Find lines common to two sorted files.
Linux Commands: Use comm -12 to suppress the two columns of unmatched lines.
LC_ALL=C comm -12 first.txt second.txtExpected output EXAMPLE
b
Details
Run in Bash on GNU/Linux in a scratch directory. Tested with the GNU utilities supplied by Ubuntu. Use comm -12 to suppress the two columns of unmatched lines.
Both inputs must be sorted using the same locale as comm.
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; sed 4.9-2ubuntu0.24.04.1
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Unprivileged snippet process, external networking disabled, read-only root filesystem, and a fresh temporary working directory. 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) / C.UTF-8
- Interpreter invocation
bash -euo pipefail -c <published code>- Container image ID
sha256:32dc2d998158b6554c99b73b533f423696a0f3e31e8cbea9db10b5eee9a2fadd- Code SHA-256
0b9c3d43d0ccb56528ae6aa873a54b8629f8f3a8f7a89c8bc1bbef655c1e890e- Dependencies
- bash 5.2.21-2ubuntu4; coreutils 9.4-3ubuntu6.3; sed 4.9-2ubuntu0.24.04.1
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 'a\nb\n' > first.txt; printf 'b\nc\n' > second.txt
Observed standard output
b
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.