File position

Purpose: Set a position or get a current position for an open file.

 file-position file-id <file id> \
     ( set <position> ) | ( get <position> ) \
     [ status <status> ]

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file-position will set or get position for a file opened with open-file, where <file id> is an open file identifier.

If "set" clause is used, file position is set to <position> (with 0 being the first byte).

If "get" clause is used, file position is obtained in <position> (with 0 being the first byte).

<status> number in "status" clause will be GG_OKAY if set/get succeeded, GG_ERR_OPEN if file not open, or GG_ERR_POSITION if not.

Note that setting position past the last byte of file is okay for writing - in this case the bytes between the end of file and the <position> are filled with null-bytes when the write operation occurs.

Examples

Open file "testwrite" and set file byte position to 100, then obtain it later:

 open-file "testwrite" file-id nf
 file-position file-id nf set 100
 ...
 file-position file-id nf get pos

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