LPIC-1 Shells, Scripting and Data Management Practice Question
A script produces both standard output and error messages. An administrator wants to save the output to 'out.log' and the error messages to 'err.log', but also wants to see both on the terminal. Which command achieves this?
⚠ Common exam trap
Many exam-takers confuse `2>&1` (which merges stderr into stdout) with separate stream handling, leading them to pick options that either lose terminal output or fail to keep stdout and stderr in distinct files.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
./script.sh > >(tee out.log) 2> >(tee err.log)
Uses process substitution to redirect stdout and stderr into separate tee commands, which both write to files and pass the streams through to the terminal. The syntax `> >(tee out.log)` redirects stdout to a tee process that writes to out.log and also echoes to the terminal, while `2> >(tee err.log)` does the same for stderr. This ensures both streams are saved to separate files and displayed on the terminal simultaneously.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
./script.sh 2>&1 | tee out.log 2>&1 | tee err.log
Why it's wrong here
Complex and does not separate streams; stderr gets merged into stdout repeatedly.
- ✓
./script.sh > >(tee out.log) 2> >(tee err.log)
Why this is correct
Uses process substitution to duplicate stdout to terminal and out.log, and stderr to terminal and err.log.
- ✗
./script.sh > out.log 2> err.log
Why it's wrong here
Saves output and errors to separate files but does not display anything on the terminal.
- ✗
./script.sh 2>&1 | tee out.log
Why it's wrong here
Merges stderr into stdout; both go to out.log and terminal, but errors are not separated.
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Written by Johnson Ajibi, MSc IT Security
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