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 (3.8 kb)"
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 -c, -q, and -v"
18 //config: default y
19 //config: depends on HEAD
20
21 //applet:IF_HEAD(APPLET_NOEXEC(head, head, BB_DIR_USR_BIN, BB_SUID_DROP, head))
22
23 //kbuild:lib-$(CONFIG_HEAD) += head.o
24
25 /* BB_AUDIT SUSv3 compliant */
26 /* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
27 /* http://www.opengroup.org/onlinepubs/007904975/utilities/head.html */
28
29 //usage:#define head_trivial_usage
30 //usage: "[OPTIONS] [FILE]..."
31 //usage:#define head_full_usage "\n\n"
32 //usage: "Print first 10 lines of FILEs (or stdin).\n"
33 //usage: "With more than one FILE, precede each with a filename header.\n"
34 //usage: "\n -n N[bkm] Print first N lines"
35 //usage: IF_FEATURE_FANCY_HEAD(
36 //usage: "\n -n -N[bkm] Print all except N last lines"
37 //usage: "\n -c [-]N[bkm] Print first N bytes"
38 //usage: )
39 //usage: "\n (b:*512 k:*1024 m:*1024^2)"
40 //usage: IF_FEATURE_FANCY_HEAD(
41 //usage: "\n -q Never print headers"
42 //usage: "\n -v Always print headers"
43 //usage: )
44 //usage:
45 //usage:#define head_example_usage
46 //usage: "$ head -n 2 /etc/passwd\n"
47 //usage: "root:x:0:0:root:/root:/bin/bash\n"
48 //usage: "daemon:x:1:1:daemon:/usr/sbin:/bin/sh\n"
49
50 #include "libbb.h"
51
52 /* This is a NOEXEC applet. Be very careful! */
53
54 #if !ENABLE_FEATURE_FANCY_HEAD
55 # define print_first_N(fp,count,bytes) print_first_N(fp,count)
56 #endif
57 static void
print_first_N(FILE * fp,unsigned long count,bool count_bytes)58 print_first_N(FILE *fp, unsigned long count, bool count_bytes)
59 {
60 #if !ENABLE_FEATURE_FANCY_HEAD
61 const int count_bytes = 0;
62 #endif
63 while (count) {
64 int c = getc(fp);
65 if (c == EOF)
66 break;
67 if (count_bytes || (c == '\n'))
68 --count;
69 putchar(c);
70 }
71 }
72
73 #if ENABLE_FEATURE_FANCY_HEAD
74 static void
print_except_N_last_bytes(FILE * fp,unsigned count)75 print_except_N_last_bytes(FILE *fp, unsigned count)
76 {
77 unsigned char *circle = xmalloc(++count);
78 unsigned head = 0;
79 for(;;) {
80 int c;
81 c = getc(fp);
82 if (c == EOF)
83 goto ret;
84 circle[head++] = c;
85 if (head == count)
86 break;
87 }
88 for (;;) {
89 int c;
90 if (head == count)
91 head = 0;
92 putchar(circle[head]);
93 c = getc(fp);
94 if (c == EOF)
95 goto ret;
96 circle[head] = c;
97 head++;
98 }
99 ret:
100 free(circle);
101 }
102
103 static void
print_except_N_last_lines(FILE * fp,unsigned count)104 print_except_N_last_lines(FILE *fp, unsigned count)
105 {
106 char **circle = xzalloc((++count) * sizeof(circle[0]));
107 unsigned head = 0;
108 for(;;) {
109 char *c;
110 c = xmalloc_fgets(fp);
111 if (!c)
112 goto ret;
113 circle[head++] = c;
114 if (head == count)
115 break;
116 }
117 for (;;) {
118 char *c;
119 if (head == count)
120 head = 0;
121 fputs_stdout(circle[head]);
122 c = xmalloc_fgets(fp);
123 if (!c)
124 goto ret;
125 free(circle[head]);
126 circle[head++] = c;
127 }
128 ret:
129 head = 0;
130 for(;;) {
131 free(circle[head++]);
132 if (head == count)
133 break;
134 }
135 free(circle);
136 }
137 #else
138 /* Must never be called */
139 void print_except_N_last_bytes(FILE *fp, unsigned count);
140 void print_except_N_last_lines(FILE *fp, unsigned count);
141 #endif
142
143 #if !ENABLE_FEATURE_FANCY_HEAD
144 # define eat_num(negative_N,p) eat_num(p)
145 #endif
146 static unsigned long
eat_num(bool * negative_N,const char * p)147 eat_num(bool *negative_N, const char *p)
148 {
149 #if ENABLE_FEATURE_FANCY_HEAD
150 if (*p == '-') {
151 *negative_N = 1;
152 p++;
153 }
154 #endif
155 return xatoul_sfx(p, bkm_suffixes);
156 }
157
158 static const char head_opts[] ALIGN1 =
159 "n:"
160 #if ENABLE_FEATURE_FANCY_HEAD
161 "c:qv"
162 #endif
163 ;
164
165 #define header_fmt_str "\n==> %s <==\n"
166
167 int head_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
head_main(int argc,char ** argv)168 int head_main(int argc, char **argv)
169 {
170 unsigned long count = 10;
171 #if ENABLE_FEATURE_FANCY_HEAD
172 int header_threshhold = 1;
173 bool count_bytes = 0;
174 bool negative_N = 0;
175 #else
176 # define header_threshhold 1
177 # define count_bytes 0
178 # define negative_N 0
179 #endif
180 FILE *fp;
181 const char *fmt;
182 char *p;
183 int opt;
184 int retval = EXIT_SUCCESS;
185
186 #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
187 /* Allow legacy syntax of an initial numeric option without -n. */
188 if (argv[1] && argv[1][0] == '-'
189 && isdigit(argv[1][1])
190 ) {
191 --argc;
192 ++argv;
193 p = argv[0] + 1;
194 goto GET_COUNT;
195 }
196 #endif
197
198 /* No size benefit in converting this to getopt32 */
199 while ((opt = getopt(argc, argv, head_opts)) > 0) {
200 switch (opt) {
201 #if ENABLE_FEATURE_FANCY_HEAD
202 case 'q':
203 header_threshhold = INT_MAX;
204 break;
205 case 'v':
206 header_threshhold = -1;
207 break;
208 case 'c':
209 count_bytes = 1;
210 /* fall through */
211 #endif
212 case 'n':
213 p = optarg;
214 #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
215 GET_COUNT:
216 #endif
217 count = eat_num(&negative_N, p);
218 break;
219 default:
220 bb_show_usage();
221 }
222 }
223
224 argc -= optind;
225 argv += optind;
226 if (!*argv)
227 *--argv = (char*)"-";
228
229 fmt = header_fmt_str + 1;
230 if (argc <= header_threshhold) {
231 #if ENABLE_FEATURE_FANCY_HEAD
232 header_threshhold = 0;
233 #else
234 fmt += 11; /* "" */
235 #endif
236 }
237 if (negative_N) {
238 if (count >= INT_MAX / sizeof(char*))
239 bb_error_msg("count is too big: %lu", count);
240 }
241
242 do {
243 fp = fopen_or_warn_stdin(*argv);
244 if (fp) {
245 if (fp == stdin) {
246 *argv = (char *) bb_msg_standard_input;
247 }
248 if (header_threshhold) {
249 printf(fmt, *argv);
250 }
251 if (negative_N) {
252 if (count_bytes) {
253 print_except_N_last_bytes(fp, count);
254 } else {
255 print_except_N_last_lines(fp, count);
256 }
257 } else {
258 print_first_N(fp, count, count_bytes);
259 }
260 die_if_ferror_stdout();
261 if (fclose_if_not_stdin(fp)) {
262 bb_simple_perror_msg(*argv);
263 retval = EXIT_FAILURE;
264 }
265 } else {
266 retval = EXIT_FAILURE;
267 }
268 fmt = header_fmt_str;
269 } while (*++argv);
270
271 fflush_stdout_and_exit(retval);
272 }
273