lz4/programs/lz4.1

\."
\." lz4.1: This is a manual page for 'lz4' program. This file is part of the
\." lz4 <http://www.lz4.org/> project.
\." Author: Yann Collet
\."
.
\." No hyphenation
.hy 0
.nr HY 0
.
.TH lz4 "1" "2015-03-21" "lz4" "User Commands"
.SH NAME
\fBlz4, unlz4, lz4cat\fR \- Compress or decompress .lz4 files

.SH SYNOPSIS
.TP 5
\fBlz4\fR [\fBOPTIONS\fR] [-|INPUT-FILE] <OUTPUT-FILE>
.PP
.B unlz4
is equivalent to
.BR "lz4 \-d" 
.br
.B lz4cat
is equivalent to
.BR "lz4 \-dc" 
.br
.PP
When writing scripts that need to decompress files,
it is recommended to always use the name
.B lz4
with appropriate arguments
.RB ( "lz4 \-d"
or
.BR "lz4 \-dc" )
instead of the names
.B unlz4
and
.BR lz4cat .


.SH DESCRIPTION
.PP
\fBlz4\fR is an extremely fast lossless compression algorithm,
based on \fBbyte-aligned LZ77\fR family of compression scheme.
\fBlz4\fR offers compression speeds of 400 MB/s per core, linearly scalable with multi-core CPUs. 
It features an extremely fast decoder, with speed in multiple GB/s per core,
typically reaching RAM speed limit on multi-core systems. 
.B lz4
supports a command line syntax similar to
.BR gzip (1).
The native file format is the
.B .lz4
format.

.SS "Concatenation of .lz4 files"
It is possible to concatenate
.B .lz4
files as is.
.B lz4
will decompress such files as if they were a single
.B .lz4
file. For example:
  lz4 file1  > foo.lz4
  lz4 file2 >> foo.lz4
 then
  lz4cat foo.lz4
 is equivalent to :
  cat file1 file2

.PP

.SH OPTIONS
.
.SS "Short commands concatenation"
In some cases, some options can be expressed using short command
.B "-x"
or long command
.B "--long-word" .
Short commands can be concatenated together. For example,
.B "-d -c"
is equivalent to
.B "-dc" .
Long commands cannot be concatenated.
They must be clearly separated by a space.
.SS "Multiple commands"
When multiple contradictory commands are issued on a same command line,
only the latest one will be applied.
.
.SS "Operation mode"
.TP
.BR \-z ", " \-\-compress
Compress.
This is the default operation mode 
when no operation mode option is specified ,
no other operation mode is implied from the command name 
(for example,
.B unlz4
implies
.B \-\-decompress ),
nor from the input file name
(for example, a file extension
.B .lz4
implies
.B \-\-decompress
by default).
.B -z
can also be used to force compression of an already compressed
.B .lz4
file.
.TP
.BR \-d ", " \-\-decompress ", " \-\-uncompress
Decompress.
.B --decompress
is also the default operation when the input filename has an
.B .lz4
extensionq
.TP
.BR \-t ", " \-\-test
Test the integrity of compressed
.B .lz4
files.
The decompressed data is discarded.
No files are created nor removed.
.
.SS "Operation modifiers"
.TP
.B \-1
 fast compression (default)
.TP
.B \-9
 high compression

.TP
.BR \-f ", " --[no-]force
 This option has several effects:
.RS
.IP \(bu 3
If the target file already exists,
overwrite it without prompting.
.IP \(bu 3
When used with
.B \-\-decompress
and
.B lz4
cannot recognize the type of the source file,
copy the source file as is to standard output.
This allows
.B lz4cat
.B \-\-force
to be used like
.BR cat (1)
for files that have not been compressed with
.BR lz4 .
.RE

.TP
.BR \-c ", " \--stdout ", " \--to-stdout
 force write to standard output, even if it is the console

.TP
.BR \-m ", " \--multiple
 Multiple file names.
 By default, the second filename is used as the output filename for the compressed file.
 With
.B -m
, you can specify any number of input filenames. Each of them will be compressed
independently, and the resulting name of the compressed file will be
.B filename.lz4
.

.TP
.B \-B#
 block size [4-7](default : 7)
 B4= 64KB ; B5= 256KB ; B6= 1MB ; B7= 4MB
.TP
.B \-BD
 block dependency (improve compression ratio)
.TP
.B \--[no-]frame-crc
 select frame checksum (default:enabled)
.TP
.B \--[no-]content-size
 header includes original size (default:not present)
 Note : this option can only be activated when the original size can be determined,
hence for a file. It won't work with unknown source size, such as stdin or pipe.
.TP
.B \--[no-]sparse 
 sparse mode support (default:enabled on file, disabled on stdout)
.TP
.B \-l
 use Legacy format (useful for Linux Kernel compression)
.
.SS "Other options"
.TP
.BR \-v ", " --verbose
 verbose mode
.TP
.BR \-q ", " --quiet
 suppress warnings; specify twice to suppress errors too
.TP
.B \-h/\-H
 display help/long help and exit
.TP
.BR \-V ", " \--version
 display Version number and exit
.TP
.BR \-k ", " \--keep
 Don't delete source file.
This is default behavior anyway, so this option is just for compatibility with gzip/xz.
.TP
.B \-b
 benchmark file(s)
.TP
.B \-i#
 iteration loops [1-9](default : 3), benchmark mode only

.SH BUGS
Report bugs at: https://github.com/Cyan4973/lz4/issues

.SH AUTHOR
Yann Collet