Programming Perl, 4th Edition

tell

tell FILEHANDLE
tell

This function returns the current file position (in bytes, zero-based) for FILEHANDLE. Typically, this value will be fed to the seek function at some future time to get back to the current position. FILEHANDLE may be an expression giving the name of the actual filehandle or a reference to a filehandle object. If FILEHANDLE is omitted, the function returns the position of the file last read. File positions are meaningful only on regular files. Devices, pipes, and sockets have no file position.

Note the in bytes: even if the filehandle has been set to operate on characters (for example, by using the :encoding(utf8) open layer), tell still always returns byte offsets, not character offsets (because that would render seek and tell rather slow).

There is no systell function. Use sysseek(FH, 0, 1) for that. Seek seek for an example telling how to use tell.

Do not use tell (or other buffered I/O operations) on a filehandle that has been manipulated by sysread, syswrite, or sysseek. Those functions ignore the buffering, while tell does not.