SIMPLE SOLUTIONS

POSIX_FALLOCATE(2FREEBSD) - Linux man page online | System calls

Pre-allocate storage for a range in a file.

Chapter
January 23, 2014
POSIX_FALLOCATE(2) BSD System Calls Manual POSIX_FALLOCATE(2)

NAME

posix_fallocate — pre-allocate storage for a range in a file

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <fcntl.h> int posix_fallocate(int fd, off_t offset, off_t len);

DESCRIPTION

Required storage for the range offset to offset + len in the file referenced by fd is guar‐ anteed to be allocated upon successful return. That is, if posix_fallocate() returns suc‐ cessfully, subsequent writes to the specified file data will not fail due to lack of free space on the file system storage media. Any existing file data in the specified range is unmodified. If offset + len is beyond the current file size, then posix_fallocate() will adjust the file size to offset + len. Otherwise, the file size will not be changed. Space allocated by posix_fallocate() will be freed by a successful call to creat(2) or open(2) that truncates the size of the file. Space allocated via posix_fallocate() may be freed by a successful call to ftruncate(2) that reduces the file size to a size smaller than offset + len.

RETURN VALUES

If successful, posix_fallocate() returns zero. It returns an error on failure, without set‐ ting errno.

ERRORS

Possible failure conditions: [EBADF] The fd argument is not a valid file descriptor. [EBADF] The fd argument references a file that was opened without write permis‐ sion. [EFBIG] The value of offset + len is greater than the maximum file size. [EINTR] A signal was caught during execution. [EINVAL] The len argument was less than or equal to zero or the offset argument was less than zero. [EIO] An I/O error occurred while reading from or writing to a file system. [ENODEV] The fd argument does not refer to a regular file. [ENOSPC] There is insufficient free space remaining on the file system storage media. [ESPIPE] The fd argument is associated with a pipe or FIFO.

SEE ALSO

creat(2), ftruncate(2), open(2), unlink(2)

STANDARDS

The posix_fallocate() system call conforms to IEEE Std 1003.1-2004 (“POSIX.1”).

HISTORY

The posix_fallocate() function appeared in FreeBSD 9.0.

AUTHORS

posix_fallocate() and this manual page were initially written by Matthew Fleming <@FreeBSD.org>.
BSD January 23, 2014 BSD
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