Keep loop state by avoiding a pipeline subshell.
Bash Scripts: Redirect input into a while loop so updates to a counter remain in the current shell.
set -euo pipefail
count=0
while IFS= read -r line; do count=$((count + 1)); done < lines.txt
printf "%s\n" "$count"Expected output EXAMPLE
3
Details
Requires Bash 4 or later. Save as snippet.sh and run bash snippet.sh in an empty working directory. Redirect input into a while loop so updates to a counter remain in the current shell.
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
d6f7508c740a373f73e53a614c82b5c5760e81c447bb15683474d1745cd18079- 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.
printf 'one\ntwo\nthree\n' > lines.txt
Observed standard output
3
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.