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/* vi: set sw=4 ts=4: */
/*
* Copyright (C) 2017 Denys Vlasenko <vda.linux@googlemail.com>
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
//config:config FALLOCATE
//config: bool "fallocate"
//config: default y
//config: help
//config: Preallocate space for files.
//applet:IF_FALLOCATE(APPLET(fallocate, BB_DIR_USR_BIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_FALLOCATE) += fallocate.o
//usage:#define fallocate_trivial_usage
//usage: "[-o OFS] -l LEN FILE"
// fallocate [-c|-p|-z] [-n] [-o OFS] -l LEN FILE
// fallocate -d [-o OFS] [-l LEN] FILE
//usage:#define fallocate_full_usage "\n\n"
//usage: "Preallocate space for FILE\n"
// "\n -c Remove range"
// "\n -p Make hole"
// "\n -z Zero and allocate range"
// "\n -d Convert zeros to holes"
// "\n -n Keep size"
//usage: "\n -o OFS Offset of range"
//usage: "\n -l LEN Length of range"
//Upstream options:
//The options --collapse-range, --dig-holes, --punch-hole and --zero-range
//are mutually exclusive.
//-c, --collapse-range
// Removes a byte range from a file, without leaving a hole. The byte range
// to be collapsed starts at offset and continues for length bytes.
// At the completion of the operation, the contents of the file starting
// at the location offset+length will be appended at the location offset,
// and the file will be length bytes smaller. The option --keep-size may
// not be specified for the collapse-range operation.
//-d, --dig-holes
// Detect and dig holes. This makes the file sparse in-place, without using
// extra disk space. The minimum size of the hole depends on filesystem I/O
// block size (usually 4096 bytes). Also,
//-l, --length length
// Specifies the length of the range, in bytes.
//-n, --keep-size
// Do not modify the apparent length of the file. This may effectively
// allocate blocks past EOF, which can be removed with a truncate.
//-o, --offset offset
// Specifies the beginning offset of the range, in bytes.
//-p, --punch-hole
// Deallocates space (i.e., creates a hole) in the byte range starting
// at offset and continuing for length bytes. Within the specified range,
// partial filesystem blocks are zeroed, and whole
// filesystem blocks are removed from the file. After a successful call,
// subsequent reads from this range will return zeroes. This option may not
// be specified at the same time as the
// --zero-range option. Also, when using this option, --keep-size is implied.
//-z, --zero-range
// Zeroes space in the byte range starting at offset and continuing for
// length bytes. Within the specified range, blocks are preallocated for
// the regions that span the holes in the file. After
// a successful call, subsequent reads from this range will return zeroes.
// Zeroing is done within the filesystem preferably by converting the range
// into unwritten extents. This approach means that the specified range
// will not be physically zeroed out on the device (except for partial
// blocks at the either end of the range), and I/O is (otherwise) required
// only to update metadata.
// Option --keep-size can be specified to prevent file length modification.
#include "libbb.h"
int fallocate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int fallocate_main(int argc UNUSED_PARAM, char **argv)
{
const char *str_l;
const char *str_o = "0";
off_t ofs, len;
unsigned opts;
int fd;
/* exactly one non-option arg */
opt_complementary = "=1";
opts = getopt32(argv, "l:o:", &str_l, &str_o);
if (!(opts & 1))
bb_show_usage();
ofs = xatoull_sfx(str_o, kmg_i_suffixes);
len = xatoull_sfx(str_l, kmg_i_suffixes);
argv += optind;
fd = xopen3(*argv, O_RDWR | O_CREAT, 0666);
/* posix_fallocate has unusual method of returning error */
/* maybe use Linux-specific fallocate(int fd, int mode, off_t offset, off_t len) instead? */
if ((errno = posix_fallocate(fd, ofs, len)) != 0)
bb_perror_msg_and_die("fallocate '%s'", *argv);
/* util-linux also performs fsync(fd); */
return EXIT_SUCCESS;
}
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