busybox/coreutils/head.c
Denys Vlasenko f560422fa0 Big cleanup in config help and description
Redundant help texts (one which only repeats the description)
are deleted.

Descriptions and help texts are trimmed.

Some config options are moved, even across menus.

No config option _names_ are changed.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-01-10 14:58:54 +01:00

272 lines
5.7 KiB
C

/* 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.
*/
//config:config HEAD
//config: bool "head"
//config: default y
//config: help
//config: head is used to print the first specified number of lines
//config: from files.
//config:
//config:config FEATURE_FANCY_HEAD
//config: bool "Enable -c, -q, and -v"
//config: default y
//config: depends on HEAD
//applet:IF_HEAD(APPLET_NOEXEC(head, head, BB_DIR_USR_BIN, BB_SUID_DROP, head))
//kbuild:lib-$(CONFIG_HEAD) += head.o
/* BB_AUDIT SUSv3 compliant */
/* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
/* http://www.opengroup.org/onlinepubs/007904975/utilities/head.html */
//usage:#define head_trivial_usage
//usage: "[OPTIONS] [FILE]..."
//usage:#define head_full_usage "\n\n"
//usage: "Print first 10 lines of each FILE (or stdin) to stdout.\n"
//usage: "With more than one FILE, precede each with a filename header.\n"
//usage: "\n -n N[kbm] Print first N lines"
//usage: IF_FEATURE_FANCY_HEAD(
//usage: "\n -n -N[kbm] Print all except N last lines"
//usage: "\n -c [-]N[kbm] Print first N bytes"
//usage: "\n -q Never print headers"
//usage: "\n -v Always print headers"
//usage: )
//usage: "\n"
//usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
//usage:
//usage:#define head_example_usage
//usage: "$ 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);
}