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Top Forums UNIX for Advanced & Expert Users gzip vs pipe gzip: produce different file size Post 302527624 by hanfresco on Friday 3rd of June 2011 09:24:50 PM
Old 06-03-2011
gzip vs pipe gzip: produce different file size

Hi All,

I have a random test file: test.txt, size: 146
$ ll test.txt
$ 146 test.txt

Take 1:
$ cat test.txt | gzip > test.txt.gz
$ ll test.txt.gz
$ 124 test.txt.gz

Take 2:
$ gzip test.txt
$ ll test.txt.gz
$ 133 test.txt.gz

As you can see, gzipping a file and piping into gzip produce different sized *gz files. The problem currently is that some archivers, such as WinZip and Cygwin's gunzip have to unzip the piped gzip file twice before it can be read as a plain text file. Why is this and how can I ensure piping into gzip produces the same file as gzipping a file?

Thanks,
 

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ns_zlib(3aolserver)					     AOLserver Zlib Extension					       ns_zlib(3aolserver)

__________________________________________________________________________________________________________________________________________________

NAME
ns_zlib - Zlib compression support SYNOPSIS
ns_zlib compress string ns_zlib gunzip file ns_zlib gzip string ns_zlib gzipfile file ns_zlib uncompress string _________________________________________________________________ DESCRIPTION
The ns_zlib command enables compressing and uncompressing of strings or files. The command is available if the nszlib.so module is loaded into AOLserver or the libnszlib.so, nszlib.dll, or libnszlib.dylib dynamic library is loaded using the load command in a suitable tclsh such as nstclsh. ns_zlib compress string This command compresses the given string and returns a Tcl byte array object with the compressed data. ns_zlib gunzip file This command uncompresses the contents of the given gzipped file and returns a string as the result. ns_zlib gzipfile file This command is similar to the gzip shell routines, compressing the given file into a new file with the .gz extension. If success- ful, the original uncompressed file is deleted. ns_zlib uncompress bytearray This command takes a byte array object which includes compressed data and returns an uncompressed string object. EXAMPLES
The following examples demonstrate compressing and uncompressing a string; # Compress Tcl string set test "This is test string" set data [ns_zlib compress $test] set test [ns_zlib uncompress $data] --> returns "This is test string" # Compress the string into gzip format set gzip [ns_zlib gzip $test] # Save as gzip file set fd [open /tmp/test.gz w] fconfigure $fd -translation binary -encoding binary puts -nonewline $fd $gzip close $fd # Uncompress gzipped file set test [ns_zlib gunzip /tmp/test.gz] --> returns "This is test string" SEE ALSO
ns_adp_ctl(n), load(n) KEYWORDS
GZIP, compress, uncompress AOLserver 4.5 ns_zlib(3aolserver)
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