Use of uninitialized value $a in concatenation (.) or string - regex

Question

I am trying to remove the old files in a dir if the count is more than 3 over SSH
Kindly suggest how to resolve the issue.
Please refer the code snippet
#!/usr/bin/perl
use strict;
use warnings;
my $HOME="/opt/app/latest";
my $LIBS="${HOME}/libs";
my $LIBS_BACKUP_DIR="${HOME}/libs_backups";
my $a;
my $b;
my $c;
my $d;
my $command =qq(sudo /bin/su - jenkins -c "ssh username\#server 'my $a=ls ${LIBS_BACKUP_DIR} | wc -l;my $b=`$a`;if ($b > 3); { print " Found More than 3 back up files , removing older files..";my $c=ls -tr ${LIBS_BACKUP_DIR} | head -1;my $d=`$c`;print "Old file name $d";}else { print "No of back up files are less then 3 .";} '");
print "$command\n";
system($command);
output:
sudo /bin/su - jenkins -c "ssh username#server 'my ; =ls /opt/app/latest/libs_backups | wc -l;my ; =``;if ( > 3); { print " Found More than 3 back up files , removing older files..";my ; =ls -tr /opt/app/latest/libs_backups | head -1;my ; =``;print "Old file name ";}else { print "No of back up files are less then 3 .";} '"
Found: -c: line 0: unexpected EOF while looking for matching `''
Found: -c: line 1: syntax error: unexpected end of file

Answer 1

If you have three levels of escaping, you're bound to get it wrong if you do it manually. Use String::ShellQuote's shell_quote instead.
Furthermore, avoid generating code. You're bound to get it wrong! Pass the necessary information using arguments, the environment or some other channel of communication instead.
There were numerous errors in the interior Perl script on top of the fact that you tried to execute a Perl script without actually invoking perl!
#!/usr/bin/perl
use strict;
use warnings;
use String::ShellQuote qw( shell_quote );
my $HOME = "/opt/app/latest";
my $LIBS = "$HOME/libs";
my $LIBS_BACKUP_DIR = "$HOME/libs_backups";
my $perl_script = <<'__EOI__';
use strict;
use warnings;
use String::ShellQuote qw( shell_quote );
my ($LIBS_BACKUP_DIR) = #ARGV;
my $cmd = shell_quote("ls", "-tr", "--", $LIBS_BACKUP_DIR);
chomp( my #files = `$cmd` );
if (#files > 3) {
print "Found more than 3 back up files. Removing older files...\n";
print "$_\n" for #files;
} else {
print "Found three or fewer backup files.\n";
}
__EOI__
my $remote_cmd = shell_quote("perl", "-e", $perl_script, "--", $LIBS_BACKUP_DIR);
my $ssh_cmd = shell_quote("ssh", 'username#server', "--", $remote_cmd);
my $local_cmd = shell_quote("sudo", "su", "-c", $ssh_ccmd);
system($local_cmd);

Answer 2

I created a new file and handling the dir check and deletion logic , scp file to remote server and executing in remote server , after completion removing the file.
#!/usr/bin/perl
use strict;
use warnings;
use File::Basename;
use File::Path;
use FindBin;
use File::Copy;
my $HOME="/opt/app/test/latest";
my $LIBS_BACKUP_DIR="${HOME}/libs_backups";
my $a="ls ${LIBS_BACKUP_DIR} | wc -l";
my $b=`$a`;
my $c="ls -tr ${LIBS_BACKUP_DIR} | head -1";
my $d=`$c`;
chomp($d);
print " count : $b\n";
if ($b > 3)
{
print " Found More than 3 back up files , removing older files..\n";
print "Old file name $d\n";
my $filepath="${LIBS_BACKUP_DIR}/$d";
rmtree $filepath;
}
else
{
print "No of back up files are less then 3 .\n";
}