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# PR_Seek64
Moves the current read-write file pointer by an offset expressed as a
64-bit integer.
## Syntax
```{code}
#include <prio.h>
PRInt64 PR_Seek64(
PRFileDesc *fd,
PRInt64 offset,
PRSeekWhence whence);
```
### Parameters
The function has the following parameters:
`fd`
: A pointer to a {ref}`PRFileDesc` object.
`offset`
: A value, in bytes, used with the whence parameter to set the file
pointer. A negative value causes seeking in the reverse direction.
`whence`
: A value of type {ref}`PRSeekWhence` that specifies how to interpret the
`offset` parameter in setting the file pointer associated with the
fd parameter. The value for the `whence` parameter can be one of
the following:
> - `PR_SEEK_SET`. Sets the file pointer to the value of the
> `offset` parameter.
> - `PR_SEEK_CUR`. Sets the file pointer to its current location
> plus the value of the `offset` parameter.
> - `PR_SEEK_END`. Sets the file pointer to the size of the file
> plus the value of the `offset` parameter.
### Returns
The function returns one of the following values:
- If the function completes successfully, it returns the resulting file
pointer location, measured in bytes from the beginning of the file.
- If the function fails, the file pointer remains unchanged and the
function returns -1. The error code can then be retrieved with
{ref}`PR_GetError`.
## Description
This is the idiom for obtaining the current location (expressed as a
64-bit integer) of the file pointer for the file descriptor `fd`:
`PR_Seek64(fd, 0, PR_SEEK_CUR)`
If the operating system can handle only a 32-bit file offset,
{ref}`PR_Seek64` may fail with the error code `PR_FILE_TOO_BIG_ERROR` if
the `offset` parameter is out of the range of a 32-bit integer.
## See Also
{ref}`PR_Seek`