has checks presence of various command line tools on the path and also reports their installed version

Download the has file. There is no dependency apart from bash itself

$ has node npm java git gradle 
✔ node 8.2.1
✔ npm 5.3.0
✔ java 1.8.0
✔ git 2.14.1
✔ gradle 4.0.1

If everything is good has exits with status code 0. The status code reflects number of commands not found on your path.

$ has node go javac
✔ node 8.2.1
✔ go 1.8.3
✘ javac

And echo the status:

$ echo $?
1

Just download the has script in your path.

git clone https://github.com/kdabir/has.git && cd has && make install

If you are lazy, you can run has directly off the internet as well:

curl -sL https://git.io/_has | bash -s git node npm
✔ git 2.14.1
✔ node 8.2.1
✔ npm 5.3.0

And if that's too much of typing every time, setup an alias

alias has="curl -sL https://git.io/_has | bash -s"

And use it

$ has git
✔ git 2.14.1

Let's say $ has foobar returns foobar not understood, because has may not have whitelisted foobar.

In such cases, pass HAS_ALLOW_UNSAFE=y has foobar. This is should still check for existance of foobar and tries to detect version as well.

1. Star the repo, tweet about it, spread the word
2. Update the documentation (i.e. the README file)
3. Adding support for more commands
4. Adding more features to has