Command substitution: cat with executable content

Question

I have a file called test and the contents are:

ubuntu@regina:~$ cat test
** test **

catting this file via command line works fine, but if I use command substitution I get an understandable but undesirable result.

ubuntu@regina:~$ A=$(cat test)
ubuntu@regina:~$ echo $A
deployment detect.sh htpasswd.py logs test uwsgi-1.0.4 uwsgi-1.0.4.tar.gz test deployment        detect.sh htpasswd.py logs test uwsgi-1.0.4 uwsgi-1.0.4.tar.gz

Because of the asterisks that exist in the file test it basically executes an echo * and lists the directory contents along with the file contents.

Is there a parameter I can pass to the command substitution syntax that will not provide this result, or is there another idiom that should be used for this?

Solution

You want to do echo "$A". Wrapping the variable in the quotes makes it a string.

Example:

[root@talara test]# A=$(<test)
[root@talara test]# echo $A
FILE1 ham test test FILE1 ham test
[root@talara test]# echo "$A"
** test **

Comments

[Tim]

Note: using cat to read a single file is less efficient then reading the file, example: A=$(cat test) VS. A=$(<test)

[glenbot]

Thank you, I didn't know that about that idiom

[glenbot]

Thanks tim! That's exactly what I was looking for. Funny, I knew about quotes and now that I see the answer I feel pwned.

[Tim]

no prob. Shell quotes are like that, I forget often as well!