posix_fallocate Subroutine
Purpose
Reserve storage space for a given file descriptor.
Syntax
#include <fcntl.h>
int posix_fallocate (int fd, off_t offset, off_t len);Description
This function reserves adequate space on the file system for the file data range beginning at the value specified by the offset parameter and continuing for the number of bytes specified by the len parameter. Upon successful return, subsequent writes to this file data range will not fail due to lack of free space on the file system media. Space allocated by the posix_fallocate subroutine can be freed by a successful call to the creat subroutine or open subroutine, or by the ftruncate subroutine, which truncates the file size to a size smaller than the sum of the offset parameter and the len parameter.
Parameters
| Item | Description |
|---|---|
| fd | File descriptor of the file to reserve |
| offset | Represents the beginning of the address range |
| len | Determines the length of the address range |
Return Values
Upon
successful completion, the posix_fallocate subroutine returns 0.
Otherwise, one of the following error codes will be returned.
Error Codes
| Item | Description |
|---|---|
| EBADF | The fd parameter is not a valid file descriptor |
| EBADF | The fd parameter references a file that was opened without write permission. |
| EFBIG | The value of the offset parameter plus the len parameter is greater than the maximum file size |
| EINTR | A signal was caught during execution |
| EIO | An I/O error occurred while reading from or writing to a file system |
| ENODEV | The fd parameter does not refer to a regular file. |
| EINVAL | The value of the advice parameter is invalid. |
| ENOSPC | There is insufficient free space remaining on the file system storage media |
| ESPIPE | The fd parameter is associated with a pipe of FIFO |
| ENOTSUP | The underlying file system is not supported |