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 "libbb.h"
  15
  16 static const char head_opts[] ALIGN1 =
  17         "n:"
  18 #if ENABLE_FEATURE_FANCY_HEAD
  19         "c:qv"
  20 #endif
  21         ;
  22
  23 static const struct suffix_mult head_suffixes[] = {
  24         { "b", 512 },
  25         { "k", 1024 },
  26         { "m", 1024*1024 },
  27         { "", 0 }
  28 };
  29
  30 static const char header_fmt_str[] ALIGN1 = "\n==> %s <==\n";
  31
  32 int head_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  33 int head_main(int argc, char **argv)
  34 {
  35         unsigned long count = 10;
  36         unsigned long i;
  37 #if ENABLE_FEATURE_FANCY_HEAD
  38         int count_bytes = 0;
  39         int header_threshhold = 1;
  40 #endif
  41         FILE *fp;
  42         const char *fmt;
  43         char *p;
  44         int opt;
  45         int c;
  46         int retval = EXIT_SUCCESS;
  47
  48 #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
  49         /* Allow legacy syntax of an initial numeric option without -n. */
  50         if (argv[1] && argv[1][0] == '-'
  51          && isdigit(argv[1][1])
  52         ) {
  53                 --argc;
  54                 ++argv;
  55                 p = (*argv) + 1;
  56                 goto GET_COUNT;
  57         }
  58 #endif
  59
  60         /* No size benefit in converting this to getopt32 */
  61         while ((opt = getopt(argc, argv, head_opts)) > 0) {
  62                 switch (opt) {
  63 #if ENABLE_FEATURE_FANCY_HEAD
  64                 case 'q':
  65                         header_threshhold = INT_MAX;
  66                         break;
  67                 case 'v':
  68                         header_threshhold = -1;
  69                         break;
  70                 case 'c':
  71                         count_bytes = 1;
  72                         /* fall through */
  73 #endif
  74                 case 'n':
  75                         p = optarg;
  76 #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
  77  GET_COUNT:
  78 #endif
  79                         count = xatoul_sfx(p, head_suffixes);
  80                         break;
  81                 default:
  82                         bb_show_usage();
  83                 }
  84         }
  85
  86         argc -= optind;
  87         argv += optind;
  88         if (!*argv)
  89                 *--argv = (char*)"-";
  90
  91         fmt = header_fmt_str + 1;
  92 #if ENABLE_FEATURE_FANCY_HEAD
  93         if (argc <= header_threshhold) {
  94                 header_threshhold = 0;
  95         }
  96 #else
  97         if (argc <= 1) {
  98                 fmt += 11; /* "" */
  99         }
 100         /* Now define some things here to avoid #ifdefs in the code below.
 101          * These should optimize out of the if conditions below. */
 102 #define header_threshhold   1
 103 #define count_bytes         0
 104 #endif
 105
 106         do {
 107                 fp = fopen_or_warn_stdin(*argv);
 108                 if (fp) {
 109                         if (fp == stdin) {
 110                                 *argv = (char *) bb_msg_standard_input;
 111                         }
 112                         if (header_threshhold) {
 113                                 printf(fmt, *argv);
 114                         }
 115                         i = count;
 116                         while (i && ((c = getc(fp)) != EOF)) {
 117                                 if (count_bytes || (c == '\n')) {
 118                                         --i;
 119                                 }
 120                                 putchar(c);
 121                         }
 122                         if (fclose_if_not_stdin(fp)) {
 123                                 bb_simple_perror_msg(*argv);
 124                                 retval = EXIT_FAILURE;
 125                         }
 126                         die_if_ferror_stdout();
 127                 } else {
 128                         retval = EXIT_FAILURE;
 129                 }
 130                 fmt = header_fmt_str;
 131         } while (*++argv);
 132
 133         fflush_stdout_and_exit(retval);
 134 }