programming-shell

Shell Programming

Shell Scripts owns script mechanics, and Shell Standards owns every shell stack rule. Test-Driven Development and Test Boundaries and Gates govern tests and gates, Red, Green, Refactor runs each cycle, and Developing Applications carries the judgement that holds in every language. This skill adds only the procedure and judgement of applying them in shell. Where a sentence here seems to state a rule, the standards decide.

Start From the First Line

Read the interpreter line and the strict-mode setting before anything else; they decide which dialect's rules apply. Run the analyser, the formatter check, and the script's tests on the untouched tree. A gate already failing is handled under Preexisting Error Resolution. For a dialect the analyser cannot read, the syntax check passes and you carry the review the analyser would have done.

Decide Whether It Belongs in Shell

Before adding logic, ask what the addition is. Running commands in order, passing files between them, and stopping on failure is shell's job. Parsing a structured format beyond a single jq query, computing over data, retrying with backoff, or branching on many cases is logic; once a change adds some, the standard's size rule decides whether the script moves to a language with a unit layer. Raise it before writing the logic, not after.

Trace Where Exit-on-Error Does Not Reach

Strict mode stops the script at a failing command only where the shell checks it. Read each change for the places the standard lists: a function called as a condition, a command on the left of && or ||, a declaration assigned from a substitution, and a substitution in a shell that does not inherit the setting. At each one, ask what happens when the command fails. If the answer is that the script carries on, check the status explicitly.