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/* vi: set sw=4 ts=4: */
/*
* head implementation for busybox
*
* Copyright (C) 2003 Manuel Novoa III <mjn3@codepoet.org>
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
/* BB_AUDIT SUSv3 compliant */
/* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
/* http://www.opengroup.org/onlinepubs/007904975/utilities/head.html */
//kbuild:lib-$(CONFIG_HEAD) += head.o
//usage:#define head_trivial_usage
//usage: "[OPTIONS] [FILE]..."
//usage:#define head_full_usage "\n\n"
//usage: "Print first 10 lines of each FILE (or stdin) to stdout.\n"
//usage: "With more than one FILE, precede each with a filename header.\n"
//usage: "\n -n N[kbm] Print first N lines"
//usage: IF_FEATURE_FANCY_HEAD(
//usage: "\n -n -N[kbm] Print all except N last lines"
//usage: "\n -c [-]N[kbm] Print first N bytes"
//usage: "\n -q Never print headers"
//usage: "\n -v Always print headers"
//usage: )
//usage: "\n"
//usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
//usage:
//usage:#define head_example_usage
//usage: "$ head -n 2 /etc/passwd\n"
//usage: "root:x:0:0:root:/root:/bin/bash\n"
//usage: "daemon:x:1:1:daemon:/usr/sbin:/bin/sh\n"
#include "libbb.h"
/* This is a NOEXEC applet. Be very careful! */
#if !ENABLE_FEATURE_FANCY_HEAD
# define print_first_N(fp,count,bytes) print_first_N(fp,count)
#endif
static void
print_first_N(FILE *fp, unsigned long count, bool count_bytes)
{
#if !ENABLE_FEATURE_FANCY_HEAD
const int count_bytes = 0;
#endif
while (count) {
int c = getc(fp);
if (c == EOF)
break;
if (count_bytes || (c == '\n'))
--count;
putchar(c);
}
}
#if ENABLE_FEATURE_FANCY_HEAD
static void
print_except_N_last_bytes(FILE *fp, unsigned count)
{
unsigned char *circle = xmalloc(++count);
unsigned head = 0;
for(;;) {
int c;
c = getc(fp);
if (c == EOF)
goto ret;
circle[head++] = c;
if (head == count)
break;
}
for (;;) {
int c;
if (head == count)
head = 0;
putchar(circle[head]);
c = getc(fp);
if (c == EOF)
goto ret;
circle[head] = c;
head++;
}
ret:
free(circle);
}
static void
print_except_N_last_lines(FILE *fp, unsigned count)
{
char **circle = xzalloc((++count) * sizeof(circle[0]));
unsigned head = 0;
for(;;) {
char *c;
c = xmalloc_fgets(fp);
if (!c)
goto ret;
circle[head++] = c;
if (head == count)
break;
}
for (;;) {
char *c;
if (head == count)
head = 0;
fputs(circle[head], stdout);
c = xmalloc_fgets(fp);
if (!c)
goto ret;
free(circle[head]);
circle[head++] = c;
}
ret:
head = 0;
for(;;) {
free(circle[head++]);
if (head == count)
break;
}
free(circle);
}
#else
/* Must never be called */
void print_except_N_last_bytes(FILE *fp, unsigned count);
void print_except_N_last_lines(FILE *fp, unsigned count);
#endif
#if !ENABLE_FEATURE_FANCY_HEAD
# define eat_num(negative_N,p) eat_num(p)
#endif
static unsigned long
eat_num(bool *negative_N, const char *p)
{
#if ENABLE_FEATURE_FANCY_HEAD
if (*p == '-') {
*negative_N = 1;
p++;
}
#endif
return xatoul_sfx(p, bkm_suffixes);
}
static const char head_opts[] ALIGN1 =
"n:"
#if ENABLE_FEATURE_FANCY_HEAD
"c:qv"
#endif
;
#define header_fmt_str "\n==> %s <==\n"
int head_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int head_main(int argc, char **argv)
{
unsigned long count = 10;
#if ENABLE_FEATURE_FANCY_HEAD
int header_threshhold = 1;
bool count_bytes = 0;
bool negative_N = 0;
#else
# define header_threshhold 1
# define count_bytes 0
# define negative_N 0
#endif
FILE *fp;
const char *fmt;
char *p;
int opt;
int retval = EXIT_SUCCESS;
#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
/* Allow legacy syntax of an initial numeric option without -n. */
if (argv[1] && argv[1][0] == '-'
&& isdigit(argv[1][1])
) {
--argc;
++argv;
p = argv[0] + 1;
goto GET_COUNT;
}
#endif
/* No size benefit in converting this to getopt32 */
while ((opt = getopt(argc, argv, head_opts)) > 0) {
switch (opt) {
#if ENABLE_FEATURE_FANCY_HEAD
case 'q':
header_threshhold = INT_MAX;
break;
case 'v':
header_threshhold = -1;
break;
case 'c':
count_bytes = 1;
/* fall through */
#endif
case 'n':
p = optarg;
#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
GET_COUNT:
#endif
count = eat_num(&negative_N, p);
break;
default:
bb_show_usage();
}
}
argc -= optind;
argv += optind;
if (!*argv)
*--argv = (char*)"-";
fmt = header_fmt_str + 1;
if (argc <= header_threshhold) {
#if ENABLE_FEATURE_FANCY_HEAD
header_threshhold = 0;
#else
fmt += 11; /* "" */
#endif
}
if (negative_N) {
if (count >= INT_MAX / sizeof(char*))
bb_error_msg("count is too big: %lu", count);
}
do {
fp = fopen_or_warn_stdin(*argv);
if (fp) {
if (fp == stdin) {
*argv = (char *) bb_msg_standard_input;
}
if (header_threshhold) {
printf(fmt, *argv);
}
if (negative_N) {
if (count_bytes) {
print_except_N_last_bytes(fp, count);
} else {
print_except_N_last_lines(fp, count);
}
} else {
print_first_N(fp, count, count_bytes);
}
die_if_ferror_stdout();
if (fclose_if_not_stdin(fp)) {
bb_simple_perror_msg(*argv);
retval = EXIT_FAILURE;
}
} else {
retval = EXIT_FAILURE;
}
fmt = header_fmt_str;
} while (*++argv);
fflush_stdout_and_exit(retval);
}
|
