has

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

How ?

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.