Definition
Bash scripting is the practice of writing programs in the bash shell language. A bash script is an ordinary text file that begins with a shebang line — #!/bin/bash — and contains a sequence of commands that the shell executes in order. What turns a sequence of commands into a program is the full set of structured-programming features bash provides: variables and parameter expansion, conditionals with if and case, loops with for and while, functions with their own local scope, and access to positional arguments through $1, $2, and $@.
The shell language was designed to glue programs together rather than implement complex algorithms, and that bias shows. Bash excels at orchestration: running tools, transforming their output, branching on exit codes, and stitching the result into pipelines. It is less suited to numerical work, data structures beyond strings and lists, or anything performance-critical.
Why it matters
How it works
A bash script runs in its own subshell, inheriting the parent environment but with its own variables, working directory, and exit status. The script's exit status is the exit status of its last command unless overridden, and that single integer is how the calling shell — or a CI system, or cron — learns whether the work succeeded. Functions inside the script share the same convention: they communicate success through their return code and their results through standard output, which is why the cleanest bash idiom captures function output with command substitution rather than mutating globals.
The hidden complexities are quoting and word-splitting. By default bash splits any unquoted variable on whitespace, which is the source of most production bugs around filenames with spaces. Defensive scripting always double-quotes variable references, uses set -euo pipefail to fail fast on errors and unset variables, and prefers arrays over delimited strings whenever a list is involved. Shellcheck, the static analyser for shell scripts, catches most of these issues automatically and should be part of any scripting workflow that ships to production.