Checking if pip is install via script

Question

So this may have been a dumb way of doing it but I wanted to check if pip was installed via a script, so I ran the pip version command and checked if the first 3 characters of the command were "pip" and if so I could say I knew pip was installed. Problem is when I run this and get a command not found error, the logic still thinks pip is installed. Why is? What is that command not found error returning? It can't be pip right so why does pip not install? And what's a better way of detecting if pip is installed?

pip=$(sudo /root/.local/bin/pip -V | cut -c 1-3)
if [[ pip != "pip" ]]; then
    echo "Installing pip..."
    curl https://bootstrap.pypa.io/get-pip.py -o /tmp/get-pip.py
    sudo /workplace/user/package/src/EnvImprovement/bin/python2.7 get-pip.py --user
else
    echo "Pip detected."
fi

In this line [[pip != "pip"]], may I know why there is a list inside another list? Is it causing an issue? — Rajesh Kumar, Oct 04 '18 at 20:31
@RajeshKumar This is syntax that I was seeing when I was looking up shell script conditionals. I can edit it and see if this causes a problem though. I don't believe it is though. — Joseph hooper, Oct 04 '18 at 20:35

score 1 · Accepted Answer · answered Oct 04 '18 at 20:44

You're testing whether the string pip is equal to the string pip, which it is. The pip variable isn't involved.

Unlike in Python, pip and "pip" are equivalent in a shell script. The quotes in "pip" suppress special interpretation of a number of characters, none of which are actually present in pip anyway. You need $pip to perform variable expansion.

Even then, hardcoding /root/.local/bin/pip doesn't make much sense, and executing pip by a hardcoded path to determine whether it exists seems like a strange idea compared to testing whether an executable exists at that path, or taking a different approach altogether.

You should probably use command -v pip instead of your current approach.

Wow I left off the $ I can't believe it. Thanks. – Joseph hooper Oct 04 '18 at 20:52 — Joseph hooper, Oct 04 '18 at 20:52

Checking if pip is install via script

1 Answers1