Using Arguments in a Shell Scriptby dave on 2009-05-11
Within 5 seconds of looking at a shell script I'm usually opening a new file in my text editor to re-write the ugliness into something that makes more visual sense. To me at least python is highly preferable.
Still I use shell scripts all the time to batch a group of commonly used sequential executions, or to abbreviate a commonly used but lengthy commands.
Today I looked into going one step further into the complexities of shell scripts, probably my last step for a while, and discovered how to handle arguments.
The inspiring work case was in using Django manager to run tests for the different apps
./manage.py test --settings test_settings <optional app names>
The following script will check if an argument exists and if it does it will use the argument in the tests command.
if [ -n "$1" ] # Test whether command-line argument is present (non-empty). then ./manage.py test --settings test_settings $1 else ./manage.py test --settings test_settings fi
Notice that $1 refers to the first argument ($0 refers to the name of the executable and $5 refers to the 5th argument).
Save the file as 'test' and then modify it as an executable
chmod +x test
And now I can run the tests on their own
or with an argument app
Note that the above example has a limitation of only dealing with the first argument and seems a bit redundant. The entire script can indeed be shortened to
./manage.py test --settings test_settings $@
As $@ represents all arguments after $0.