posix_fallocate(2) [freebsd man page]
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 guaranteed to be allocated upon successful return. That is, if 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 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 setting 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 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 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 <mdf@FreeBSD.org>. BSD
January 23, 2014 BSD
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posix_fallocate(3C) Standard C Library Functions posix_fallocate(3C) NAME
posix_fallocate - file space control SYNOPSIS
#include <fcntl.h> int posix_fallocate(int fd, off_t offset, off_t len); DESCRIPTION
The posix_fallocate() function ensures 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 will 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() adjusts the file size to offset+len. Otherwise, the file size is not changed. Space allocated with posix_fallocate() is freed by a successful call to creat(2) or open(2) that truncates the size of the file. Space allocated with posix_fallocate() may be freed by a successful call to ftruncate(3C) that reduces the file size to a size smaller than off- set+len. RETURN VALUES
Upon successful completion, posix_fallocate() returns zero. Otherwise, an error number is returned to indicate the error. ERRORS
The posix_fallocate() function will fail if: EBADF The fd argument is not a valid file descriptor or 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 or equal to 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. USAGE
The posix_fallocate() function has a transitional interface for 64-bit file offsets. See lf64(5). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Committed | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ |Standard |See standards(5). | +-----------------------------+-----------------------------+ SEE ALSO
creat(2), open(2), unlink(2), ftruncate(3C), attributes(5), standards(5) SunOS 5.11 14 Jul 2008 posix_fallocate(3C)