A partition is nearly full and you have been sent access.log.gz. You need to read its contents on stdout without leaving an uncompressed copy on disk and without destroying the compressed file. Which command does that?
LPIC-1 Exam 101-500, objective 103. GNU and Unix commands medium
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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
Correct zcat access.log.gz
Correct. zcat decompresses to standard output and leaves the .gz file exactly as it was, so nothing extra is written to the filesystem.
Not correct gunzip access.log.gz
Wrong for both requirements. gunzip writes the decompressed access.log to disk and removes access.log.gz once it succeeds.
Not correct gzip -l access.log.gz
Wrong. -l lists the compressed size, uncompressed size and compression ratio of the archive. It never shows the data.
Not correct xzcat access.log.gz
Wrong compressor. xzcat expects the xz container; handed a gzip stream it reports an unsupported or corrupt file format.
Why
Each compressor ships a cat-style front end that decompresses to standard output and touches nothing on disk: zcat for gzip, bzcat for bzip2, xzcat for xz. They are the safe way to feed compressed logs into a pipeline, as in `zcat access.log.gz | grep 404 | wc -l`. gunzip -c and gzip -dc are equivalent spellings of zcat.
Where this comes from
- Cited
- manual page gzip(1)
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 103 and space the ones you get wrong.
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