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  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
   8  */
   9
  10 /* BB_AUDIT SUSv3 compliant */
  11 /* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
  12 /* http://www.opengroup.org/onlinepubs/007904975/utilities/head.html */
  13
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <limits.h>
  17 #include <ctype.h>
  18 #include <unistd.h>
  19 #include "busybox.h"
  20
  21 static const char head_opts[] =
  22         "n:"
  23 #if ENABLE_FEATURE_FANCY_HEAD
  24         "c:qv"
  25 #endif
  26         ;
  27
  28 #if ENABLE_FEATURE_FANCY_HEAD
  29 static const struct suffix_mult head_suffixes[] = {
  30         { "b", 512 },
  31         { "k", 1024 },
  32         { "m", 1024*1024 },
  33         { NULL, 0 }
  34 };
  35 #endif
  36
  37 static const char header_fmt_str[] = "\n==> %s <==\n";
  38
  39 int head_main(int argc, char **argv)
  40 {
  41         unsigned long count = 10;
  42         unsigned long i;
  43 #if ENABLE_FEATURE_FANCY_HEAD
  44         int count_bytes = 0;
  45         int header_threshhold = 1;
  46 #endif
  47
  48         FILE *fp;
  49         const char *fmt;
  50         char *p;
  51         int opt;
  52         int c;
  53         int retval = EXIT_SUCCESS;
  54
  55 #if !ENABLE_DEBUG_YANK_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
  56         /* Allow legacy syntax of an initial numeric option without -n. */
  57         if ((argc > 1) && (argv[1][0] == '-')
  58                 /* && (isdigit)(argv[1][1]) */
  59                 && (((unsigned int)(argv[1][1] - '0')) <= 9)
  60         ) {
  61                 --argc;
  62                 ++argv;
  63                 p = (*argv) + 1;
  64                 goto GET_COUNT;
  65         }
  66 #endif
  67
  68         /* No size benefit in converting this to bb_getopt_ulflags */
  69         while ((opt = getopt(argc, argv, head_opts)) > 0) {
  70                 switch(opt) {
  71 #if ENABLE_FEATURE_FANCY_HEAD
  72                         case 'q':
  73                                 header_threshhold = INT_MAX;
  74                                 break;
  75                         case 'v':
  76                                 header_threshhold = -1;
  77                                 break;
  78                         case 'c':
  79                                 count_bytes = 1;
  80                                 /* fall through */
  81 #endif
  82                         case 'n':
  83                                 p = optarg;
  84 #if !ENABLE_DEBUG_YANK_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
  85                         GET_COUNT:
  86 #endif
  87
  88 #if !ENABLE_FEATURE_FANCY_HEAD
  89                                 count = bb_xgetularg10(p);
  90 #else
  91                                 count = bb_xgetularg_bnd_sfx(p, 10,
  92                                                                 0, ULONG_MAX,
  93                                                                 head_suffixes);
  94 #endif
  95                                 break;
  96                         default:
  97                                 bb_show_usage();
  98                 }
  99         }
 100
 101         argv += optind;
 102         if (!*argv) {
 103                 *--argv = "-";
 104         }
 105
 106         fmt = header_fmt_str + 1;
 107 #if ENABLE_FEATURE_FANCY_HEAD
 108         if (argc - optind <= header_threshhold) {
 109                 header_threshhold = 0;
 110         }
 111 #else
 112         if (argc <= optind + 1) {
 113                 fmt += 11;
 114         }
 115         /* Now define some things here to avoid #ifdefs in the code below.
 116          * These should optimize out of the if conditions below. */
 117 #define header_threshhold   1
 118 #define count_bytes         0
 119 #endif
 120
 121         do {
 122                 if ((fp = bb_wfopen_input(*argv)) != NULL) {
 123                         if (fp == stdin) {
 124                                 *argv = (char *) bb_msg_standard_input;
 125                         }
 126                         if (header_threshhold) {
 127                                 bb_printf(fmt, *argv);
 128                         }
 129                         i = count;
 130                         while (i && ((c = getc(fp)) != EOF)) {
 131                                 if (count_bytes || (c == '\n')) {
 132                                         --i;
 133                                 }
 134                                 putchar(c);
 135                         }
 136                         if (bb_fclose_nonstdin(fp)) {
 137                                 bb_perror_msg("%s", *argv);     /* Avoid multibyte problems. */
 138                                 retval = EXIT_FAILURE;
 139                         }
 140                         bb_xferror_stdout();
 141                 }
 142                 fmt = header_fmt_str;
 143         } while (*++argv);
 144
 145         bb_fflush_stdout_and_exit(retval);
 146 }