Re: Unable to read the string
- From: rob.dixon@xxxxxxx (Rob Dixon)
- Date: Thu, 31 Jul 2008 20:14:48 +0100
Arun wrote:
Hi this is Arun here, i am new to perl.Here i am trying to read a
string from the serial port but i am not able to and this is my
program:
# Read serial port until message or timeout occurs
sub ReadPort($$$) {
(my $String, my $TimeOut, my $Display) = @_;
$ob->read_const_time($TimeOut); # Setup timeout value in mS
my $Reply = ""; # Initialize message
do {
($Count, $Result) = $ob->read(1); # Read serial port
$Reply .= $Result; # Build message
print "$Result" if ($Display); # Display messages if enabled
} while($Count > 0 and $Reply !~ m/$String/);
print "\n" if ($Display); # Put carriage return at end of
displayed output
if ($Reply !~ m/$String/) {
print "ERROR: Read timed out waiting for '$String' \n";
return(1);
}
return($Reply);
You shouldn't use prototypes for Perl subroutines: they don't do what you think
they do, and they are more likely to break things than be useful.
Unless you have your own reasons for naming your variables with mixed case, many
people would thank you if you changed to using all lower-case. Names beginning
with a capital letter are usually package or module names.
What problem are you having? It looks basically alright to me, although it may
not be wise to use the value of $result if $count is zero. How about a loop like
this:
{
my ($count, $result) = $ob->read(1);
last unless $count;
print $result if $display;
$reply .= $result;
redo unless $reply =~ /\Q$string/;
}
HTH,
Rob
.
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