Why do you need to put bin bash at the beginning of a script file

Question

It's a convention so the *nix shell knows what kind of interpreter to run.

For example, older flavors of ATT defaulted to sh (the Bourne shell), while older versions of BSD defaulted to csh (the C shell).

Even today (where most systems run bash, the "Bourne Again Shell"), scripts can be in bash, python, perl, ruby, PHP, etc, etc. For example, you might see #!/bin/perl or #!/bin/perl5.

PS: The exclamation mark (!) is affectionately called "bang". The shell comment symbol (#) is sometimes called "hash".

PPS: Remember - under *nix, associating a suffix with a file type is merely a convention, not a "rule". An executable can be a binary program, any one of a million script types and other things as well. Hence the need for #!/bin/bash.

Answer 1

It's a show so the *nix shell understands what sort of mediator to run.

For instance, more established kinds of ATT defaulted to sh (the Bourne shell), while more seasoned renditions of BSD defaulted to csh (the C shell).

Indeed, even today (where most frameworks run slam, the "Bourne Again Shell"), contents can be in slam, python, perl, ruby, PHP, and so forth, and so on. For instance, you could see #!/canister/perl or #!/receptacle/perl5.

PS: The interjection mark (!) is lovingly called "bang". The shell remark image (#) is once in a while called "hash".

PPS: Remember - under *nix, partner a postfix with a record type is only a show, not a "rule". An executable can be a parallel program, any of 1,000,000 content sorts and different things too. Consequently the requirement for #!/container/bash.505

It's a show so the *nix shell understands what sort of translator to run.

For instance, more seasoned kinds of ATT defaulted to sh (the Bourne shell), while more seasoned variants of BSD defaulted to csh (the C shell).

Indeed, even today (where most frameworks run slam, the "Bourne Again Shell"), contents can be in slam, python, perl, ruby, PHP, and so on, and so on. For instance, you could see #!/container/perl or #!/receptacle/perl5.

PS: The interjection mark (!) is tenderly called "bang". The shell remark image (#) is some of the time called "hash".

PPS: Remember - under *nix, partner a postfix with a document type is just a show, not a "rule". An executable can be a parallel program, any of 1,000,000 content sorts and different things too. Consequently the requirement for #!/container/slam.