 errx(1, "illegal line count -- %s", optarg);
  90                         break;
  91                 case '?':
  92                 default:
  93                         usage();
  94                 }
  95         argc -= optind;
  96         argv += optind;
  97
  98         if (linecnt != -1 && bytecnt != -1)
  99                 errx(1, "can't combine line and byte counts");
 100         if (linecnt == -1 )
 101                 linecnt = 10;
 102         if (*argv) {
 103                 for (first = 1; *argv; ++argv) {
 104                         if ((fp = fopen(*argv, "r")) == NULL) {
 105                                 warn("%s", *argv);
 106                                 eval = 1;
 107                                 continue;
 108                         }
 109                         if (argc > 1) {
 110                                 (void)printf("%s==> %s <==\n",
 111                                     first ? "" : "\n", *argv);
 112                                 first = 0;
 113                         }
 114                         if (bytecnt == -1)
 115                                 head(fp, linecnt);
 116                         else
 117                                 head_bytes(fp, bytecnt);
 118                         if (ferror(fp)) {
 119                                 warnx("Error reading %s", *argv);
 120                                 eval = 1;
 121                         }
 122                         (void)fclose(fp);
 123                 }
 124         } else {
 125                 if (bytecnt == -1) {
 126                         head(stdin, linecnt);
 127                 } else {
 128                         head_bytes(stdin, bytecnt);
 129                 }
 130                 if (ferror(stdin)) {
 131                         warnx("Error reading stdin");
 132                         eval = 1;
 133                 }
 134         }
 135
 136         exit(eval);
 137 }
 138
 139 static void
 140 head(FILE *fp, int cnt)
 141 {
 142         char *cp;
 143         size_t error, readlen;
 144
 145         while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
 146                 error = fwrite(cp, sizeof(char), readlen, stdout);
 147                 if (error != readlen)
 148                         err(1, "stdout");
 149                 cnt--;
 150         }
 151
 152         fflush(fp);
 153 }
 154
 155 static void
 156 head_bytes(FILE *fp, off_t cnt)
 157 {
 158         char buf[4096];
 159         size_t readlen;
 160
 161         while (cnt) {
 162                 if ((uintmax_t)cnt < sizeof(buf))
 163                         readlen = cnt;
 164                 else
 165                         readlen = sizeof(buf);
 166                 readlen = fread(buf, sizeof(char), readlen, fp);
 167                 if (readlen == 0)
 168                         break;
 169                 if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
 170                         err(1, "stdout");
 171                 cnt -= readlen;
 172         }
 173 }
 174
 175 static void
 176 obsolete(char *argv[])
 177 {
 178         char *ap;
 179
 180         while ((ap = *++argv)) {
 181                 /* Return if "--" or not "-[0-9]*". */
 182                 if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
 183                         return;
 184                 if ((ap = malloc(strlen(*argv) + 2)) == NULL)
 185                         err(1, NULL);
 186                 ap[0] = '-';
 187                 ap[1] = 'n';
 188                 (void)strcpy(ap + 2, *argv + 1);
 189                 *argv = ap;
 190         }
 191 }
 192
 193 static void
 194 usage(void)
 195 {
 196
 197         (void)fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
 198         exit(1);
 199 }