seekoffset

Seekoffset is a term used in computing to describe the distance or position to move the read or write pointer within a data source when performing a seek operation. It is typically expressed as a numeric value representing an offset, usually in bytes, though some APIs allow other units. The precise meaning of seekoffset depends on the API, and it is often paired with an origin flag that indicates where the offset starts, such as the beginning of the data, the current position, or the end.

In POSIX and most C libraries, seeking is done with an offset and a whence or origin parameter. Although the standard call uses separate offset and origin arguments, some wrapper libraries or documentation refer to this parameter combination as seekoffset. In such contexts, the seekoffset parameter indicates the distance to move from the specified origin.

In practice seekoffset enables random-access I/O, fast-forwarding or rewinding streams, resuming from a known position, and implementing features like seeking within multimedia playback or large binary files. For example, a function call seek(data_source, seekoffset, origin) moves the current position to origin + seekoffset. Different environments may represent the origin using constants such as SEEK_SET, SEEK_CUR, or SEEK_END.

Limitations include that not all data sources support seeking; for non-seekable streams such as certain network protocols or compressed data, a seekoffset-based repositioning may be unsupported or require re-reading or decoding.

See also: seek, lseek, tell, offset, SEEK_SET, SEEK_CUR, SEEK_END.