Bash: Detect if user's path has a specific directory in it

Question

With /bin/bash, how would I detect if a user has a specific directory in their $PATH variable?

For example

if [ -p "$HOME/bin" ]; then
  echo "Your path is missing ~/bin, you might want to add it."
else
  echo "Your path is correctly set"
fi

Answer 1

echo "$PATH" | grep -q "\(^\|:\)$HOME/bin\(:\|\$\)"

Answer 2

Something really simple and naive:

echo "$PATH"|grep -q whatever && echo "found it"

Where whatever is what you are searching for. Instead of && you can put $? into a variable or use a proper if statement.

Limitations include:

• The above will match substrings of larger paths (try matching on "bin" and it will probably find it, despite the fact that "bin" isn't in your path, /bin and /usr/bin are)
• The above won't automatically expand shortcuts like ~

Or using a perl one-liner:

perl -e 'exit(!(grep(m{^/usr/bin$},split(":", $ENV{PATH}))) > 0)' && echo "found it"

That still has the limitation that it won't do any shell expansions, but it doesn't fail if a substring matches. (The above matches "/usr/bin", in case that wasn't clear).

Answer 3

Using grep is overkill, and can cause trouble if you're searching for anything that happens to include RE metacharacters. This problem can be solved perfectly well with bash's builtin [[ command:

if [[ ":$PATH:" == *":$HOME/bin:"* ]]; then
...

Note that adding colons before both the expansion of $PATH and the path to search for solves the substring match issue; double-quoting the path avoids trouble with metacharacters.

Answer 4

Here's how to do it without grep:

if [[ $PATH == ?(*:)$HOME/bin?(:*) ]]

The key here is to make the colons and wildcards optional using the ?() construct. There shouldn't be any problem with metacharacters in this form, but if you want to include quotes this is where they go:

if [[ "$PATH" == ?(*:)"$HOME/bin"?(:*) ]]

This is another way to do it using the match operator (=~) so the syntax is more like grep's:

if [[ "$PATH" =~ (^|:)"${HOME}/bin"(:|$) ]]