How to escape the single quote character in an ssh / remote bash command?

Question

I\'m building a small set of scripts for remotely starting, stopping and checking the status of a process. The stop of these scripts should look for a process a

Answer 1

This is not ssh or awk handling the quotes, it is the shell (and they are necessary to keep the shell from handling other characters specially, like $). Nesting them is not supported (although other structures, such as $() may nest even while containing quotes), so you'll need to escape the single quotes separately. Here are a couple of methods:

$ echo 'Don'"'"'t mess with this apostrophe!'
Don't mess with this apostrophe!
$ echo 'Don'\''t mess with this apostrophe!'
Don't mess with this apostrophe!

Answer 2

Use

ssh deploy@hera 'kill -9 `ps -ef | grep MapReduceNode | grep -v "grep" | awk -F " " '"'"'{print $2}'"'"' | head -n 1`'

Explanation:

ssh deploy@hera 'kill -9 `ps -ef | grep MapReduceNode | grep -v "grep" | awk -F " " '"'"'{print $2}'"'"' | head -n 1`'
                >                               1                                   <>2<>    3     <>4<>      5      <

1) First string with beginning of command: 'kill -9 `ps -ef | grep MapReduceNode | grep -v "grep" | awk -F " " '

2) Second string with only a single ' char: "'"

3) Third string with the print command: '{print $2}'

4) Fourth string with another single quote: "'"

5) Fifth string with rest of command: ' | head -n 1`'

Answer 3

You can't include a single quote in a single-quoted string. However, that doesn't matter because a single argument can have more than one quoted segment (as long as there is no unquoted whitespace or other self-delimiting characters.)

For example:

ssh deploy@hera 'kill -9 `ps -ef |
                 grep MapReduceNode |
                 grep -v "grep" |
                 awk -F " " '\''{print $2}'\'" |
                 head -n 1`"

However, that command line is very clunky. If possible, you should use the pkill utility, which would reduce all that to ssh deploy@hera 'pkill -SIGKILL MapReduceNode'.

Otherwise you could do all the string manipulation in a single awk invocation (untested, but I think it will work):

ssh deploy@hera 'ps -ef |
                 awk "/[M]apReduceNode/{system(\"kill -9 \"$2)}"'

(unlike the original, this will kill all MapReduceNode tasks rather than some arbitrary first one. If you really want to just do in one task, add ; exit to the awk action.)

Answer 4

Another example is to deal with simple or double quotes because for me for example I needed interpretation and variable replacements. If I want to make a function to display a msg to the macOS of my woman I can do followings:

ssh womanLptp "osascript -e 'tell app \"System Events\" to display dialog \"${1}\"'"

Answer 5

There are two more options I don't see mentioned in any of the other answers. I've left the grep/grep/awk/head pipeline intact for demonstration purposes, even though (as alluded to in rici's answer) it could be reduced to something like

awk -F ' ' '/MapReduceNod[e]/ {print $2; exit}'

1. Using double quotes for the whole ssh command:

   ssh deploy@hera "kill -9 \$(ps -ef |
   grep MapReduceNode | grep -v \"grep\" | awk -F ' ' '{print \$2}' | head -n 1)"
   

   Notice that I can use single quotes in the command now, but I have to escape other things I don't want expanded yet: \$() (which I've used instead of backticks), double quotes \", and print \$2.

2. A here-doc with quoted delimiter:

   ssh -T deploy@hera <<'EOF'
   kill -9 $(ps -ef | grep MapReduceNode | grep -v 'grep' |
   awk -F ' ' '{print $2}' | head -n 1)
   EOF
   

   The -T prevents ssh from complaining about not allocating a pseudo-terminal.

   The here-doc with quoted delimiter is extra nice because its contents don't have to be modified at all with respect to escaping things, and it can contain single quotes.