perlio::gzip(3) [osx man page]

gzip(3) 						User Contributed Perl Documentation						   gzip(3)

NAME

       PerlIO::gzip - Perl extension to provide a PerlIO layer to gzip/gunzip

SYNOPSIS

	 use PerlIO::gzip;
	 open FOO, "<:gzip", "file.gz" or die $!;
	 print while <FOO>; # And it will be uncompressed...

	 binmode FOO, ":gzip(none)" # Starts reading deflate stream from here on

DESCRIPTION

       PerlIO::gzip provides a PerlIO layer that manipulates files in the format used by the "gzip" program.  Compression and Decompression are
       implemented, but not together.  If you attempt to open a file for reading and writing the open will fail.

EXPORT

       PerlIO::gzip exports no subroutines or symbols, just a perl layer "gzip"

LAYER ARGUMENTS

       The "gzip" layer takes a comma separated list of arguments. 4 exclusive options choose the header checking mode:

       gzip
	   The default.  Expects a standard gzip file header for reading, writes a standard gzip file header.

       none
	   Expects or writes no file header; assumes the file handle is immediately a deflate stream (eg as would be found inside a "zip" file)

       auto
	   Potentially dangerous. If the first two bytes match the "gzip" header "x1fx8b" then a gzip header is assumed (and checked) else a
	   deflate stream is assumed.  No different from gzip on writing.

       autopop
	   Potentially dangerous. If the first two bytes match the "gzip" header "x1fx8b" then a gzip header is assumed (and checked) else the
	   layer is silently popped.  This results in gzip files being transparently decompressed, other files being treated normally.	Of course,
	   this has sides effects such as File::Copy becoming gunzip, and File::Compare comparing the uncompressed contents of files.

	   In autopop mode Opening a handle for writing (or reading and writing) will cause the gzip layer to automatically be popped.

       Optionally you can add this flag:

       lazy
	   For reading, defer header checking until the first read.  For writing, don't write a header until the first buffer empty of compressed
	   data to disk.  (and don't write anything at all if no data was written to the handle)

	   By default, gzip header checking is done before the "open" (or "binmode") returns, so if an error is detected in the gzip header the
	   "open" or "binmode" will fail.  However, this will require reading some data, or writing a header.  With lazy set on a file opened for
	   reading the check is deferred until the first read so the "open" should always succeed, but any problems with the header will cause an
	   error on read.

	     open FOO, "<:gzip(lazy)", "file.gz" or die $!; # Dangerous.
	     while (<FOO>) {
	       print;
	     } # Whoa. Bad. You're not distinguishing between errors and EOF.

	   If you're not careful you won't spot the errors - like the example above you'll think you got end of file.

	   lazy is ignored if you are in autopop mode.

AUTHOR

       Nicholas Clark, <nwc10+perlio-gzip@colon.colondot.net>

SEE ALSO

       perl, gzip, rfc 1952 <http://www.ietf.org/rfc/rfc1952.txt> (the gzip file format specification), rfc 1951
       <http://www.ietf.org/rfc/rfc1951.txt> (DEFLATE compressed data format specification)

perl v5.16.2							    2006-10-01								   gzip(3)

GZIP(1) 						    BSD General Commands Manual 						   GZIP(1)

NAME

     gzip -- compression/decompression tool using Lempel-Ziv coding (LZ77)

SYNOPSIS

     gzip [-cdfhlNnqrtVv] [-S suffix] file [file [...]]
     gunzip [-cfhNqrtVv] [-S suffix] file [file [...]]
     zcat [-fhV] file [file [...]]

DESCRIPTION

     The gzip program compresses and decompresses files using Lempel-Ziv coding (LZ77).  If no files are specified, gzip will compress from stan-
     dard input, or decompress to standard output.  When in compression mode, each file will be replaced with another file with the suffix, set by
     the -S suffix option, added, if possible.	In decompression mode, each file will be checked for existence, as will the file with the suffix
     added.

     If invoked as gunzip then the -d option is enabled.  If invoked as zcat or gzcat then both the -c and -d options are enabled.

     This version of gzip is also capable of decompressing files compressed using compress(1) or bzip2(1).

OPTIONS

     The following options are available:

     -1, --fast

     -2

     -3

     -4

     -5

     -6

     -7

     -8

     -9, --best        These options change the compression level used, with the -1 option being the fastest, with less compression, and the -9
		       option being the slowest, with optimal compression.  The default compression level is 6.

     -c, --stdout, --to-stdout
		       This option specifies that output will go to the standard output stream, leaving files intact.

     -d, --decompress, --uncompress
		       This option selects decompression rather than compression.

     -f, --force       This option turns on force mode.  This allows files with multiple links, overwriting of pre-existing files, reading from or
		       writing to a terminal, and when combined with the -c option, allowing non-compressed data to pass through unchanged.

     -h, --help        This option prints a usage summary and exits.

     -l, --list        This option displays information about the file's compressed and uncompressed size, ratio, uncompressed name.  With the -v
		       option, it also displays the compression method, CRC, date and time embedded in the file.

     -N, --name        This option causes the stored filename in the input file to be used as the output file.

     -n, --no-name     This option stops the filename and timestamp from being stored in the output file.

     -q, --quiet       With this option, no warnings or errors are printed.

     -r, --recursive   This option is used to gzip the files in a directory tree individually, using the fts(3) library.

     -S suffix, --suffix suffix
		       This option changes the default suffix from .gz to suffix.

     -t, --test        This option will test compressed files for integrity.

     -V, --version     This option prints the version of the gzip program.

     -v, --verbose     This option turns on verbose mode, which prints the compression ratio for each file compressed.

ENVIRONMENT

     If the environment variable GZIP is set, it is parsed as a white-space separated list of options handled before any options on the command
     line.  Options on the command line will override anything in GZIP.

SEE ALSO

     bzip2(1), compress(1), xz(1), fts(3), zlib(3)

HISTORY

     The gzip program was originally written by Jean-loup Gailly, licensed under the GNU Public Licence.  Matthew R. Green wrote a simple front
     end for NetBSD 1.3 distribution media, based on the freely re-distributable zlib library.	It was enhanced to be mostly feature-compatible
     with the original GNU gzip program for NetBSD 2.0.

     This manual documents NetBSD gzip version 20040427.

AUTHORS

     This implementation of gzip was written by Matthew R. Green <mrg@eterna.com.au>.

BSD
								   June 18, 2011							       BSD