Track 04 of 12 · Automate with intent
Shell Scripts & Job Control
Turn reliable commands into maintainable scripts and control long-running work from an interactive shell. Practice explicit arguments, failures, jobs, and cleanup.
Ten concepts, in learning order
Each lesson assumes the ideas above it and prepares you for the ones below.
- 01Shell script and shebangA shell script is a text file containing shell-language commands, and an executable script's initial #! line asks the operating system to launch a specified interpreter with that file.
- 02Executable permissionThe execute permission bit allows an eligible user to request execution of a regular file and allows traversal or lookup through a directory, subject to other access controls.
- 03Positional and special parametersPositional parameters hold a script or function's arguments, while special parameters expose related state such as argument count, last status, process identity, and all arguments.
- 04Shell functionsA shell function is a named compound command that runs in the current shell environment with its own positional parameters and returns a shell exit status.
- 05Shell conditionalsShell conditionals choose commands by evaluating the exit status of command lists, including test utilities and pattern-based case clauses.
- 06Shell loopsShell for, while, and until constructs repeatedly execute command lists over an argument sequence or while a status condition holds.
- 07Sourcing vs subprocess executionSourcing reads commands into the current shell environment, while executing a script normally runs it in a separate process and cannot directly modify the parent's shell state.
- 08Shell error handlingShell error handling combines explicit status checks, intentional propagation, validated inputs, cleanup, and selectively enabled shell options rather than relying on exceptions.
- 09Foreground, background, and jobsInteractive shell job control groups pipeline processes into jobs and manages which job owns the controlling terminal's foreground process group.
- 10Signals and trapsA signal is an asynchronous notification delivered to a process, while a shell trap arranges for shell code to run when selected signals or synthetic events such as EXIT occur.
Continue the curriculum
Next: Processes & Filesystems
Understand how Unix-like systems identify running programs and connect names, metadata, permissions, and open files. These concepts explain what common process and filesystem commands are actually inspecting or changing.
Open track 5