Shell Programming and Scripting

sed -r 's/(^[^"]*)"/\1^A/; s/"([^"]*$)/^A\1/; s/"//g; s/^A/"/g' file

"Hey, I was ready to go on stage or "break a leg", but I failed miserably."
"Of course, never say never. This is perhaps a "See you later"rather than a "Goodbye". Thank you for reading."
"I\'ve been rehabilitated. It\'s such a "wonderful" account of her journey."
"This is a test"
Here are some more test
Now we have a single ", just for test

awk '/^"/ {gsub(/^"|"$/,"§");gsub(/"/,"");gsub(/§/,"\"")}1' file

"Hey, I was ready to go on stage or break a leg, but I failed miserably."
"Of course, never say never. This is perhaps a See you laterrather than a Goodbye. Thank you for reading."
"I\'ve been rehabilitated. It\'s such a wonderful account of her journey."
"This is a test"
Here are some more test
Now we have a single ", just for test

Last login: Sat Aug 31 19:20:17 on ttys000
AMIGA:barrywalker~> text="\"This is a \"quote within\" a quote.\""
AMIGA:barrywalker~> echo -e -n "$text" > /tmp/quotes.txt
AMIGA:barrywalker~> text=""
AMIGA:barrywalker~> newtext=""
AMIGA:barrywalker~> read text < /tmp/quotes.txt
AMIGA:barrywalker~> echo "$text"
"This is a "quote within" a quote."
AMIGA:barrywalker~> echo "${#text}"
35
AMIGA:barrywalker~> # Correct string length...
AMIGA:barrywalker~> for n in $( seq 0 1 ${#text} ); do if [ "${text:$n:1}" == '"' ]; then newtext=$newtext; else newtext=$newtext${text:$n:1}; fi; done
AMIGA:barrywalker~> echo "$newtext"
This is a quote within a quote.
AMIGA:barrywalker~> echo "${#newtext}"
31
AMIGA:barrywalker~> # Correct string length...
AMIGA:barrywalker~> # Done longhand and will be slow but works.
AMIGA:barrywalker~>
AMIGA:barrywalker~> text="\"This is a \"quote within\" a quote.\""
AMIGA:barrywalker~> newtext=""
AMIGA:barrywalker~> for n in $( seq 0 1 ${#text} ); do if [ "${text:$n:1}" == '"' ]; then newtext=$newtext"'"; else newtext=$newtext${text:$n:1}; fi; done
AMIGA:barrywalker~> echo "$newtext"
'This is a 'quote within' a quote.'
AMIGA:barrywalker~> # Quotes changed from double to single...
AMIGA:barrywalker~> _

${text:$n:1}