Raspi_Perl_Notes

Then, you can include the code below in a script:

#!/usr/bin/perl -w

use strict;

BEGIN{

push @INC,"/usr/lib/perl5/";

}

use lib '/usr/lib/perl5/Device';

use Device::SerialPort;

my $port = Device::SerialPort->new("/dev/ttyAMA0");

$port->baudrate(9600);

$port->databits(8);

$port->parity("none");

$port->stopbits(1);

# to write:

$port->write("stuff to write\n");

# to read:

$char=$port->lookfor();

if($char){

print "Got stuff: $char\n";

}

Getting the command line in a Perl script:

use strict;

use FindBin;

use Cwd 'abs_path';

my $cmdfile = abs_path(__FILE__);

my $scriptname;

$scriptname=$cmdfile;

$scriptname=~s/.*\///; # chomp off path

my $cpath=$cmdfile;

$cpath=~s/\/[^\/]+$//; # get just the path to the command file

Perl timer functions with higher resolution than 1 second:

#!/usr/bin/perl

use strict;

use warnings;

use Time::HiRes qw(usleep nanosleep);

# 1 millisecond == 1000 microseconds

usleep(1000);

# 1 microsecond == 1000 nanoseconds

nanosleep(1000000);

Socket Communications over TCP:

http://xmodulo.com/how-to-write-simple-tcp-server-and-client-in-perl.html

In this example, client connects to a server with well-known IP address and port. Once client is connected to the server, it sends data to the server, and waits for a reply. Upon receiving data from client, server responds with an acknowledgement message.

The purpose of shutdown(SOCKET, 1) in the example is to tell the other end that you have finished sending data, without closing SOCKET. Note that you can still receive data afterward.

TCP server example in Perl

use IO::Socket::INET;

# auto-flush on socket

$| = 1;

# creating a listening socket

my $socket = new IO::Socket::INET (

LocalHost => '0.0.0.0',

LocalPort => '7777',

Proto => 'tcp',

Listen => 5,

Reuse => 1

);

die "cannot create socket $!\n" unless $socket;

print "server waiting for client connection on port 7777\n";

while(1)

{

# waiting for a new client connection

my $client_socket = $socket->accept();

# get information about a newly connected client

my $client_address = $client_socket->peerhost();

my $client_port = $client_socket->peerport();

print "connection from $client_address:$client_port\n";

# read up to 1024 characters from the connected client

my $data = "";

$client_socket->recv($data, 1024);

print "received data: $data\n";

# write response data to the connected client

$data = "ok";

$client_socket->send($data);

# notify client that response has been sent

shutdown($client_socket, 1);

}

$socket->close();

TCP client example in Perl

use IO::Socket::INET;

# auto-flush on socket

$| = 1;

# create a connecting socket

my $socket = new IO::Socket::INET (

PeerHost => '192.168.1.10',

PeerPort => '7777',

Proto => 'tcp',

);

die "cannot connect to the server $!\n" unless $socket;

print "connected to the server\n";

# data to send to a server

my $req = 'hello world';

my $size = $socket->send($req);

print "sent data of length $size\n";

# notify server that request has been sent

shutdown($socket, 1);

# receive a response of up to 1024 characters from server

my $response = "";

$socket->recv($response, 1024);

print "received response: $response\n";

$socket->close();

TIME - EPOCH conversions:

See code below for sample of how to do epoch to date and back...

#!/usr/intel/bin/perl

$|=1; # turns off buffering

## This is a simple script to demonstrate using localtime and timelocal

## functions to convert a datestamp to epoch and back.

## The time(); function is used to get the current epoch time.

## use Time::localtime; ### DO NOT USE Time::localtime - it will return

## a *structure*(?) from the localtime function

use Time::Local; ## required for the 'timelocal' function to convert

## an array to an epoch time

my $i,j,k,e;

my @weekday = qw(Sun, Mon, Tues, Wed, Thu, Fri, Sat);

my $sec, $min, $hour, $mday, $mon, $year, $wday, $yday, $isdst;

$e=time();

print "local time epoch: $e\n";

($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime($e);

$year = $year + 1900;

$mon += 1;

print "Formated time = $mday/$mon/$year $hour:$min:$sec $weekday[$wday]\n";

print "\nDo it again...\n";

$e+=3742;

($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime($e);

$year = $year + 1900;

$mon += 1;

print "Formated time = $mday/$mon/$year $hour:$min:$sec $weekday[$wday]\n\n";

## now convert back...

$year=2018;

$mon=5;

$mday=28;

$hour=13;

$min=37;

$sec=51;

$j=timelocal($sec,$min,$hour,$mday,$mon,$year);

print "Epoch time is: $j\n";

# convert forward...

($sec,$min,$hour,$mday,$mon,$year) = (localtime($j))[0,1,2,3,4,5];

$year = $year + 1900;

$mon += 1;

print "Printing scalar localtime of epoch: ";

print scalar localtime($j);

print "\nFormated time = $mon/$mday/$year $hour:$min:$sec \n";

SCP Stuff:

Copying files to your Raspberry Pi

Copy the file myfile.txt from your computer to the pi user's home folder of your Raspberry Pi at the IP address 192.168.1.3 with the following command:

scp myfile.txt pi@192.168.1.3:

Copy the file to the /home/pi/project/ directory on your Raspberry Pi (the project folder must already exist):

scp myfile.txt pi@192.168.1.3:project/

Copying files from your Raspberry Pi

Copy the file myfile.txt from your Raspberry Pi to the current directory on your other computer:

scp pi@192.168.1.3:myfile.txt .

Copying multiple files

Copy multiple files by separating them with spaces:

scp myfile.txt myfile2.txt pi@192.168.1.3:

Alternatively, use a wildcard to copy all files matching a particular search with:

scp *.txt pi@192.168.1.3:

(all files ending in .txt)

scp m* pi@192.168.1.3:

(all files starting with m)

scp m*.txt pi@192.168.1.3:

(all files starting with m and ending in .txt)

Filenames with spaces

Note that some of the examples above will not work for file names containing spaces. Names like this need to be encased in quotes:

scp "my file.txt" pi@192.168.1.3:

See this page for info on ssh keys: https://www.raspberrypi.org/documentation/remote-access/ssh/passwordless.md