/srv/link is a symbolic link pointing at /srv/data/report.txt, which exists and is an ordinary file. Which THREE test expressions return a true exit status? (Choose three.)
LPIC-1 Exam 102-500, objective 105. Shells and shell scripting hard
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How these questions are written — where each question comes from, what the verification ledger records, and what happens when one is found wrong.
The options
Choose 3.
Correct [ -L /srv/link ]
Correct. -L is the one test that does not follow the link: it is true because /srv/link is itself a symbolic link.
Correct [ -e /srv/link ]
Correct. -e follows the link and asks whether the target exists, which it does. This test would be false for a dangling link.
Correct [ -f /srv/link ]
Correct. -f also follows the link, and the target is an ordinary file, so the expression is true even though the name given is a link.
Not correct [ -d /srv/link ]
Wrong. After following the link the target is a regular file, not a directory, so -d is false.
Not correct [ -p /srv/link ]
Wrong. -p is true only for a named pipe (FIFO). The target here is an ordinary file.
Why
Nearly every file test dereferences symbolic links and reports on the target, which is why -f and -e are true for a link to a regular file; -L, and its synonym -h, are the exceptions that report on the link itself. The practical consequence is that -e is false for a broken link while -L is true, so [ -L f ] && [ ! -e f ] is the idiom for detecting a dangling link. The same distinction separates stat from stat -L and ls -l from ls -lL.
Where this comes from
- Cited
- manual page test(1)
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 105 and space the ones you get wrong.
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