1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * head implementation for busybox
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4 | *
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5 | * Copyright (C) 2003 Manuel Novoa III <mjn3@codepoet.org>
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6 | *
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7 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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8 | */
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9 |
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10 | /* BB_AUDIT SUSv3 compliant */
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11 | /* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
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12 | /* http://www.opengroup.org/onlinepubs/007904975/utilities/head.html */
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13 |
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14 | //usage:#define head_trivial_usage
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15 | //usage: "[OPTIONS] [FILE]..."
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16 | //usage:#define head_full_usage "\n\n"
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17 | //usage: "Print first 10 lines of each FILE (or stdin) to stdout.\n"
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18 | //usage: "With more than one FILE, precede each with a filename header.\n"
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19 | //usage: "\n -n N[kbm] Print first N lines"
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20 | //usage: IF_FEATURE_FANCY_HEAD(
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21 | //usage: "\n -c N[kbm] Print first N bytes"
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22 | //usage: "\n -q Never print headers"
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23 | //usage: "\n -v Always print headers"
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24 | //usage: )
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25 | //usage: "\n"
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26 | //usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
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27 | //usage:
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28 | //usage:#define head_example_usage
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29 | //usage: "$ head -n 2 /etc/passwd\n"
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30 | //usage: "root:x:0:0:root:/root:/bin/bash\n"
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31 | //usage: "daemon:x:1:1:daemon:/usr/sbin:/bin/sh\n"
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32 |
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33 | #include "libbb.h"
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34 |
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35 | /* This is a NOEXEC applet. Be very careful! */
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36 |
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37 | static const char head_opts[] ALIGN1 =
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38 | "n:"
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39 | #if ENABLE_FEATURE_FANCY_HEAD
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40 | "c:qv"
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41 | #endif
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42 | ;
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43 |
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44 | static const struct suffix_mult head_suffixes[] = {
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45 | { "b", 512 },
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46 | { "k", 1024 },
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47 | { "m", 1024*1024 },
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48 | { "", 0 }
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49 | };
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50 |
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51 | #define header_fmt_str "\n==> %s <==\n"
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52 |
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53 | int head_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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54 | int head_main(int argc, char **argv)
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55 | {
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56 | unsigned long count = 10;
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57 | unsigned long i;
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58 | #if ENABLE_FEATURE_FANCY_HEAD
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59 | int count_bytes = 0;
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60 | int header_threshhold = 1;
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61 | #endif
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62 | FILE *fp;
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63 | const char *fmt;
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64 | char *p;
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65 | int opt;
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66 | int c;
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67 | int retval = EXIT_SUCCESS;
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68 |
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69 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
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70 | /* Allow legacy syntax of an initial numeric option without -n. */
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71 | if (argv[1] && argv[1][0] == '-'
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72 | && isdigit(argv[1][1])
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73 | ) {
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74 | --argc;
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75 | ++argv;
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76 | p = (*argv) + 1;
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77 | goto GET_COUNT;
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78 | }
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79 | #endif
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80 |
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81 | /* No size benefit in converting this to getopt32 */
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82 | while ((opt = getopt(argc, argv, head_opts)) > 0) {
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83 | switch (opt) {
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84 | #if ENABLE_FEATURE_FANCY_HEAD
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85 | case 'q':
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86 | header_threshhold = INT_MAX;
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87 | break;
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88 | case 'v':
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89 | header_threshhold = -1;
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90 | break;
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91 | case 'c':
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92 | count_bytes = 1;
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93 | /* fall through */
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94 | #endif
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95 | case 'n':
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96 | p = optarg;
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97 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
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98 | GET_COUNT:
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99 | #endif
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100 | count = xatoul_sfx(p, head_suffixes);
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101 | break;
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102 | default:
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103 | bb_show_usage();
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104 | }
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105 | }
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106 |
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107 | argc -= optind;
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108 | argv += optind;
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109 | if (!*argv)
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110 | *--argv = (char*)"-";
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111 |
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112 | fmt = header_fmt_str + 1;
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113 | #if ENABLE_FEATURE_FANCY_HEAD
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114 | if (argc <= header_threshhold) {
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115 | header_threshhold = 0;
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116 | }
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117 | #else
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118 | if (argc <= 1) {
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119 | fmt += 11; /* "" */
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120 | }
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121 | /* Now define some things here to avoid #ifdefs in the code below.
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122 | * These should optimize out of the if conditions below. */
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123 | #define header_threshhold 1
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124 | #define count_bytes 0
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125 | #endif
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126 |
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127 | do {
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128 | fp = fopen_or_warn_stdin(*argv);
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129 | if (fp) {
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130 | if (fp == stdin) {
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131 | *argv = (char *) bb_msg_standard_input;
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132 | }
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133 | if (header_threshhold) {
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134 | printf(fmt, *argv);
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135 | }
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136 | i = count;
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137 | while (i && ((c = getc(fp)) != EOF)) {
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138 | if (count_bytes || (c == '\n')) {
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139 | --i;
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140 | }
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141 | putchar(c);
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142 | }
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143 | if (fclose_if_not_stdin(fp)) {
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144 | bb_simple_perror_msg(*argv);
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145 | retval = EXIT_FAILURE;
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146 | }
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147 | die_if_ferror_stdout();
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148 | } else {
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149 | retval = EXIT_FAILURE;
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150 | }
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151 | fmt = header_fmt_str;
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152 | } while (*++argv);
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153 |
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154 | fflush_stdout_and_exit(retval);
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155 | }
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