coreutils/head.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * head implementation for busybox
   4  *
   5  * Copyright (C) 2003  Manuel Novoa III  <mjn3@codepoet.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15  * General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  20  *
  21  */
  22
  23 /* BB_AUDIT SUSv3 compliant */
  24 /* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
  25 /* http://www.opengroup.org/onlinepubs/007904975/utilities/head.html */
  26
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <limits.h>
  30 #include <ctype.h>
  31 #include <unistd.h>
  32 #include "busybox.h"
  33
  34 static const char head_opts[] =
  35         "n:"
  36 #if ENABLE_FEATURE_FANCY_HEAD
  37         "c:qv"
  38 #endif
  39         ;
  40
  41 static const char header_fmt_str[] = "\n==> %s <==\n";
  42
  43 int head_main(int argc, char **argv)
  44 {
  45         unsigned long count = 10;
  46         unsigned long i;
  47 #if ENABLE_FEATURE_FANCY_HEAD
  48         int count_bytes = 0;
  49         int header_threshhold = 1;
  50 #endif
  51
  52         FILE *fp;
  53         const char *fmt;
  54         char *p;
  55         int opt;
  56         int c;
  57         int retval = EXIT_SUCCESS;
  58
  59 #if defined CONFIG_FEATURE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
  60         /* Allow legacy syntax of an initial numeric option without -n. */
  61         if ((argc > 1) && (argv[1][0] == '-')
  62                 /* && (isdigit)(argv[1][1]) */
  63                 && (((unsigned int)(argv[1][1] - '0')) <= 9)
  64         ) {
  65                 --argc;
  66                 ++argv;
  67                 p = (*argv) + 1;
  68                 goto GET_COUNT;
  69         }
  70 #endif
  71
  72         /* No size benefit in converting this to bb_getopt_ulflags */
  73         while ((opt = getopt(argc, argv, head_opts)) > 0) {
  74                 switch(opt) {
  75 #if ENABLE_FEATURE_FANCY_HEAD
  76                         case 'q':
  77                                 header_threshhold = INT_MAX;
  78                                 break;
  79                         case 'v':
  80                                 header_threshhold = -1;
  81                                 break;
  82                         case 'c':
  83                                 count_bytes = 1;
  84                                 /* fall through */
  85 #endif
  86                         case 'n':
  87                                 p = optarg;
  88 #if defined CONFIG_FEATURE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
  89                         GET_COUNT:
  90 #endif
  91                                 count = bb_xgetularg10(p);
  92                                 break;
  93                         default:
  94                                 bb_show_usage();
  95                 }
  96         }
  97
  98         argv += optind;
  99         if (!*argv) {
 100                 *--argv = "-";
 101         }
 102
 103         fmt = header_fmt_str + 1;
 104 #if ENABLE_FEATURE_FANCY_HEAD
 105         if (argc - optind <= header_threshhold) {
 106                 header_threshhold = 0;
 107         }
 108 #else
 109         if (argc <= optind + 1) {
 110                 fmt += 11;
 111         }
 112         /* Now define some things here to avoid #ifdefs in the code below.
 113          * These should optimize out of the if conditions below. */
 114 #define header_threshhold   1
 115 #define count_bytes         0
 116 #endif
 117
 118         do {
 119                 if ((fp = bb_wfopen_input(*argv)) != NULL) {
 120                         if (fp == stdin) {
 121                                 *argv = (char *) bb_msg_standard_input;
 122                         }
 123                         if (header_threshhold) {
 124                                 bb_printf(fmt, *argv);
 125                         }
 126                         i = count;
 127                         while (i && ((c = getc(fp)) != EOF)) {
 128                                 if (count_bytes || (c == '\n')) {
 129                                         --i;
 130                                 }
 131                                 putchar(c);
 132                         }
 133                         if (bb_fclose_nonstdin(fp)) {
 134                                 bb_perror_msg("%s", *argv);     /* Avoid multibyte problems. */
 135                                 retval = EXIT_FAILURE;
 136                         }
 137                         bb_xferror_stdout();
 138                 }
 139                 fmt = header_fmt_str;
 140         } while (*++argv);
 141
 142         bb_fflush_stdout_and_exit(retval);
 143 }