Stripping single and double quotes in a string using bash / standard Linux commands only

I’m looking for something that will translate a string as follows, using only bash / standard Linux commands:

1. Single-quotes surrounding a string should be removed
2. Double-quotes surrounding a string should be removed
3. Unquoted strings should remain the same
4. Strings with unmatched surrounding quotes should remain the same
5. Single-quotes that don’t surround the string should remain
6. Double-quotes that don’t surround the string should remain

For example:

• ‘Food’ should become Food
• “Food” should become Food
• Food should remain the same
• ‘Food” should remain the same
• “Food’ should remain the same
• ‘Fo’od’ should become Fo’od
• “Fo’od” should become Fo’od
• Fo’od should remain the same
• ‘Fo”od’ should become Fo”od
• “Fo”od” should become Fo”od
• Fo”od should remain the same

Thank you!

Answer

This should do it:

sed "s/^(["'])(.*)1$/2/g" in.txt

Where in.txt is:

"Fo'od'
'Food'
"Food"
"Fo"od'
Food
'Food"
"Food'
'Fo'od'
"Fo'od"
Fo'od
'Fo"od'
"Fo"od"
Fo"od

And expected.txt is:

"Fo'od'
Food
Food
"Fo"od'
Food
'Food"
"Food'
Fo'od
Fo'od
Fo'od
Fo"od
Fo"od
Fo"od

You can check they match with:

diff -s <(sed "s/^(["'])(.*)1$/2/g" in.txt) expected.txt