Capture standard output and standard error separately.
Bash Scripts: Use distinct redirections when diagnostic text should not be mixed with data.
set -euo pipefail
bash -c 'printf "data\n"; printf "warning\n" >&2' > output.txt 2> error.txt
printf "stdout: %s\n" "$(cat output.txt)"
printf "stderr: %s\n" "$(cat error.txt)"Expected output EXAMPLE
stdout: data stderr: warning
Details
Requires Bash 4 or later. Save as snippet.sh and run bash snippet.sh in an empty working directory. Use distinct redirections when diagnostic text should not be mixed with data.
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
ef62634350b90ddc790a87e59dd686e6992cdab7e5684db5e5aefe10ffbdde9b- 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
stdout: data stderr: warning
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.