Validate the number of positional arguments.
Bash Scripts: Use the argument count to enforce a simple command-line contract.
set -euo pipefail
set -- input.txt output.txt
if (($# != 2)); then
printf "Expected two arguments\n" >&2
exit 2
fi
printf "%s -> %s\n" "$1" "$2"Expected output EXAMPLE
input.txt -> output.txt
Details
Requires Bash 4 or later. Save as snippet.sh and run bash snippet.sh in an empty working directory. Use the argument count to enforce a simple command-line contract.
Tested on Ubuntu 24.04.5 LTS · · GNU bash, version 5.2.21(1)-release (x86_64-pc-linux-gnu) · bash 5.2.21-2ubuntu4; coreutils 9.4-3ubuntu6.3
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Snippet process uid 65534 with a read-only root filesystem and temporary working files. Networking disabled. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged process) / C.UTF-8
- Interpreter invocation
bash -euo pipefail -c <published code>- Container image ID
sha256:ec91410a8f6ec3e985830b5e3a0560306d36f8c1c5ccd91a6699abe707123fa3- Code SHA-256
901a8c3b2b55ba5a84f302282dce87cf63f29d54e7e6eb25cc1400484bf5eab8- Dependencies
- bash 5.2.21-2ubuntu4; coreutils 9.4-3ubuntu6.3
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
# No input files required.
Observed standard output
input.txt -> output.txt
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.