bash - Function to escape character?

Question

I am trying to automate some of my stuff and facing a issue, the problem boils down to escaping the value that is being passed as a argument to the script.

myScript.sh

#!/bin/bash

loadPatch -name $1

where $1 is the first argument and can have value like 'p12.9.5-bug34'

Running it as

myScript p12.9.5-bug34

produces no result. I checked with echo $? the output was successful, but the required operation didn't happen.

I replaced $1 with this actual value to test in the script and it worked as expected. There is no way for me to put a print statement in loadPatch to verify what arguments it has received.

So, I envisage there is some escaping problem here and hence need to know, is there any function/utility which I could use to escape the argument before using?

Please let me know if you see any other error with this?

Answer 1

To answer the question asked, because others may search for this title:

• zsh only: print -r -- ${(q)var} ${(qq)var} ${(qqq)var} ${(qqqq)var} for different types of quoting.
• ksh93, zsh, or bash: printf %q "$var"

• BusyBox (and all above).

  Use of vars level out differences between ash, bash and ksh:

  q1="'"
  q2="'\''"
  printf '%s\n' "'${var//$q1/$q2}'"
  

  Not in dash and old shells (those missing ${var//pat/str}).

• most portable?

  printf "'%s'\n" "$(printf '%s' "$var" | sed "s/'/'\\\\''/g")"
  
  Or
  
  printf '%s\n' "$var" | sed "s/'/'\\\\''/g; 1s/^/'/; \$s/$/'/"
  

Improvements gladly welcomed!

Answer 2

I agree there should not be a problem with special characters in that filename.

I have found that sometimes scripts are not running in the folder I expected. If you replace "loadPatch -name" with "echo" you can verify $1 is what you expect. If it is what you expect then add these lines to see if the current directory is what you expect:

ls -l $1
pwd