Use an alternate value only when a variable is nonempty.
Bash Scripts: The colon-plus expansion returns its word only when the parameter has a nonempty value.
set -euo pipefail
setting=ready
printf "%s\n" "${setting:+configured}"
setting=""
printf "[%s]\n" "${setting:+configured}"Expected output EXAMPLE
configured []
Details
Requires Bash 4 or later. Save as snippet.sh and run bash snippet.sh in an empty working directory. The colon-plus expansion returns its word only when the parameter has a nonempty value.
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
604328dc26077ae5e7d829491a284158359701c2d12291b1bb2a44764c8adb06- 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
configured []
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.