Distinguish an empty input line from end of input.
Bash Scripts: A successful read can return an empty value; its status indicates whether a line was read.
set -euo pipefail
if IFS= read -r line < empty-line.txt; then
printf "Read %s characters\n" "${#line}"
fiExpected output EXAMPLE
Read 0 characters
Details
Requires Bash 4 or later. Save as snippet.sh and run bash snippet.sh in an empty working directory. A successful read can return an empty value; its status indicates whether a line was read.
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
4f74e07bf989ecaba02cb13b6ebde811f9b782cbfaa692ee8cb4e5b84a89bc92- 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 '\n' > empty-line.txt
Observed standard output
Read 0 characters
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.