Passing Bash Command Through SSH - Executing Variable Capture

Question

I am passing the following command straight through SSH:

ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -i /key/path [email protected] 'bash -s' << EOF
FPM_EXISTS=`ps aux | grep php-fpm`
if [ ! -z "$FPM_EXISTS" ]
then
        echo "" | sudo -S service php5-fpm reload
fi
EOF

I get the following error:

[2015-02-25 22:45:23] local.INFO: bash: line 1: syntax error near unexpected token `('
bash: line 1: ` FPM_EXISTS=root      2378  0.0  0.9 342792 18692 ?        Ss   17:41   0:04 php-fpm: master process (/etc/php5/fpm/php-fpm.conf)

It's like it is trying to execute the output of ps aux | grep php-fpm instead of just capturing git the variable. So, if I change the command to try to capture ls, it acts like it tries to execute that as well, of course returning "command not found" for each directory.

If I just paste the contents of the Bash script into a file and run it it works fine; however, I can't seem to figure out how to pass it through SSH.

Any ideas?

Community · Accepted Answer · 2017-05-23 12:32:39Z

9

You need to wrap starting EOF in single quotes. Otherwise ps aux | grep php-fpm would get interpreted by the local shell.

The command should look like this:

ssh ... [email protected] 'bash -s' << 'EOF'
FPM_EXISTS=$(ps aux | grep php-fpm)
if [ ! -z "$FPM_EXISTS" ]
then
        echo "" | sudo -S service php5-fpm reload
fi
EOF

Check this: http://tldp.org/LDP/abs/html/here-docs.html (Section 19.7)

Btw, I would encourage you to use $() instead of backticks consequently for command substitution because of the ability to nest them. You will have more fun, believe me. Check this for example: What is the benefit of using $() instead of backticks in shell scripts?

edited May 23, 2017 at 12:32

CommunityBot

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answered Feb 25, 2015 at 23:05

hek2mgl

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Comments

Tim Groeneveld · Accepted Answer · 2015-02-25 23:07:19Z

5

You should wrap the EOF in single quotes.

ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -i /key/path [email protected] 'bash -s' << 'EOF'
FPM_EXISTS=`ps aux | grep php-fpm`
if [ ! -z "$FPM_EXISTS" ]
then
        echo "" | sudo -S service php5-fpm reload
fi
EOF

answered Feb 25, 2015 at 23:07

Tim Groeneveld

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4 Comments

hek2mgl Over a year ago

Wondering what makes out the difference compared to my answer? (Except the missing explanation)

thasmo Over a year ago

The time of posting. (Eh, nevermind - but it was nearly the same time. ;)

Tim Groeneveld Over a year ago

@hek2mgl, sorry my friend. At the time I started writing & testing my answer, I didn't see that you had already written something.

hek2mgl Over a year ago

also it is not a "race". however, I really saw guys copying posts... sorry for blaming you! +1 nice answer ;)

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