sysread

sysread filehandle, scalar, length, [offset]

Reads length bytes of data into variable scalar from the specified filehandle. The function returns the number of bytes actually read, or 0 at EOF. It returns the undefined value on error. scalar will grow or shrink to the length actually read. The offset, if specified, says where in the string to start putting the bytes, so that you can read into the middle of a string that's being used as a buffer. You should be prepared to handle the problems (like interrupted system calls) that standard I/O normally handles for you.