NAME

posix_fallocate - file space control (ADVANCED REALTIME)

SYNOPSIS

[ADV] #include <fcntl.h>

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

DESCRIPTION

The posix_fallocate() function shall ensure that any required storage for regular file data starting at offset and continuing for len bytes is allocated on the file system storage media. If posix_fallocate() returns successfully, subsequent writes to the specified file data shall not fail due to the lack of free space on the file system storage media.

If the offset+ len is beyond the current file size, then posix_fallocate() shall adjust the file size to offset+ len. Otherwise, the file size shall not be changed.

It is implementation-defined whether a previous posix_fadvise() call influences allocation strategy.

Space allocated via posix_fallocate() shall be freed by a successful call to creat() or open() that truncates the size of the file. Space allocated via posix_fallocate() may be freed by a successful call to ftruncate() that reduces the file size to a size smaller than offset+ len.

RETURN VALUE

Upon successful completion, posix_fallocate() shall return zero; otherwise, an error number shall be returned to indicate the error.

ERRORS

The posix_fallocate() function shall fail if:

[EBADF]

The fd argument is not a valid file descriptor.

[EBADF]

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

[EFBIG]

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

[EINTR]

A signal was caught during execution.

[EINVAL]

The len argument is less than zero, or the offset argument is less than zero, or the underlying file system does not support this operation.

[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.

The posix_fallocate() function may fail if:

[EINVAL]

The len argument is zero.

EXAMPLES

None.

APPLICATION USAGE

The posix_fallocate() function is part of the Advisory Information option and need not be provided on all implementations.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

creat, ftruncate, open, unlink

XBD <fcntl.h>

CHANGE HISTORY

First released in Issue 6. Derived from IEEE Std 1003.1d-1999.

In the SYNOPSIS, the inclusion of <sys/types.h> is no longer required.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/69 is applied, changing the function prototype in the SYNOPSIS section. The previous prototype was not large file-aware, and the standard developers felt it acceptable to make this change before implementations of this function become widespread.

Issue 7

Austin Group Interpretations 1003.1-2001 #022, #024, and #162 are applied, changing the definition of the [EINVAL] error.