The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.
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posix_fallocate - file space control (ADVANCED REALTIME)


[ADV] [Option Start] #include <fcntl.h>

int posix_fallocate(int
fd, off_t offset, off_t len); [Option End]


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.


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


The posix_fallocate() function shall fail if:

The fd argument is not a valid file descriptor.
The fd argument references a file that was opened without write permission.
The value of offset+ len is greater than the maximum file size.
A signal was caught during execution.
The len argument was zero or the offset argument was less than zero.
An I/O error occurred while reading from or writing to a file system.
The fd argument does not refer to a regular file.
There is insufficient free space remaining on the file system storage media.
The fd argument is associated with a pipe or FIFO.

The following sections are informative.




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






creat(), ftruncate(), open(), unlink(), the Base Definitions volume of IEEE Std 1003.1-2001, <fcntl.h>


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.

End of informative text.

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