Perl Device::SerialPort - linux

Question

Looking for right way to detect one keyword during board boot up message.
After keyword detected, send Enter key after one second.
Kernel is Linux.
# Serial port inisialisation is finished here.
# Read boot message
($count, $result) = $ob->read(300); # at least 300 chars coming till keyword appear
if ($result =~ m/Booting_up/) {
print "send Enter ...\n";
sleep 1;
$ob->write("\r\n");
}
Thanks for hint

Answer 1

It appears that you are using Win32::SerialPort module, or perhaps Device::SerialPort which
provides an object-based user interface essentially identical to the one provided by the Win32::SerialPort module.
Its method read takes the number of bytes to read and returns the number read and writes them into the given string.
You may be "missing" the phrase because it's past the 300-mark, and your code doesn't read any further. Try to loop, getting a few bytes at a time and adding them up, thus building the string in small reads.
my bytes_in = 10; # length of pattern, but it does NOT ensure anything
my ($read, $result);
while (1)
{
my ($count, $read) = $ob->read( $bytes_in );
$result = $result . $read;
if ($result =~ m/Booting_up/) { # is it "Booting_up" or "Booting up" ?
print "send Enter ...\n";
sleep 1; # is this needed?
$ob->write("\r\n");
# last; # in case this is all you need to do
}
last if $count != $bytes_in; # done reading
}
I don't put the $ob->read statement in the loop condition since the documentation isn't crystal clear on how the method works. You may also be able to simply use
while ( my ($count, $read) = $ob->read( $bytes_in ) ) {
$result = $result . $read;
if ($result =~ m/Booting_up/s) {
# ...
}
last if $count != $bytes_in;
}
We read a small number of bytes at a time to prevent problems with either polling or blocking reads, brought up in comments by BenPen. See Configuration and capability methods.
You can first read those first 300 bytes that precede the pattern in one go and then start reading a few (or one) at a time, which would also lead to the quickest identification of the phrase.
This can be tweaked further but let's first see what it does as it stands (I cannot test).
Documentation also offers a few other methods which may be useful, in particular readline and streamline. As this is all rather low level there are yet other ways but if you got all else working perhaps this will be enough to complete it.

Answer 2

Perhaps rather index the string?
($count, $result) = $ob->read(300); # at least 300 chars coming till keyword appear
$substring = 'Booting_up';
if (index($result, $substring) != -1) {
print "send Enter ..\n";
sleep 1;
$ob->write("\r\n");
}