blob: 176e91e3aa0b556aa21a650d49b82cef6a1018f8
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 | //config:config HEAD |
10 | //config: bool "head" |
11 | //config: default y |
12 | //config: help |
13 | //config: head is used to print the first specified number of lines |
14 | //config: from files. |
15 | //config: |
16 | //config:config FEATURE_FANCY_HEAD |
17 | //config: bool "Enable head options (-c, -q, and -v)" |
18 | //config: default y |
19 | //config: depends on HEAD |
20 | //config: help |
21 | //config: This enables the head options (-c, -q, and -v). |
22 | |
23 | //applet:IF_HEAD(APPLET_NOEXEC(head, head, BB_DIR_USR_BIN, BB_SUID_DROP, head)) |
24 | |
25 | //kbuild:lib-$(CONFIG_HEAD) += head.o |
26 | |
27 | /* BB_AUDIT SUSv3 compliant */ |
28 | /* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */ |
29 | /* http://www.opengroup.org/onlinepubs/007904975/utilities/head.html */ |
30 | |
31 | //usage:#define head_trivial_usage |
32 | //usage: "[OPTIONS] [FILE]..." |
33 | //usage:#define head_full_usage "\n\n" |
34 | //usage: "Print first 10 lines of each FILE (or stdin) to stdout.\n" |
35 | //usage: "With more than one FILE, precede each with a filename header.\n" |
36 | //usage: "\n -n N[kbm] Print first N lines" |
37 | //usage: IF_FEATURE_FANCY_HEAD( |
38 | //usage: "\n -n -N[kbm] Print all except N last lines" |
39 | //usage: "\n -c [-]N[kbm] Print first N bytes" |
40 | //usage: "\n -q Never print headers" |
41 | //usage: "\n -v Always print headers" |
42 | //usage: ) |
43 | //usage: "\n" |
44 | //usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)." |
45 | //usage: |
46 | //usage:#define head_example_usage |
47 | //usage: "$ head -n 2 /etc/passwd\n" |
48 | //usage: "root:x:0:0:root:/root:/bin/bash\n" |
49 | //usage: "daemon:x:1:1:daemon:/usr/sbin:/bin/sh\n" |
50 | |
51 | #include "libbb.h" |
52 | |
53 | /* This is a NOEXEC applet. Be very careful! */ |
54 | |
55 | #if !ENABLE_FEATURE_FANCY_HEAD |
56 | # define print_first_N(fp,count,bytes) print_first_N(fp,count) |
57 | #endif |
58 | static void |
59 | print_first_N(FILE *fp, unsigned long count, bool count_bytes) |
60 | { |
61 | #if !ENABLE_FEATURE_FANCY_HEAD |
62 | const int count_bytes = 0; |
63 | #endif |
64 | while (count) { |
65 | int c = getc(fp); |
66 | if (c == EOF) |
67 | break; |
68 | if (count_bytes || (c == '\n')) |
69 | --count; |
70 | putchar(c); |
71 | } |
72 | } |
73 | |
74 | #if ENABLE_FEATURE_FANCY_HEAD |
75 | static void |
76 | print_except_N_last_bytes(FILE *fp, unsigned count) |
77 | { |
78 | unsigned char *circle = xmalloc(++count); |
79 | unsigned head = 0; |
80 | for(;;) { |
81 | int c; |
82 | c = getc(fp); |
83 | if (c == EOF) |
84 | goto ret; |
85 | circle[head++] = c; |
86 | if (head == count) |
87 | break; |
88 | } |
89 | for (;;) { |
90 | int c; |
91 | if (head == count) |
92 | head = 0; |
93 | putchar(circle[head]); |
94 | c = getc(fp); |
95 | if (c == EOF) |
96 | goto ret; |
97 | circle[head] = c; |
98 | head++; |
99 | } |
100 | ret: |
101 | free(circle); |
102 | } |
103 | |
104 | static void |
105 | print_except_N_last_lines(FILE *fp, unsigned count) |
106 | { |
107 | char **circle = xzalloc((++count) * sizeof(circle[0])); |
108 | unsigned head = 0; |
109 | for(;;) { |
110 | char *c; |
111 | c = xmalloc_fgets(fp); |
112 | if (!c) |
113 | goto ret; |
114 | circle[head++] = c; |
115 | if (head == count) |
116 | break; |
117 | } |
118 | for (;;) { |
119 | char *c; |
120 | if (head == count) |
121 | head = 0; |
122 | fputs(circle[head], stdout); |
123 | c = xmalloc_fgets(fp); |
124 | if (!c) |
125 | goto ret; |
126 | free(circle[head]); |
127 | circle[head++] = c; |
128 | } |
129 | ret: |
130 | head = 0; |
131 | for(;;) { |
132 | free(circle[head++]); |
133 | if (head == count) |
134 | break; |
135 | } |
136 | free(circle); |
137 | } |
138 | #else |
139 | /* Must never be called */ |
140 | void print_except_N_last_bytes(FILE *fp, unsigned count); |
141 | void print_except_N_last_lines(FILE *fp, unsigned count); |
142 | #endif |
143 | |
144 | #if !ENABLE_FEATURE_FANCY_HEAD |
145 | # define eat_num(negative_N,p) eat_num(p) |
146 | #endif |
147 | static unsigned long |
148 | eat_num(bool *negative_N, const char *p) |
149 | { |
150 | #if ENABLE_FEATURE_FANCY_HEAD |
151 | if (*p == '-') { |
152 | *negative_N = 1; |
153 | p++; |
154 | } |
155 | #endif |
156 | return xatoul_sfx(p, bkm_suffixes); |
157 | } |
158 | |
159 | static const char head_opts[] ALIGN1 = |
160 | "n:" |
161 | #if ENABLE_FEATURE_FANCY_HEAD |
162 | "c:qv" |
163 | #endif |
164 | ; |
165 | |
166 | #define header_fmt_str "\n==> %s <==\n" |
167 | |
168 | int head_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
169 | int head_main(int argc, char **argv) |
170 | { |
171 | unsigned long count = 10; |
172 | #if ENABLE_FEATURE_FANCY_HEAD |
173 | int header_threshhold = 1; |
174 | bool count_bytes = 0; |
175 | bool negative_N = 0; |
176 | #else |
177 | # define header_threshhold 1 |
178 | # define count_bytes 0 |
179 | # define negative_N 0 |
180 | #endif |
181 | FILE *fp; |
182 | const char *fmt; |
183 | char *p; |
184 | int opt; |
185 | int retval = EXIT_SUCCESS; |
186 | |
187 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD |
188 | /* Allow legacy syntax of an initial numeric option without -n. */ |
189 | if (argv[1] && argv[1][0] == '-' |
190 | && isdigit(argv[1][1]) |
191 | ) { |
192 | --argc; |
193 | ++argv; |
194 | p = argv[0] + 1; |
195 | goto GET_COUNT; |
196 | } |
197 | #endif |
198 | |
199 | /* No size benefit in converting this to getopt32 */ |
200 | while ((opt = getopt(argc, argv, head_opts)) > 0) { |
201 | switch (opt) { |
202 | #if ENABLE_FEATURE_FANCY_HEAD |
203 | case 'q': |
204 | header_threshhold = INT_MAX; |
205 | break; |
206 | case 'v': |
207 | header_threshhold = -1; |
208 | break; |
209 | case 'c': |
210 | count_bytes = 1; |
211 | /* fall through */ |
212 | #endif |
213 | case 'n': |
214 | p = optarg; |
215 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD |
216 | GET_COUNT: |
217 | #endif |
218 | count = eat_num(&negative_N, p); |
219 | break; |
220 | default: |
221 | bb_show_usage(); |
222 | } |
223 | } |
224 | |
225 | argc -= optind; |
226 | argv += optind; |
227 | if (!*argv) |
228 | *--argv = (char*)"-"; |
229 | |
230 | fmt = header_fmt_str + 1; |
231 | if (argc <= header_threshhold) { |
232 | #if ENABLE_FEATURE_FANCY_HEAD |
233 | header_threshhold = 0; |
234 | #else |
235 | fmt += 11; /* "" */ |
236 | #endif |
237 | } |
238 | if (negative_N) { |
239 | if (count >= INT_MAX / sizeof(char*)) |
240 | bb_error_msg("count is too big: %lu", count); |
241 | } |
242 | |
243 | do { |
244 | fp = fopen_or_warn_stdin(*argv); |
245 | if (fp) { |
246 | if (fp == stdin) { |
247 | *argv = (char *) bb_msg_standard_input; |
248 | } |
249 | if (header_threshhold) { |
250 | printf(fmt, *argv); |
251 | } |
252 | if (negative_N) { |
253 | if (count_bytes) { |
254 | print_except_N_last_bytes(fp, count); |
255 | } else { |
256 | print_except_N_last_lines(fp, count); |
257 | } |
258 | } else { |
259 | print_first_N(fp, count, count_bytes); |
260 | } |
261 | die_if_ferror_stdout(); |
262 | if (fclose_if_not_stdin(fp)) { |
263 | bb_simple_perror_msg(*argv); |
264 | retval = EXIT_FAILURE; |
265 | } |
266 | } else { |
267 | retval = EXIT_FAILURE; |
268 | } |
269 | fmt = header_fmt_str; |
270 | } while (*++argv); |
271 | |
272 | fflush_stdout_and_exit(retval); |
273 | } |
274 |