Returns the current position in bytes for FILEHANDLE, or -1 on error. FILEHANDLE may be an expression whose value gives the name of the actual filehandle. If FILEHANDLE is omitted, assumes the file last read.
Note the in bytes: even if the filehandle has been set to
operate on characters (for example by using the
layer), tell() will return byte offsets, not character offsets (because
that would render seek() and tell() rather slow).
The return value of tell() for the standard streams like the STDIN depends on the operating system: it may return -1 or something else. tell() on pipes, fifos, and sockets usually returns -1.
There is no
sysseek(FH, 0, 1)
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.