Advanced usage (GNU Gzip)
Next: Environment, Previous: Invoking gzip
, Up: GNU Gzip: General file (de)compression [Contents][Index]
4 Advanced usage
Multiple compressed files can be concatenated. In this case, gunzip
will extract all members at once. If one member is damaged, other members might still be recovered after removal of the damaged member. Better compression can be usually obtained if all members are decompressed and then recompressed in a single step.
This is an example of concatenating gzip
files:
gzip -c file1 > foo.gz gzip -c file2 >> foo.gz
Then
gunzip -c foo
is equivalent to
cat file1 file2
In case of damage to one member of a ‘.gz
’ file, other members can still be recovered (if the damaged member is removed). However, you can get better compression by compressing all members at once:
cat file1 file2 | gzip > foo.gz
compresses better than
gzip -c file1 file2 > foo.gz
If you want to recompress concatenated files to get better compression, do:
zcat old.gz | gzip > new.gz
If a compressed file consists of several members, the uncompressed size and CRC reported by the --list
option applies to the last member only. If you need the uncompressed size for all members, you can use:
zcat file.gz | wc -c
If you wish to create a single archive file with multiple members so that members can later be extracted independently, use an archiver such as tar
or zip
. GNU tar
supports the -z
option to invoke gzip
transparently. gzip
is designed as a complement to tar
, not as a replacement.
Next: Environment, Previous: Invoking gzip
, Up: GNU Gzip: General file (de)compression [Contents][Index]