What does the colon do in PATH

Question

I am new to bash, and I saw people often add : after a directory when modifying PATH. After searching for a while, I did not find an answer for that, or I believe I did not search it correctly. So I hope I could get an answer here.

Example:

/Users/chengluli/anaconda/bin:/Users/chengluli/.rbenv/shims:/ 

What does the : after bin and shims do?

Answer 1

: is the separator. The PATH variable is itself a list of folders that are "walked" through when you run a command.

In this case, the folders on your PATH are:

• /Users/chengluli/anaconda/bin
• /Users/chengluli/.rbenv/shims
• /

Answer 2

As others have said, the : is a separator (Windows uses a semi-colon ;). But you are probably thinking of a trailing colon : at the end of the PATH variable. For example:

/Users/chengluli/anaconda/bin:/Users/chengluli/.rbenv/shims: 

From the bash man pages:

A zero-length (null) directory name in the value of PATH indicates the current directory. A null directory name may appear as two adjacent colons, or as an initial or trailing colon.

Putting the current directory in the PATH is generally considered a security risk and a bad idea. It is particularly dangerous when using the root user.

By the way, bash only uses $PATH on the first call of an external program, after that it uses a hash table. See man bash and the hash command