Attempts to write LENGTH bytes of data from variable SCALAR to the
specified FILEHANDLE, using write(2). If LENGTH is
not specified, writes whole SCALAR. It bypasses buffered IO, so
mixing this with reads (other than sysread()), print, write,
seek, tell, or eof may cause confusion because the perlio and
stdio layers usually buffer data. Returns the number of bytes
actually written, or undef if there was an error (in this case the
errno variable $!
is also set). If the LENGTH is greater than the
data available in the SCALAR after the OFFSET, only as much data as is
available will be written.
An OFFSET may be specified to write the data from some part of the string other than the beginning. A negative OFFSET specifies writing that many characters counting backwards from the end of the string. If SCALAR is of length zero, you can only use an OFFSET of 0.
WARNING: If the filehandle is marked :utf8
, Unicode characters
encoded in UTF-8 are written instead of bytes, and the LENGTH, OFFSET, and
return value of syswrite() are in (UTF8-encoded Unicode) characters.
The :encoding(...)
layer implicitly introduces the :utf8
layer.
Alternately, if the handle is not marked with an encoding but you
attempt to write characters with code points over 255, raises an exception.
See binmode, open, and the open pragma, open.