=over =item seek FILEHANDLE,POSITION,WHENCE X<seek> X<fseek> X<filehandle, position> Sets FILEHANDLE's position, just like the L<fseek(3)> call of C C<stdio>. FILEHANDLE may be an expression whose value gives the name of the filehandle. The values for WHENCE are C<0> to set the new position I<in bytes> to POSITION; C<1> to set it to the current position plus POSITION; and C<2> to set it to EOF plus POSITION, typically negative. For WHENCE you may use the constants C<SEEK_SET>, C<SEEK_CUR>, and C<SEEK_END> (start of the file, current position, end of the file) from the L<Fcntl> module. Returns C<1> on success, false otherwise. Note the emphasis on bytes: even if the filehandle has been set to operate on characters (for example using the C<:encoding(UTF-8)> I/O layer), the L<C<seek>|/seek FILEHANDLE,POSITION,WHENCE>, L<C<tell>|/tell FILEHANDLE>, and L<C<sysseek>|/sysseek FILEHANDLE,POSITION,WHENCE> family of functions use byte offsets, not character offsets, because seeking to a character offset would be very slow in a UTF-8 file. If you want to position the file for L<C<sysread>|/sysread FILEHANDLE,SCALAR,LENGTH,OFFSET> or L<C<syswrite>|/syswrite FILEHANDLE,SCALAR,LENGTH,OFFSET>, don't use L<C<seek>|/seek FILEHANDLE,POSITION,WHENCE>, because buffering makes its effect on the file's read-write position unpredictable and non-portable. Use L<C<sysseek>|/sysseek FILEHANDLE,POSITION,WHENCE> instead. Due to the rules and rigors of ANSI C, on some systems you have to do a seek whenever you switch between reading and writing. Amongst other things, this may have the effect of calling stdio's L<clearerr(3)>. A WHENCE of C<1> (C<SEEK_CUR>) is useful for not moving the file position: seek($fh, 0, 1); This is also useful for applications emulating C<tail -f>. Once you hit EOF on your read and then sleep for a while, you (probably) have to stick in a dummy L<C<seek>|/seek FILEHANDLE,POSITION,WHENCE> to reset things. The L<C<seek>|/seek FILEHANDLE,POSITION,WHENCE> doesn't change the position, but it I<does> clear the end-of-file condition on the handle, so that the next C<readline FILE> makes Perl try again to read something. (We hope.) If that doesn't work (some I/O implementations are particularly cantankerous), you might need something like this: for (;;) { for ($curpos = tell($fh); $_ = readline($fh); $curpos = tell($fh)) { # search for some stuff and put it into files } sleep($for_a_while); seek($fh, $curpos, 0); } =back