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 source tree.
   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 "libbb.h"
  15
  16 /* This is a NOEXEC applet. Be very careful! */
  17
  18 static const char head_opts[] ALIGN1 =
  19         "n:"
  20 #if ENABLE_FEATURE_FANCY_HEAD
  21         "c:qv"
  22 #endif
  23         ;
  24
  25 static const struct suffix_mult head_suffixes[] = {
  26         { "b", 512 },
  27         { "k", 1024 },
  28         { "m", 1024*1024 },
  29         { "", 0 }
  30 };
  31
  32 #define header_fmt_str "\n==> %s <==\n"
  33
  34 int head_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  35 int head_main(int argc, char **argv)
  36 {
  37         unsigned long count = 10;
  38         unsigned long i;
  39 #if ENABLE_FEATURE_FANCY_HEAD
  40         int count_bytes = 0;
  41         int header_threshhold = 1;
  42 #endif
  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_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
  51         /* Allow legacy syntax of an initial numeric option without -n. */
  52         if (argv[1] && argv[1][0] == '-'
  53          && isdigit(argv[1][1])
  54         ) {
  55                 --argc;
  56                 ++argv;
  57                 p = (*argv) + 1;
  58                 goto GET_COUNT;
  59         }
  60 #endif
  61
  62         /* No size benefit in converting this to getopt32 */
  63         while ((opt = getopt(argc, argv, head_opts)) > 0) {
  64                 switch (opt) {
  65 #if ENABLE_FEATURE_FANCY_HEAD
  66                 case 'q':
  67                         header_threshhold = INT_MAX;
  68                         break;
  69                 case 'v':
  70                         header_threshhold = -1;
  71                         break;
  72                 case 'c':
  73                         count_bytes = 1;
  74                         /* fall through */
  75 #endif
  76                 case 'n':
  77                         p = optarg;
  78 #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
  79  GET_COUNT:
  80 #endif
  81                         count = xatoul_sfx(p, head_suffixes);
  82                         break;
  83                 default:
  84                         bb_show_usage();
  85                 }
  86         }
  87
  88         argc -= optind;
  89         argv += optind;
  90         if (!*argv)
  91                 *--argv = (char*)"-";
  92
  93         fmt = header_fmt_str + 1;
  94 #if ENABLE_FEATURE_FANCY_HEAD
  95         if (argc <= header_threshhold) {
  96                 header_threshhold = 0;
  97         }
  98 #else
  99         if (argc <= 1) {
 100                 fmt += 11; /* "" */
 101         }
 102         /* Now define some things here to avoid #ifdefs in the code below.
 103          * These should optimize out of the if conditions below. */
 104 #define header_threshhold   1
 105 #define count_bytes         0
 106 #endif
 107
 108         do {
 109                 fp = fopen_or_warn_stdin(*argv);
 110                 if (fp) {
 111                         if (fp == stdin) {
 112                                 *argv = (char *) bb_msg_standard_input;
 113                         }
 114                         if (header_threshhold) {
 115                                 printf(fmt, *argv);
 116                         }
 117                         i = count;
 118                         while (i && ((c = getc(fp)) != EOF)) {
 119                                 if (count_bytes || (c == '\n')) {
 120                                         --i;
 121                                 }
 122                                 putchar(c);
 123                         }
 124                         if (fclose_if_not_stdin(fp)) {
 125                                 bb_simple_perror_msg(*argv);
 126                                 retval = EXIT_FAILURE;
 127                         }
 128                         die_if_ferror_stdout();
 129                 } else {
 130                         retval = EXIT_FAILURE;
 131                 }
 132                 fmt = header_fmt_str;
 133         } while (*++argv);
 134
 135         fflush_stdout_and_exit(retval);
 136 }