Question

I’m writing a shell script that do some work after checking the version of python on the system.

and I do a=`python -V` and a echo of $a:

[root@machine folder]# a=`python -V`
Python 2.3.4
[root@machine folder]# echo $a

and echo $a just output nothing

at the same time I do:

[root@machine folder]# if grep "2.3.4" `python -V` ; then echo "bad" ; fi
Python 2.3.4

after I hit enter it just output the version of the python but nothing else.

Why it behaves like this? Is there other ways for me to do the same task?

Answer 1

python -V appears to output on stderr. If you run

a=`python -V` 

the output appears on the console (i.e. it’s not being picked up by the subshell assignment). However, if you redirect stderr to stdout, then

a=`python -V 2>&1` 

works