bash - Detect if PATH has a specific directory entry 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

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
  echo "Your path is correctly set"
else
  echo "Your path is missing ~/bin, you might want to add it."
fi

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.