Running perl-script kpcli via cron failed - perl

Question

I'd like to run a script using kpcli (http://kpcli.sourceforge.net/) via cronjob. All works fine when running it interactively.
When running it the following minimum example via cronjob I get the following error-message.
46 22 * * * myuser /usr/local/bin/kpcli --command "vers"
Here the error message
No usable Term::ReadLine::* modules found.
This list was tried:
* Term::ReadLine::Gnu
* Term::ReadLine::Perl
* Term::ReadLine::Perl5
For more information, read the documentation: perldoc kpcli
Here is the output when running it via command line
kpcli: 3.4
Perl: v5.26.1
Operating system: linux ("Ubuntu 18.04.4 LTS")
ReadLine being used: Term::ReadLine::Gnu
Pivotal Perl Modules for kpcli
* File::KeePass: 2.03
* Term::ShellUI: 0.92
* Term::ReadKey: 2.37
* Term::ReadLine: 1.16
* Capture::Tiny: 0.48
* Clipboard: 0.13
* Math::Random::ISAAC: 1.003
* Term::ReadLine::Gnu: 1.35
* Authen::OATH: not installed (optional)
* Sub::Install: not installed (optional)
I also tried to set the variable
PERL5LIB=/usr/lib/x86_64-linux-gnu/perl5/5.26
But nothing changed :(
What's wrong?

Answer 1

I have it :). I have unset all environment variables step by step by shell script. The result was that the variable TERM="xterm" was set in my env but not in the cron env. After setting it in cron all works fine

Answer 2

The PERL5LIB is a user's environment variable; the system's utility cron knows nothing about it.
Further, what you invoke from crontab mostly runs "out of" your home directory; this can depend on the system but it is generally not from where the script is. So then that place is the script's working directory.
Clearly the module Term::ReadLine::Gnu is installed in a non-standard location and when the script runs via cron it altogether cannot find that module (and perhaps yet others).
There are various ways about this
Set PERL5LIB right on the command line in the crontab
SHELL=/bin/bash
MAILTO=your#email.address
* * * * * PERL5LIB=/path/as/needed /full/path/script.pl arguments
The environment variables I set in the beginning are often already set to reasonable values (but they may not be). Consider what other environment may be needed, if any. See your system's documentation for crontab(5) and test
Change to a directory from which the script is known to work
* * * * * (cd /path/to/where/it/works; ./script.pl arguments)
Make the script itself change to the desired working directory by adding to it
use FindBin qw($RealBin);
BEGIN {
chdir $RealBin or die "Can't chdir to $RealBin: $!";
};
This must be done before any use statements that need the script to already be in the particular directory; perhaps all those that refer to non-standard locations.
The solution where the order of compile-time statements matters can be fragile here. On the other hand, in that way the working directory is set up right in the script and sometimes that is precisely what is needed.
There is certainly a rationale for doing both, change the working directory and set PERL5LIB
* * * * * (cd /full/path; PERL5LIB=path1:path2:... ./script.pl arguments)