I notice that in Lib.pm, the function 'cmdSystemOrEvalLong'
specifically uses the structure 'exec {$cmd->[0]} @$cmd;' so that no
shell is invoked.
I know that technically it's a little faster to avoid calling the
shell, but in many cases it is very useful to have at least a
rudimentary shell available.
For example, I may want to read in (rather than execute a script).
Specifically say,
(1) $Conf{DumpPreUserCmd} = qq(\$sshPath -q -x -i $BackupPCsshID -l
$Conf{RsyncdUserName} \$hostIP bash -s < /etc/backuppc/scripts/script-\$hostIP)
would allow me to run a hostIP specific script that I store in
/etc/backuppc/scripts.
- This is neater and easier to maintain than having to store the script
on the remote machine.
- This also seems neater and nicer than having to use an executable
script that would itself need to run ssh -- plus importantly it
removes a layer of indirection and messing with extra quoting.
Similarly, it would be great to be able to support:
(2) $Conf{DumpPreUserCmd} = qq(\$sshPath -q -x -i $BackupPCsshID -l
$Conf{RsyncdUserName} \$hostIP bash -s <<EOF
<bash script here>
EOF)
Or similarly:
(3) $Conf{DumpPreUserCmd} = qq(\$sshPath -q -x -i $BackupPCsshID -l
$Conf{RsyncdUserName} \$hostIP bash -s <<< $bashscript
where for example
my $bashscript = <<'EOF'
<bash script here>
EOF
Though this latter form is a bash-ism and would not work in /bin/sh
The advantage of the latter examples is that it would allow me to
store the bashscript in the actual host.pl config scripts rather than
having to have a separate set of scripts to load.
Note that I am able to roughly replicate (3) using perl code, but it
requires extra layers of escaping of metacharacters making it hard to
write, read, and debug.
For example something like:
my $bashscript = <<'EOF';
<bash script here>
EOF
$bashscript =~ s/([][;&()<>{}|^\n\r\t *\$\\'"`?])/\\$1/g;
$Conf{DumpPreUserCmd} = qq(&{sub {
open(my \$out_fh, "|-", "\$sshPath -q -x -i $BackupPCsshID -l
$Conf{RsyncdUserName} \$hostIP bash -s")
or warn "Can't start ssh: \$!";
print \$out_fh qq($bashscript);
close \$out_fh or warn "Error flushing/closing pipe to ssh: \$!";
}})
Though it doesn't quite work yet...
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