posix_fallocate (2)

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(The comments found at the beginning of the groff file "man2/posix_fallocate.2freebsd".)

NAME

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

LIBRARY

Lb libc

SYNOPSIS

In fcntl.h Ft int Fn posix_fallocate int fd off_t offset off_t len

DESCRIPTION

Required storage for the range Fa offset to Fa offset + Fa len in the file referenced by Fa fd is guaranteed to be allocated upon successful return. That is, if Fn posix_fallocate returns successfully, 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 Fa offset + Fa len is beyond the current file size, then Fn posix_fallocate will adjust the file size to Fa offset + Fa len . Otherwise, the file size will not be changed.

Space allocated by Fn 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 Fn posix_fallocate may be freed by a successful call to ftruncate(2) that reduces the file size to a size smaller than Fa offset + Fa len .

RETURN VALUES

If successful, Fn posix_fallocate returns zero. It returns an error on failure, without setting errno

ERRORS

Possible failure conditions:

Bq Er EBADF

The Fa fd argument is not a valid file descriptor.

Bq Er EBADF

The Fa fd argument references a file that was opened without write permission.

Bq Er EFBIG

The value of Fa offset + Fa len is greater than the maximum file size.

Bq Er EINTR

A signal was caught during execution.

Bq Er EINVAL

The Fa len argument was less than or equal to zero or the Fa offset argument was less than zero.

Bq Er EIO

An I/O error occurred while reading from or writing to a file system.

Bq Er ENODEV

The Fa fd argument does not refer to a regular file.

Bq Er ENOSPC

There is insufficient free space remaining on the file system storage media.

Bq Er ESPIPE

The Fa fd argument is associated with a pipe or FIFO.

SEE ALSO

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

STANDARDS

The Fn posix_fallocate system call conforms to St -p1003.1-2004 .

HISTORY

The Fn posix_fallocate function appeared in Fx 9.0 .

AUTHORS

Fn posix_fallocate and this manual page were initially written by An Matthew Fleming Aq mdf@FreeBSD.org .