The .sit extension usually accompanies archives created with Aladdin Systems’ StuffIt archiver for Mac OS. Those files may have additional .hqx or .bin extensions indicating that they have been processed with BinHex or MacBinary utilities to create a single text or binary file which can be transferred electronically over computer networks. (Macintosh files often have two parts, called forks, that must be joined together before transfer to make sure that they are transferred as a whole.) You can handle such encoded files with utilities form the macutil package, which is free and available for all decent Linux distributions).
Since Aladdin Systems controls the source code for StuffIt, your only choice when you receive an .sit file is to use the Aladdin Expander for Linux, which is currently in beta (but quite usable). Aladdin Systems has made the beta available to the public as freeware: you do not have to pay cash for it, but you do not get access to the source code either. Currently there are no tools for Linux that will create .sit archives.
To decompress an .sit archive, type unstuff archive.sit. The extracted files will go into the present working directory unless you use the -d option, which lets you specify the destination directory: unstuff -d=/home/james/oldmacfiles archive.sit If the file you unpack was protected with a password, use the -p option: unstuff -p=secret archive.sit. The text file translation filer option takes care of translating end-of-line characters from LF to CRLF and back again: unstuff -text=auto -eol=unix archive.sit.
Find more information about the Expander on its man page (type man unstuff to display it).
Aladdin Expander for Linux is available from the Aladdin Systems Web site. There are no fees for using or downloading it, but you must register with Aladdin Systems. There are two versions of the Expander, one for RPM-based systems (Red Hat, Mandrake, SuSE, and others), and the other for .deb-based systems (Debian, Corel, and others). There are no Slackware-specific packages, but it should not be difficult to convert the RPM package to work on Slackware.
Aladdin Systems: http://www.aladdinsys.com
Linux distro page: http://www.linux.org/dist/index.html
macutil package: http://www.linux.org/dist/index.html
Aladdin Expander for Linux: http://my.smithmicro.com/downloads/files/stuffit520.611linux-i386.tar.gz
Source: IBM – Linux file compression tool guide
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