POSIX_FALLOCATE

Section: Linux Programmer's Manual (3)
Updated: 2015-03-02
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NAME

posix_fallocate - allocate file space

SYNOPSIS

#include <fcntl.h>

int posix_fallocate(int fd, off_t offset, off_t len);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

posix_fallocate():

: _XOPEN_SOURCE >= 600 || _POSIX_C_SOURCE >= 200112L

DESCRIPTION

The function posix_fallocate() ensures that disk space is allocated for the file referred to by the descriptor fd for the bytes in the range starting at offset and continuing for len bytes. After a successful call to posix_fallocate(), subsequent writes to bytes in the specified range are guaranteed not to fail because of lack of disk space.

If the size of the file is less than offset+len, then the file is increased to this size; otherwise the file size is left unchanged.

RETURN VALUE

posix_fallocate() returns zero on success, or an error number on failure. Note that errno is not set.

ERRORS

EBADF: fd is not a valid file descriptor, or is not opened for writing.
EFBIG: offset+len exceeds the maximum file size.
EINVAL: offset was less than 0, or len was less than or equal to 0.
ENODEV: fd does not refer to a regular file.
ENOSPC: There is not enough space left on the device containing the file referred to by fd.
ESPIPE: fd refers to a pipe.

VERSIONS

posix_fallocate() is available since glibc 2.1.94.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
posix_fallocate()	Thread safety	MT-Safe

CONFORMING TO

POSIX.1-2001.

POSIX.1-2008 says that an implementation shall give the EINVAL error if len was 0, or offset was less than 0. POSIX.1-2001 says that an implementation shall give the EINVAL error if len is less than 0, or offset was less than 0, and may give the error if len equals zero.

NOTES

In the glibc implementation, posix_fallocate() is implemented using fallocate(2).

COLOPHON

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