perl function sysread

The sysread function in Perl reads a specified number of bytes from a file or a filehandle and returns the number of bytes actually read. This function provides a lower-level interface to read data from a filehandle than the standard read function.

Here is an example of how to use the sysread function to read a file:

open(my $fh, '<', 'file.txt') or die "Cannot open file: $!";
my $buffer;
my $bytes_read = sysread($fh, $buffer, 1024); # read up to 1024 bytes
if (!defined($bytes_read)) {
    die "Error reading file: $!";
}
print "Read $bytes_read bytes: $buffer\n";
close($fh);

In this example, we first open the file "file.txt" for reading using the open function. We then declare a scalar variable $buffer to hold the data read from the file, and call sysread to read up to 1024 bytes from the filehandle $fh. The actual number of bytes read is returned in the $bytes_read variable. If an error occurs, sysread returns undef, so we check for that and die with an error message. Finally, we print out the number of bytes read and the contents of the buffer, and close the filehandle.