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pythonbash
Joseph Preston
Joseph Preston

Reputation: 23

Comparing python -V output for Python version checking in bash

I am creating an install script where I would like to compare the version of installed default Python with the version I need to have running. Currently here is my code:

#!/bin/bash
PYTHON="$(python -V)"
if [[ "$PYTHON = 'Python 2.7.6' ]]
then echo "Python is installed."
else echo "Python is not installed."
fi

The response I keep getting is that Python is not installed, but that is the output when I type in the command python -V.

Any help is greatly appreciated. Thank you in advance.

Upvotes: 2

Views: 2132

Answers (2)

Jahid
Jahid

Reputation: 22428

You can change your code like this:

#!/bin/bash
PYTHON="$(python -V 2>&1)"
if [[ "$PYTHON" = "Python 2.7.6" ]]; then
    echo "Python is installed."
else
    echo "Python is not installed."
fi

Upvotes: 0

twalberg
twalberg

Reputation: 62369

It seems that when you run python -V, it prints the version to stderr, not to stdout. So, changing your attempt to capture the output into a variable to this:

PYTHON=$(python -V 2>&1)

should do the trick. Another alternative, which tends to include additional information about build dates, compilers, etc. would be:

python -c 'import sys; print sys.version'

or, as suggested by @chepner:

python -c 'import sys; print sys.version_info'

Both of these would require a little additional parsing to get the specific information you want/need, though.

Upvotes: 3

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