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path: root/coreutils/head.c (plain)
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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
58static void
59print_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
75static void
76print_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
104static void
105print_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 */
140void print_except_N_last_bytes(FILE *fp, unsigned count);
141void 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
147static unsigned long
148eat_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
159static 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
168int head_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
169int 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
generated by cgit at 2024-05-16 02:14:44 (GMT)