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dact - compress or expand a file or stream


dact [ -dsfcvlniCHOShVNa ] [-b size] [-e algo] [-m file] [-o file] [-u url] [-p url] [-M command]
[-D desc] [-I algo] [-U file] [-E cipher] [file ...]


DACT reduces input files by attempting to compress each block of the file with several
different algorithms and selects the best one for each block.


-d Decompress the file (or stdin, if no file is given), removing the extension if it
has a valid one.

-s Display statistics about the file, such as: Magic number of file, DACT version file
was compressed with, Block size used to compress file, Compressed file size,
Original file's size, Compression ratio (uncompressed to compressed), File's
original name, CRCs (if available).

-f Force bad and unsafe things to happen. Can be combined to make even worse things
happen. One `-f' allows overwriting of existing files, two `-f' allows you to
ignore bad magic and CRC check fails.

-c Send output to stdout, this will allow you to force DACT to send compressed output
to a terminal or result of compressing a file to a pipe.

-v Increase verbosity, can be combined to increase verbosity a lot. Currently, only
up to 3 makes sense. One `-v' displays a bar graph. Two `-v' displays a bar graph
and block information. Three `-v' displays a bar graph and detailed compression
statistics per block.

-l List compression algorithms available.

-n Toggle use of CRCs. This option is especially useful when combined with the
network capabilities of DACT. It allows you to create a compressed file with only
the header pointing to a web page that contains the real DACT file (which normally
has its CRCs checked against the compressed header to ensure they're the same
file), with this option the files do not have to be from the same source (i.e., you
can have an updated copy automatically extend itself.)

-i Read input from standard input instead of /dev/tty. This is used to read user
supplied information like encryption keys and passwords from standard input instead
of the more appropriate method of opening "/dev/tty."

-C Complain when compression errors occur. When a block is selected, it is tested to
ensure that it decompresses back to the original source. If it fails, the
algorithm is not used, with this option you are informed of the failure.

-H Write only header (no data). This option is useful for distributing archives that
need only reside on the internet someplace.

-O Toggle writing original file name in the DACT header. This has no real use that I
know of.

-S Use speed-size as a metric rather than size. This is not implemented yet. This
will make DACT create an optimized compressed file, balancing speed of
decompression with size.

-h Give usage synopsis.

-V Display DACT version.

-N Upgrade DACT. This option will fetch the latest binary from the internet and place
it in $HOME/.dact/ as dact.bin. If you have `binary_check on' in your dact.conf
file, DACT will check for this file and use it. If you have Debian and run `dact
-N' as root the Debian upgrade procedure will upgrade your entire system.

-a DACT modules. This option will fetch the latest modules from the internet and
place them in $HOME/.dact/ in a subdirectory corresponding to your Operating System
and CPU Architecture.

-b size
Use the specified block size to compress the file. The size parameters is in

-e num Exclude an algorithm from being used. This option is useful if you know your
target will not be able to decompress a certain algorithm (you can get their
numbers from the `-l' option.)

-m file
Load another config file. This option will attempt to load the specified file in
addition to the normal files, the options in this file will supersede other

-o file
Alternate output. This option sends output to a file instead of INFILE.dct. The
file can also be a URL or '-' for standard out.

-u url This option will encode an URL in the compressed file's header, this URL will be
tried (and CRCs checked) before attempting to decompress the data in the actual

-p url URLs in DACT can have variables in them that will be expanded when network access
is required, this allows you to test the results of that extrapolation easily.
Variables and their values are:
@@OSNM@@ OS Name (linux, freebsd, sunos, etc)
@@OSVR@@ OS version (2.2.x, 4.2, 5.8, etc)
@@OSVS@@ OS version (short) (2.2, 4.2, 5.8, etc)
@@ARCH@@ Arch (i386, sparc64, sun4u, sun4m, etc)
@@DIST@@ If OSNM=Linux, distribution of Linux.
@@FILE@@ Name of compressed file.
@@DTVR@@ Version of DACT (maj.min.rev)
@@DTVS@@ Version of DACT (short) (maj.min)
@@PASS@@ Prompt for Password
@@USER@@ Prompt for Username
@@ATSN@@ Put an `@'
dact -p
dact: http://www.rkeene.org/devel/dact/precompiled/dact-linux-2.4-i586.bin

-M command
This option executes a command from the command line as if it appeared in

-D desc
Encode the description specified into the header of the compressed file.

-I num Use only 1 algorithm (and uncompressed as a fall-back), useful if you want to limit
yourself to a certain type of compression.

-U file
Encode the specified file into the header of the compressed file. This file will
be searched (line-by-line) for a working URL to download compressed content from.
See also `-u.'

-E cipher
Enable encryption using the specified algorithm, different algorithms use different
authentication methods.

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