Question

In Bash I’m executing a command and putting the result in a variable like this:

export var=`svn ls`

But if SVN fails for some reason–say it returns a non-zero error code–export still returns status code 0. How do I detect if the executed command fails?

Answer 1

var=`svn ls` if [[ $? == 0 ]] then         export var else         unset var fi 

$? is the exit code of the last command executed, which is svn ls here.

jmohr’s solution is short and sweet. Adapted mildly,

var=`svn ls` && export var || unset var 

would be approximately equivalent to the above (export of a valid identifier will never fail, unless you’ve done something horrible and run out of environment space). Take whatever you want — I use unset just to avoid $var possibly having a value even though it’s not exported.