A "clean" way to parse a variable containing whitespaces and quotes to cp or mv

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#1

Hello,

I was wondering if there is any “clean” way to parse a variable containing whitespaces and quotes to cp or mv in bash.
Let’s say, we have a directory “test test” and want to move it into a directory “test2” from the same folder. But the “test test” is saved in a variable $fname.
If I now try something like


#!/bin/bash
fname="test test"
mv \'$fname\' test2/

or


#!/bin/bash
fname="'test test'"
mv "$fname" test2/

(echo $fname will give ‘test test’ here as output)
I get an error message such as

cp: cannot stat ‘'test test.D'’: No such file or directory

However, if I echo these commands instead of running them and then copy the results, paste them direct into terminal and run, they work.

#!/bin/bash
fname='test test'
fname2="'test test'"
echo $fname
echo $fname2
echo "cp -R '$fname' test2"
echo "cp -R $fname2 test2"

Both echos result in


cp -R 'test test' test2

Running which leads to the desired result.
My “dirty” solution to the whole problem is then


#!/bin/bash
echo "#!/bin/bash">runtest2.sh
chmod 755 runtest2.sh
fname='test test.D'
echo "cp -R '$fname' test2">>runtest2.sh
#echo the command into a new script
#there it will appear as "cp -R 'test test' test2"
./runtest2.sh

Which works (of course, the real problem does not contain one file with a known name but multiple file names stored in a file); but I wonder whether there is a “cleaner” solution for this not including creating and executing of a second script.
Does anyone have an idea?

#2 

touch 'test test'
var='test test'
ll 'test test'
mv "${var}" something-else

Hope that helps. Basically, use double-quotes so that you can get your
variable interpolation without string-concatenating single-quotes to the
whole thing which is messing you up. You may not need the braces around
the variable name, but it’s good practice regardless.

–
Good luck.

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#3

That works indeed. Thanks, good to learn that. I have basically tried to use to many quotes …:slight_smile:

#4

now that you have something ‘working’ let me pls add a more general answer.

A good read is http://mywiki.wooledge.org/BashPitfalls.
And also very important may be the size of the list you have to work on, so pls read about xargs.

I always use a while loop and read to get file names. If you use any search engine, you’ll find a lot about while loops in bash dealing with file names. Here is 1 example about globbing, special characters (like 2 dashes at beginning of file names) and read command in a while loop to process a list of file names:
http://unix.stackexchange.com/questions/9496/looping-through-files-with-spaces-in-the-names

HTH
Shvenky, posting from Shvenk’s Lair

#5

Thank you for additional info. I was already using while and read in the full version of my “dirty” solution at the moment I posted the thread, but I was just curious why I could not use cp or mv directly.

Konstl