Perl inline replace in shell script not working as expected

Question

I have a perl inline replace command in a shell script that isn't working for some reason. With below command, its replacing all ":" with replacement string in the perl command.

When I manually ssh to the box and running the perl command works as expected.

ssh host "cd /x/somedirectory && perl -pi -e 's#\${somehost}:\${someport}#10.20.30.40:8443#g' config/app.properties"

Edit1

Please note that $somehost and $someport are NOT shell variables. I'm looking for a literal text replacement.

What am I doing wrong? I tried using different delimiters, escaping { and } etc but still no luck.

@HunterMcMillen I see what you are saying now. $somehost and $someport are not shell variables. I'm looking for a literal text replacement. I'm editing the question — nilesh
– nilesh, Commented Nov 13, 2015 at 16:32
Figuring out escapes in a one-liner inside a shell script is like trying to train ants to juggle. Just do the whole thing in Perl using Net::SSH. Or failing that, put the code from the one-liner inside a file, and run it like ssh host "perl -pi code.pl /x/somedir/config/app.properties — TLP
– TLP, Commented Nov 13, 2015 at 18:56

ikegami · Accepted Answer · 2015-11-13 19:36:57Z

3

To create a single-quoted shell literal from a string, escape ' by replacing them with '\''.

To create a double-quoted shell literal from a string, escape \, " and $ by prefixing them with \.

The Perl command you want is

s#\${somehost}:\${someport}#10.20.30.40:8443#g

So the remote shell command you want is

perl -pi -e 's#\${somehost}:\${someport}#10.20.30.40:8443#g' config/app.properties

So the local shell command you want is

ssh host 'perl -pi -e '\''s#\${somehost}:\${someport}#10.20.30.40:8443#g'\'' config/app.properties'

or

ssh host "perl -pi -e 's#\\\${somehost}:\\\${someport}#10.20.30.40:8443#g' config/app.properties"

[Removed cd /x/somedirectory && to keep things simple. Just add it back in.]

edited Nov 13, 2015 at 19:36

answered Nov 13, 2015 at 17:29

ikegami

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5 Comments

ikegami Over a year ago

Both versions I posted work. Aside from doing this every day, I have tested them. Did you miscopy something (e.g. used " instead of ')? Or maybe you're not using bash (on both machines) as tagged?

nilesh Over a year ago

I tried this

ssh host "perl -pi -e '\''s#\${somehost}:\${someport}#10.20.30.40:8443#g'\'' /x/web/STAGE2MS034/paymentapiplatformserv/config/app.properties"

. I get bash: -c: line 0: unexpected EOF while looking for matching ''`

ikegami Over a year ago

That's doesn't match either of my solutions. You used ", so you need to use the escape mechanism for ", but you used the escape mechanism for '. Either use the appropriate escape mechanism (second solution), or use ' instead of " (first solution).

nilesh Over a year ago

Ahh..thanks that works. One day I'll get better at bash

ikegami Over a year ago

Just add each layer of escaping one at a time as i showed. // 'abc'\''def' is 'abc' (abc), \' ('), and 'def' (def) one after the other, resulting in abc'def.

mob · Accepted Answer · 2015-11-13 17:23:05Z

2

The shell on the remote machine will perform another level of escaping. To receive the sequence \$ on the remote machine you have to send the sequence \\\$:

ssh host "cd /x/somedirectory && perl -pi -e 
    's#\\\${somehost}:\\\${someport}#10.20.30.40:8443#g' config/app.properties"

answered Nov 13, 2015 at 17:23

mob

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1 Comment

ikegami Over a year ago

Note: Only works if you remove the line break or if you add \\ before the line break.

salva · Accepted Answer · 2015-11-13 19:09:23Z

2

So, you can write Perl...

#!/usr/bin/perl

use Net::OpenSSH;
my $ssh = Net::OpenSSH->new($host);
my $old = quotemeta("${somehost}:${someport}");
$ssh->system('cd', $some_directory, \\'&&',
             'perl', '-pi', '-e',
             "s|$old|10.20.30.40:8443|g",
             'config/app.properties');

answered Nov 13, 2015 at 19:09

salva

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Comments

anubhava · Accepted Answer · 2015-11-13 17:30:17Z

0

Try this ssh command with here-doc and avoid all escaping:

ssh -t -t host<<'EOF'
cd /x/somedirectory &&
    perl -i -pe 's#\${somehost}:\${someport}#10.20.30.40:8443#g' config/app.properties
exit
EOF

edited Nov 13, 2015 at 17:30

answered Nov 13, 2015 at 16:21

anubhava

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8 Comments

nilesh Over a year ago

still no luck. You forgot { and } in your answer. I added them but I get same result

ThisSuitIsBlackNot Over a year ago

@nilesh Are you trying to replace the literal text ${somehost}, or the value of the bash variable $somehost?

nilesh Over a year ago

@ThisSuitIsBlackNot you got it. I'm trying to replace literal text. $somehost and $someport are not shell variables

nilesh Over a year ago

@anubhava sorry for the confusion, $somehost and $someport are not shell variables. I'm looking for a literal text replacement

ThisSuitIsBlackNot Over a year ago

perl -pei 'foo' is equivalent to perl -pe 'i' foo (i.e. run the code i on file foo), you need perl -i -pe 'foo'. Also, you have to escape the $ in the regex so it doesn't mean end-of-line: perl -i -pe 's#\${somehost}:\${someport}#10.20.30.40:8443#g'

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