NAME

       snappy, unsnappy — Snappy compression and decompression with and without framing

SYNOPSIS

       snappy [-f] [file] > snappy.sn|.sz

       snappy -d [-i] [file]
       unsnappy [-i] [file]

DESCRIPTION

       Without  -d,  compresses  file  (standard  input  stream if "-", the default) with Snappy to the standard
       output stream, then assesses the compression ratio achieved to the standard error stream.
       With -f, the Snappy framing format is produced.

       When run as unsnappy, or with -d, decompresses file (likewise) from Snappy, or the Snappy framing  format
       (detected automatically), to the standard output stream.
       With -i, decompression and framing errors are ignored and processing continues.

       As  a  format limitation, if file isn't seekable when producing or decompressing unframed Snappy streams,
       it will be read into memory in its entirety.

EXIT STATUS

       1  If a decompression error (invalid or truncated Snappy block) or a  framing  error  (Stream  identifier
          (0xFF)  frame  invalid,  unknown reserved unskippable chunk ([0x02, 0x7F]) frame encountered, checksum
          mismatch).
       2  On an I/O error.
       3  When compressing without -f and file is larger than 4GiB.  (Output unaffected, but see “BUGS”.)

DIAGNOSTICS

       After compressing,
             data: 2048576 -> 1099105 (53.65%)
       means that the file data was 2048576 bytes, which were compressed down to 1099105 bytes, and  the  output
       is thus 53.65% the size.

SEE ALSO

       The Snappy homepage: https://google.github.io/snappy/

CONFORMING TO

       The  framed  format,  with  MIME  type  ‘application/x-snappy-framed’, version 2013-10-25: Snappy framing
       format description: https://github.com/google/snappy/blob/main/framing_format.txt.

       The unframed format, as described in Snappy  compressed  format  description:  https://github.com/google/
       snappy/blob/main/format_description.txt, as provided by the upstream Fast Compressor/Decompressor Library
       (libsnappy, -lsnappy).

BUGS

       The  largest  representable  unframed  stream  is of size 4GiB-1B (= 4·1024·1024·1024B-1B = 4294967295B).
       Above this size the length stored in the header becomes  mangled,  so  the  stream  may  be  semantically
       correct  but  will  produce  an incorrect (short) output when decompressing.  snappy warns about this and
       exits 3.

       On 32-bit systems it is impossible to produce unframed streams from files larger than 4GiB-1B at all  due
       to  an API limitation (“EXIT STATUS 2”).  On 32-bit systems the output size and compression ratio will be
       misrepresented if compression produces an unframed output larger than 4GiB-1B.  It is also impossible  to
       decompress such files there.

       Supposedly, compressors which produce checksums with inverted byte order exist in the wild.

snappy-tools 1-1                                February 15, 2024                                      SNAPPY(1)