I'm really new to shell script and I would like to check for software version number and set condition upon it.
ex: check if python version > 2.7.0 then ...
I can check for python using this:
if [ "$(python -V 2>&1)" ]
then
pyv="$(python -V 2>&1)"
echo "$pyv"
fi
Python's output is not immediately useful:
$ python -V
Python 2.7.9
The output includes a word, Python, and a version number. Further, because the version number has two decimal points, it is not a valid number.
One approach is to convert the version into a valid decimal number:
$ python -V 2>&1 | awk -F'[ .]' '{printf "%s.%s%02.f",$2,$3,$4}'
2.709
In this form, version 2.7.10 would become 2.710. This approach works up through point version of 99. If you think there is a chance that python will release a point version 100, then we would want to change the format slightly.
We can now compare number using bc:
$ echo "$(python -V 2>&1 | awk -F'[ .]' '{printf "%s.%s%02.f",$2,$3,$4}') > 2.7" | bc -l
1
$ echo "$(python -V 2>&1 | awk -F'[ .]' '{printf "%s.%s%02.f",$2,$3,$4}') > 2.710" | bc -l
0
To use that in an if statement:
if echo "$(python -V 2>&1 | awk -F'[ .]' '{printf "%s.%s%02.f",$2,$3,$4}') > 2.7" | bc -l | grep -q 1
then
echo version greater than 2.7
fi
If the test is successful, bc -l prints a 1 to standard out. To silently test for the presence of 1, we use grep -q 1.
We use awk to convert the version number to an integer form:
$ python -V 2>&1 | awk -F'[ .]' '{printf "%2.f%02.f%02.f",$2,$3,$4}'
20709
Now, we can use standard shell tools to test the version:
if [ "$(python -V 2>&1 | awk -F'[ .]' '{printf "%2.f%02.f%02.f",$2,$3,$4}')" -gt 20700 ]
then
echo version greater than 2.7
fi
sort -VGNU sort has a version sorting feature. To use it, we create input useful for version sorting:
$ t="Python 2.7.0"
$ echo "$(python -V 2>&1)"$'\n'"$t" | sort -V -k2,2
Python 2.7.0
Python 2.7.9
Now, we sort in ascending order:
$ echo "$(python -V 2>&1)"$'\n'"$t" | sort -V -k2,2
Python 2.7.0
Python 2.7.9
If the first line is $t, that means that the actual python version is newer:
t="Python 2.7.0"
if echo "$(python -V 2>&1)"$'\n'"$t" | sort -V -k2,2 | head -n1 | grep -q "$t"
then
echo "version greater than $t"
fi
Since GNU sort -V is designed to handle version numbers natively, this is the approach that I prefer.
