use_bash.md

Use bash

These might need to be broken into separate TILs for ease of navigation

A good cheat sheet can be found in this blog post

Find Substrings in Bash

https://linuxize.com/post/how-to-check-if-string-contains-substring-in-bash/ https://www.baeldung.com/linux/string-contains-substring

Quotes

https://www.grymoire.com/Unix/Quote.html

error conditional binary operator expected in compound branch

https://unix.stackexchange.com/questions/435193/error-conditional-binary-operator-expected-in-compound-branch

Split Strings

https://www.delftstack.com/howto/linux/split-string-in-bash/#using-ifs-to-split-a-string-in-bash

Use Booleans

How can I declare and use Boolean variables in a shell script?

Bash if, then, else

https://linuxize.com/post/bash-if-else-statement/

Handle empty element in array

https://stackoverflow.com/questions/41893336/replace-empty-element-in-bash-array

Syntax error: redirection unexpected

If you observe the following error

Syntax error: redirection unexpected

It is due to your Bash script is being executing by a non-bash interpreter, e.g. sh or similar.

You might have specified the shebang line in your shell script file:

#!/bin/bash

But if it is executed as:

sh myscript.sh

The shebang line is overridden by the interpreter specified on the command line.

I observed this issue in a Dockerfile, where the entrypoint was specified as:

ENTRYPOINT ["/bin/sh", "/entrypoint.sh"]

So when I introduced more Bash in my entrypoint.sh I was doomed. Changing the interpreter in the Dockerfile fixed the issue.

ENTRYPOINT ["/bin/bash", "/entrypoint.sh"]

Answer lifted from StackOverflow example lifted from rojopolis/spellcheck-github-actions. Do also see the reference Docker documentation