Which command re-runs `df -h` every 5 seconds and redraws the result in place?
LPIC-1 Exam 101-500, objective 103. GNU and Unix commands easy
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The options
Not correct watch -t 5 df -h
Wrong flag. In watch, -t (--no-title) suppresses the header line; it does not set the interval.
Correct watch -n 5 df -h
Correct. watch repeats a command at an interval, clearing the screen between runs. -n sets the interval in seconds; the default is 2.
Not correct top -d 5 df -h
Wrong. top -d does set a refresh delay, but top displays the process table — it cannot run an arbitrary command for you.
Not correct repeat 5 df -h
Wrong. There is no standard repeat command in bash (tcsh has one, and it would mean 'run 5 times', not 'every 5 seconds').
Why
`watch -n <seconds> <command>` is the standard way to observe something change over time. Quote the command if it contains pipes or shell metacharacters, otherwise the shell applies them to watch itself.
Where this comes from
- Cited
- LPI exam objective 103.5
- What it says
- Monitor processes and system state repeatedly with watch.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 103 and space the ones you get wrong.