Luckily, nearly all systems have an env program installed in /usr/bin. There is a program that can do a PATH search for you, though, it's called env. The kernel won't (some might) do a PATH search for you. The idea is that you install your programs in one of the directories that are in PATH and the system should be able to find your program when you want to run it by name.

POSIX already has a mechanism for dealing with that: PATH. To write a portable bash script, we can therefore not rely on hard-coding the location of the bash program. While on Linux machines it usually is, there are a range of other POSIX machines where bash ships in various locations, such as /usr/xpg/bin/bash or /usr/local/bin/bash. Unfortunately, bash is not always shipped by default, and it is not always available in /bin. The result is that the kernel will run the program /bin/bash to interpret the script. Most commonly, you'll see hash bangs like so: #!/bin/bash (In reality, the kernel will often use the user's default shell to interprete the file, which is very dangerous because it might not be the right interpreter at all or it might be able to parse some of it but with subtle behavioural differences such as is the case between sh and bash).

It could be bash, perl, python, sh, or something else. If it doesn't, you're not telling the kernel what it is, and therefore the kernel doesn't know what program to use to interprete it. That means every script that is executable should have a hashbang. Then, the script is passed to the program (as second argument) along with all the arguments you gave the script as subsequent arguments.

The hashbang tells the kernel what program to run (in this case the command /usr/bin/env is ran with the argument bash). It should contain a hashbang: #! /usr/bin/env bash For non-binaries, this is done by looking at the first line of the file. When a file is executable, the kernel is responsible for figuring out how to execte it. To make a script executable, give it the necessary permission: chmod +x bar To start an executable (which is any file with executable permission) you just specify it by its path: /foo/bar To run a non-executable bash script, use: bash myscript To run a non-executable sh script, use: sh myscript

Run script on mac terminal