103 lines
4.0 KiB
C
103 lines
4.0 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Copyright (C) 2017 Denys Vlasenko <vda.linux@googlemail.com>
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*
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* Licensed under GPLv2, see file LICENSE in this source tree.
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*/
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//config:config FALLOCATE
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//config: bool "fallocate (4.1 kb)"
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//config: default y
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//config: help
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//config: Preallocate space for files.
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//applet:IF_FALLOCATE(APPLET(fallocate, BB_DIR_USR_BIN, BB_SUID_DROP))
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//kbuild:lib-$(CONFIG_FALLOCATE) += fallocate.o
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//usage:#define fallocate_trivial_usage
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//usage: "[-o OFS] -l LEN FILE"
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// fallocate [-c|-p|-z] [-n] [-o OFS] -l LEN FILE
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// fallocate -d [-o OFS] [-l LEN] FILE
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//usage:#define fallocate_full_usage "\n\n"
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//usage: "Preallocate space for FILE\n"
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// "\n -c Remove range"
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// "\n -p Make hole"
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// "\n -z Zero and allocate range"
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// "\n -d Convert zeros to holes"
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// "\n -n Keep size"
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//usage: "\n -o OFS Offset of range"
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//usage: "\n -l LEN Length of range"
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//Upstream options:
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//The options --collapse-range, --dig-holes, --punch-hole and --zero-range
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//are mutually exclusive.
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//-c, --collapse-range
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// Removes a byte range from a file, without leaving a hole. The byte range
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// to be collapsed starts at offset and continues for length bytes.
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// At the completion of the operation, the contents of the file starting
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// at the location offset+length will be appended at the location offset,
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// and the file will be length bytes smaller. The option --keep-size may
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// not be specified for the collapse-range operation.
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//-d, --dig-holes
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// Detect and dig holes. This makes the file sparse in-place, without using
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// extra disk space. The minimum size of the hole depends on filesystem I/O
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// block size (usually 4096 bytes). Also,
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//-l, --length length
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// Specifies the length of the range, in bytes.
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//-n, --keep-size
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// Do not modify the apparent length of the file. This may effectively
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// allocate blocks past EOF, which can be removed with a truncate.
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//-o, --offset offset
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// Specifies the beginning offset of the range, in bytes.
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//-p, --punch-hole
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// Deallocates space (i.e., creates a hole) in the byte range starting
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// at offset and continuing for length bytes. Within the specified range,
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// partial filesystem blocks are zeroed, and whole
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// filesystem blocks are removed from the file. After a successful call,
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// subsequent reads from this range will return zeroes. This option may not
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// be specified at the same time as the
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// --zero-range option. Also, when using this option, --keep-size is implied.
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//-z, --zero-range
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// Zeroes space in the byte range starting at offset and continuing for
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// length bytes. Within the specified range, blocks are preallocated for
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// the regions that span the holes in the file. After
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// a successful call, subsequent reads from this range will return zeroes.
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// Zeroing is done within the filesystem preferably by converting the range
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// into unwritten extents. This approach means that the specified range
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// will not be physically zeroed out on the device (except for partial
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// blocks at the either end of the range), and I/O is (otherwise) required
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// only to update metadata.
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// Option --keep-size can be specified to prevent file length modification.
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#include "libbb.h"
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int fallocate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int fallocate_main(int argc UNUSED_PARAM, char **argv)
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{
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const char *str_l;
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const char *str_o = "0";
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off_t ofs, len;
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unsigned opts;
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int fd;
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/* exactly one non-option arg */
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opts = getopt32(argv, "^" "l:o:" "\0" "=1", &str_l, &str_o);
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if (!(opts & 1))
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bb_show_usage();
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ofs = xatoull_sfx(str_o, kmg_i_suffixes);
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len = xatoull_sfx(str_l, kmg_i_suffixes);
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argv += optind;
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fd = xopen3(*argv, O_RDWR | O_CREAT, 0666);
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/* posix_fallocate has unusual method of returning error */
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/* maybe use Linux-specific fallocate(int fd, int mode, off_t offset, off_t len) instead? */
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if ((errno = posix_fallocate(fd, ofs, len)) != 0)
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bb_perror_msg_and_die("fallocate '%s'", *argv);
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/* util-linux also performs fsync(fd); */
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return EXIT_SUCCESS;
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}
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