sys.seek_key()

Purpose:

sys.seek_key() prepares for sequential reading by seeking to either the start or end key position.

Usage:

ret = sys.seek_key(<asfile>,<keyno>,<seektype>);

Arguments:

<asfile> - asfile

integer <keyno> - An integer returned by a call to sys.get_keyno()

integer <seektype> - Either SEEK_START or SEEK_END

Returns:

0 - OK

-1 - Some Error

Where Used:

sys.seek_key() will typically be called after calls to sys.set_skey() and sys.set_ekey() and before calling sys.read_file(...,F_SEQNEXT)

Example:

See the demo.seekkey.1 demo program for an example.

Description:

sys.seek_key() prepares a file for reading sequentially. If the start key set by a call to sys.set_skey() is greater than the end key set by a call to sys.set_skey(), or if the <seektype> is SEEK_END, sys.seek_key() reverses the meaning of F_SEQNEXT and F_SEQPREV for sequential reads that follow. You almost always should use F_SEQNEXT when reading a file sequentially after a call to sys.seek_key().

F_DRNEXT and F_DRPREV can be used in place of F_SEQNEXT and F_SEQPREV and are better alternatives because you do not need to specify the key that you are reading by. They will always use the key specified in the <keyno> arg.

Bugs/Features/Comments:

When using sys.seek_key() on secondary keys, you still need to specify the keyno in calls to sys.read_file(...,F_SEQNEXT) So use F_DRNEXT and F_DRPREV instead.

Be very careful using F_SEQPREV after calling sys.seek_key(). It may actually read the next rcd rather than the previous.

See Also:

sys.set_skey()

sys.set_ekey()

sys.read_file()