Double Quotes Inside Double Quotes

youarefunny · 06-06-2010, 07:58 PM

Hello I have a tiny bit of a problem. In bash I need to use some equivalent of double quotes inside double quotes (or the other way around.)

I need to run the following statement to get the output of foo and store it in a variable while passing foo the $file which probably contains spaces.

Code:

variable=$(foo "$file")

The problem is that foo might return an empty string and if it does I need to catch it which will not happen unless I quote the whole thing.

Code:

variable="$(foo "$file")"

but you can't have double quotes inside double quotes for obvious reasons. (no difference between open and close symbols)

I thought that it might not mess up because it would try to find the result of the whole $() first but it doesn't it just tries to do '$(foo '

Is there any way to escape it just for the $() but not send the quotes escaped to foo?

Thanks for any help.

MTK358 · 06-07-2010, 08:15 AM

Code:

variable="$(foo \"$file\")"

Not sure if it will work, but I would try it.

pixellany · 06-07-2010, 09:00 AM

Code:

[mherring@Ath play]$ var='"fred'                                                                                                                              
[mherring@Ath play]$ echo $var                                                                                                                                
"fred                                                                                                                                                         
[mherring@Ath play]$ echo "hello" | sed "/e/$var/"
sed: -e expression #1, char 4: unknown command: `"'                                                                                                           
[mherring@Ath play]$ echo "hello" | sed "s/e/$var/"                                                                                                           
h"fredllo                                                                                                                                                     
[mherring@Ath play]$ echo "hello" | sed "s/e/"fred/"                                                                                                      
> ^C                                                                                                                                                          
[mherring@Ath play]$ echo "hello" | sed "s/e/\"fred/"                                                                                                         
h"fredllo                                                                                                                                                     
[mherring@Ath play]$

So:
SED works as expected when the variable is used (even though the variable is expanded before SED runs the expression??)

The escape is required when trying to use the string containing a quote.

catkin · 06-07-2010, 09:08 AM

The syntax works perfectly -- bash is smarter than you thought:

Code:

c@CW8:~$ foo="$( echo "bar" )"
c@CW8:~$ echo $foo
bar

EDIT: and bash is even smarter than that -- the outermost set of double quotes are not necessary

Code:

c@CW8:~$ foo=$( echo bar none )
c@CW8:~$ echo $foo
bar none

because bash does not perform word-splitting on the expression to the right of an assignment "=".

youarefunny · 06-09-2010, 03:30 PM

Quote:

Originally Posted by MTK358

Code:

variable="$(foo \"$file\")"

Not sure if it will work, but I would try it.

I already tried this. Passes "foo/bar.txt" (with quotes around it) as would be expected.

tuxdev · 06-09-2010, 04:00 PM

Use catkin's answer, it's the right one (a slight nitpick is that the $foo in the echo should be quoted).

catkin · 06-09-2010, 10:21 PM

Quote:

Originally Posted by tuxdev

(a slight nitpick is that the $foo in the echo should be quoted).

Nitpicks are welcome