remote shell call with awk from perl script

Question

I'm trying to execute commands on a remote host from a perl script.

$check = `rsh host1 "df -k /backup/|tail -1|awk \'{print \$5}\'"`;
print $check

But awk returns me the whole string instead of one column.

/dev/md/dsk/d10      4133838 1936684 2155816    48%    /

I need only

48%

Looks like there is an issue in escaping but don't know what exactly wrong. Please help.

is this working? Where is your ending double quotes? Wht are you escaping quotes and $? — SMA, Dec 29 '14 at 09:32
I'm unsure, but try removing the quotes around the command. i.e: `$check = \`rsh host1 df -k /backup/|tail -1|awk '{print \$5}'\`;` should do — Tensibai, Dec 29 '14 at 09:45
That is not Perl code. Perl uses `print`, not `echo`. It might be php. — TLP, Dec 29 '14 at 11:09

score 3 · Accepted Answer · answered Dec 29 '14 at 09:54

One option would be to use qx with the single quote as a delimiter instead, so that Perl variables are not interpolated:

$check = qx'rsh host1 "df -k /backup/|tail -1|awk \"{print \$5}\""';

I have used double quotes around the awk command, so it is still necessary to escape the $5 to prevent it from being interpreted as a shell variable.

If you are happy to run tail and awk on the local machine, you can remove the double quotes:

$check = qx'rsh host1 df -k /backup/|tail -1|awk "{print \$5}"';

This results in more data being copied back from the remote machine, which may or may not be a problem.

Alternatively, you could split the output using Perl and avoid the problem entirely:

$check = (split /\s+/, qx'rsh host1 "df -k /backup/|tail -1"')[4];

What an awesome answer! Thank you for your tips. – user947668 Dec 29 '14 at 10:28 — user947668, Dec 29 '14 at 10:28

remote shell call with awk from perl script

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