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I have a situation here, I am trying to run a sed command on a remote shell inside my shell script and using variables that are dynamic and end up getting the same error again and again.

This is the sed command that is running fine on local shell without any error. I have used this regular expression after thorough testing and trust me there is no problem with it.

sed -i 's/  #0\t30718/ 0\t30718/' ./config.txt

Trying to run this in a remote shell using ssh:

ssh root@sys_name sed -i 's/  #0\t30718/ 0\t30718/' /absolute-path/vconfig.txt

And when I try to run this command using variables. (30718 and path of the file are the variables):

ssh root@sys_name 'sed -i "s/0\t${pe_list[0]}/#0\t${pe_list[0]}/g" $file_path'

or like this:

ssh root@sys_name "sed -i 's/0\t${pe_list[0]}/#0\t${pe_list[0]}/g' $file_path"

I either get the sed: -e expression #1, char 2: unterminated `s' command error or the sed command executes with undesired output matching the variable names as is. Basically, put in few words, I want to execute a sed command on a remote shell using ssh, and the constraint is that the entire command is part of a script and the values to be matched and the filename are variables in that file.

control-zed
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  • I assume `${pe_list[0]}` and/or `${pe_list[0]}` contains one or more slashes (`/`). See: [Escaping forward slashes in sed command](https://stackoverflow.com/q/40714970/3776858) – Cyrus Oct 30 '18 at 05:58
  • No. They are just numbers. Like p=(30718 30719 30720). – control-zed Oct 30 '18 at 09:20

1 Answers1

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You have variable set in your local shell, but is is not sed variable, so you should exit sed environment by closing it with single quote, put your variable, then open again with single quote and continue sed stuff:

sed -e 's/Red Hat/'${z}'/' /etc/redhat-release

In case your $z variable contains spaces, you need to embrace it with double quotes:

sed -e 's/Red Hat/'"${z}"'/' /etc/redhat-release

Finally, when you sending your command through ssh you are also adding double quotes around whole command, so all double quotes used in this command should be escaped, else everything between these will be evaluated locally on your source host. So do like this:

z="BLACK HAT"    
ssh root@sys_name "sed -e 's/Red Hat/'\"${z}\"'/' /etc/redhat-release"

You will get:

BLACK HAT Enterprise Linux Server release 6.10 (Santiago)
Petras L
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  • This was just the problem with the quotes. It is really confusing. Thanks for your answer it was really helpful. Any references about this would be much appreciated. @Petras L – control-zed Oct 30 '18 at 09:18