Attempts to read LENGTH characters of data into variable SCALAR from the specified FILEHANDLE. Returns the number of characters actually read, 0 at end of file, or undef if there was an error. SCALAR will be grown or shrunk to the length actually read. If SCALAR needs growing, the new bytes will be zero bytes. An OFFSET may be specified to place the read data into some other place in SCALAR than the beginning. The call is actually implemented in terms of either Perl's or system's fread() call. To get a true read(2) system call, see sysread.
Note the characters: depending on the status of the filehandle, either (8-bit) bytes or characters are read. By default all filehandles operate on bytes, but for example if the filehandle has been opened with the :utf8 I/O layer (see "open", and the open pragma, open), the I/O will operate on characters, not bytes.