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