Daily Archives: March 13, 2019

Getting CGI and Perl scripts up and running on Minimal Ubuntu

Linux, Raspberry Pi, Web Hosting, , , , ,

I was trying, again to get this up and running. I have a piece of code notestack-example.cgi that uses Perl and the Perl Module for CGI. I had this working after fiddling with it the first time I flashed the SD card that I set up for a Pine 64 that was set up with minimal Ubuntu Xenial.

The problem is I wrote down only sketchy instructions and had to re-figure it out. After flashing another card, the first one had a slow moving corruption that would cause the machine to halt after a while, I got more clear with the process.

I have posted it here for myself, if I get stuck again and for anyone else who might need to know the process, if they get stuck. It is a rough outline. I copied what commands I issued from the history and added comments and some test code that I had on a RaspberryPi which has been running the notestack-example.cgi among other items for years so that was my baseline.

Outline getting CGI and Perl running for Apache

In this outline it is assumed that Apache2 is installed and configured.

Optional: To make it easier to get to the cgi directory from your home, create a symlink in the user home directory to be able to move into the cgi folder easier.

ln -s /usr/lib/cgi-bin cgi

Enable CGI support for Apache…
sudo a2enmod cgi

modify /etc/apache2/sites-enabled/000-default.conf

Putting in the code that enables cgi in the Apache config file for sites, this was take from the Raspberrypi and added into /etc/apache2/sites-enabled/000-default.conf
it was put right above the </VirtualHost> line.

——————————————————
ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
<Directory “/usr/lib/cgi-bin”>
AllowOverride None
Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
Order allow,deny
Allow from all
</Directory>

——————————————————

Test with a simple BASH CGI script

Use the following code as printenv.cgi to test basic CGI with a bash script.
in the /usr/lib/cgi-bin directory.
——————————————————
#!/bin/bash -f
echo “Content-type: text/html”
echo “”
echo “<PRE>”
env || printenv
echo “</PRE>”
exit 0
——————————————————

test with…
which needs to be 755 (+x) permissions. This file is from the RPI, was used years ago to test it out.

sudo nano printenv.cgi
sudo chmod +x printenv.cgi
  /printenv.cgi
If all is well this will also be accessible from the web…
curl http://localhost/cgi-bin/printenv.cgi

curl is installed in the minimal build.

If you are using this on your own intranet OK, if this machine is accessible from the web get rid of printenv.cgi so the whole world can’t see the output if it gets found.

 

Test Perl

Test Perl scripts, normally Perl is installed even in the minimal Ubuntu build. It’s
presence can be tested for by using ‘which perl‘.
Use the following code as perl-test.cgi
in the /usr/lib/cgi-bin directory.
——————————————————
#!/usr/bin/perl
print “Content-type: text/html\n\n”;
print “Hello CGI\n”;
EOF
——————————————————

sudo nano perl-test.cgi
 sudo chmod 755 perl-test.cgi
 ./perl-test.cgi

Does it work via Apache?
  curl http://localhost/cgi-bin/perl-test.cgi

Perl CGI Module

Get Perl scripts (Any Perl code that uses CGI.pm in it) running and web accessible, ones that require the CGI Perl Module…

Got ERROR #1,missing CGI.pm, followed by #2 complained about a missing Util.pm, see below.

Got this error when the Perl Module was missing got a similar error after installing PM, complaint about missing CGI/Util.pm
ERROR 1 and 2
Can’t locate CGI.pm in @INC (you may need to install the CGI module) (@INC contains: /etc/perl /usr/local/lib/aarch64-linux-gnu/perl/5.22.1 /usr/local/share/$
BEGIN failed–compilation aborted at ./notestack-example.cgi line 36.
Grabbed the CGI.pm and Util.pm from my Raspberry Pi by searching for them….

sudo find / -name CGI.pm

sudo find / -name Util.pm

and copying using rcp to/tmp on the board I was setting up, a Pine 64 in this case.

rcp /usr/share/perl/5.14.2/CGI.pm ubuntu@192.168.1.31:/tmp
rcp /usr/share/perl/5.14.2/CGI/Util.pm ubuntu@192.168.1.31:/tmp

The code I was trying to run, the goal of all this work was a script named notestack-example.cgi.
sudo cp /tmp/CGI.pm /etc/perl
./notestack-example.cgi      <— Got ERROR #1
sudo cp /tmp/Util.pm /etc/perl/
./notestack-example.cgi      <— Got ERROR #2
sudo mkdir /etc/perl/CGI
sudo mv /etc/perl/Util.pm /etc/perl/CGI

Final error ERROR 3

Can’t use ‘defined(@array)’ (Maybe you should just omit the defined()?) at /etc/perl/CGI.pm line 528.
Compilation failed in require at ./notestack-example.cgi line 36.
BEGIN failed–compilation aborted at ./notestack-example.cgi line 36.

This one requires removing defined as this is old and not compatible with the current version of Perl.
Just removed the defined on line 528…

ubuntu@pine64:~$ diff /etc/perl/CGI.pm /tmp/CGI.pm
528c528
< if (@QUERY_PARAM && !$initializer) {
—
> if (defined(@QUERY_PARAM) && !defined($initializer)) {

Learned about this trick about removing the ‘defined‘ from…
https://github.com/shenlab-sinai/diffreps/issues/6
https://rt.cpan.org/Public/Bug/Display.html?id=79917