gzip: Advanced usage

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1 4 Advanced usage
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1 Multiple compressed files can be concatenated.  In this case, ‘gunzip’
1 will extract all members at once.  If one member is damaged, other
1 members might still be recovered after removal of the damaged member.
1 Better compression can be usually obtained if all members are
1 decompressed and then recompressed in a single step.
1 
1    This is an example of concatenating ‘gzip’ files:
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1      gzip -c file1  > foo.gz
1      gzip -c file2 >> foo.gz
1 
1 Then
1 
1      gunzip -c foo
1 
1 is equivalent to
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1      cat file1 file2
1 
1    In case of damage to one member of a ‘.gz’ file, other members can
1 still be recovered (if the damaged member is removed).  However, you can
1 get better compression by compressing all members at once:
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1      cat file1 file2 | gzip > foo.gz
1 
1 compresses better than
1 
1      gzip -c file1 file2 > foo.gz
1 
1    If you want to recompress concatenated files to get better
1 compression, do:
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1      zcat old.gz | gzip > new.gz
1 
1    If a compressed file consists of several members, the uncompressed
1 size and CRC reported by the ‘--list’ option applies to the last member
1 only.  If you need the uncompressed size for all members, you can use:
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1      zcat file.gz | wc -c
1 
1    If you wish to create a single archive file with multiple members so
1 that members can later be extracted independently, use an archiver such
1 as ‘tar’ or ‘zip’.  GNU ‘tar’ supports the ‘-z’ option to invoke ‘gzip’
1 transparently.  ‘gzip’ is designed as a complement to ‘tar’, not as a
1 replacement.
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