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I am using bash.
There is an environment variable that I want to either append if it is already set like:
PATH=$PATH":/path/to/bin"
Or if it doesn't already exist I want to simply set it:
PATH="/path/to/bin"
Is there a one line statement to do this?
Obviously the PATH environment variable is pretty much always set but it was easiest to write this question with.
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On Windows 7, just type "system" in the META-Prompt and you'll see an entry "Edit the System Environment Variables". From there, click "Environment variables". There, you can either edit the system variable PATH (bottom list) or add/edit a new PATH variable to the user environment variables.
getenv() method in Python returns the value of the environment variable key if it exists otherwise returns the default value. default (optional) : string denoting the default value in case key does not exists.
Show activity on this post. The || is an “or” comparison operator. The : is a null operator which does… Nothing. Well, it does return a successful exit status…
A little improvement on Michael Burr's answer. This works with set -u (set -o nounset) as well:
PATH=${PATH:+$PATH:}/path/to/bin
PATH=${PATH}${PATH:+:}/path/to/bin
${PATH} evaluates to nothing if PATH is not set/empty, otherwise it evaluates to the current path${PATH:+:} evaluates to nothing if PATH is not set, otherwise it evaluates to ":"
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