unzipsfx - self-extracting stub for prepending to ZIP archives
<name of unzipsfx+archive combo> [-cfptuz[ajnoqsCLV$]] [file(s) ... [-x xfile(s) ...]]
unzipsfx is a modified version of unzip(1) designed to be prepended to existing ZIP ar-
chives in order to form self-extracting archives. Instead of taking its first non-flag
argument to be the zipfile(s) to be extracted, unzipsfx seeks itself under the name by
which it was invoked and tests or extracts the contents of the appended archive. Because
the executable stub adds bulk to the archive (the whole purpose of which is to be as small
as possible), a number of the less-vital capabilities in regular unzip have been removed.
Among these are the usage (or help) screen, the listing and diagnostic functions (-l and
-v), the ability to decompress older compression formats (the ``reduce,'' ``shrink'' and
``implode'' methods). The ability to extract to a directory other than the current one
can be selected as a compile-time option, which is now enabled by default since UnZipSFX
version 5.5. Similarly, decryption is supported as a compile-time option but should be
avoided unless the attached archive contains encrypted files. Starting with release 5.5,
another compile-time option adds a simple ``run command after extraction'' feature. This
feature is currently incompatible with the ``extract to different directory'' feature and
remains disabled by default.
Note that self-extracting archives made with unzipsfx are no more (or less) portable
across different operating systems than is the unzip executable itself. In general a
self-extracting archive made on a particular Unix system, for example, will only self-
extract under the same flavor of Unix. Regular unzip may still be used to extract the
embedded archive as with any normal zipfile, although it will generate a harmless warning
about extra bytes at the beginning of the zipfile. Despite this, however, the self-
extracting archive is technically not a valid ZIP archive, and PKUNZIP may be unable to
test or extract it. This limitation is due to the simplistic manner in which the archive
is created; the internal directory structure is not updated to reflect the extra bytes
prepended to the original zipfile.
An optional list of archive members to be processed. Regular expressions (wild-
cards) similar to those in Unix egrep(1) may be used to match multiple members.
These wildcards may contain:
* matches a sequence of 0 or more characters
? matches exactly 1 character
[...] matches any single character found inside the brackets; ranges are specified
by a beginning character, a hyphen, and an ending character. If an exclama-
tion point or a caret (`!' or `^') follows the left bracket, then the range
of characters within the brackets is complemented (that is, anything except
the characters inside the brackets is considered a match).
(Be sure to quote any character that might otherwise be interpreted or modified by
the operating system, particularly under Unix and VMS.)
An optional list of archive members to be excluded from processing. Since wildcard
characters match directory separators (`/'), this option may be used to exclude any
files that are in subdirectories. For example, ``foosfx *.[ch] -x */*'' would
extract all C source files in the main directory, but none in any subdirectories.
Without the -x option, all C source files in all directories within the zipfile
would be extracted.
If unzipsfx is compiled with SFX_EXDIR defined, the following option is also enabled:
An optional directory to which to extract files. By default, all files and subdi-
rectories are recreated in the current directory; the -d option allows extraction
in an arbitrary directory (always assuming one has permission to write to the
directory). The option and directory may be concatenated without any white space
between them, but note that this may cause normal shell behavior to be suppressed.
In particular, ``-d ~'' (tilde) is expanded by Unix C shells into the name of the
user's home directory, but ``-d~'' is treated as a literal subdirectory ``~'' of
the current directory.
unzipsfx supports the following unzip(1) options: -c and -p (extract to standard out-
put/screen), -f and -u (freshen and update existing files upon extraction), -t (test ar-
chive) and -z (print archive comment). All normal listing options (-l, -v and -Z) have
been removed, but the testing option (-t) may be used as a ``poor man's'' listing. Alter-
natively, those creating self-extracting archives may wish to include a short listing in
the zipfile comment.
See unzip(1) for a more complete description of these options.
unzipsfx currently supports all unzip(1) modifiers: -a (convert text files), -n (never
overwrite), -o (overwrite without prompting), -q (operate quietly), -C (match names case-
insensitively), -L (convert uppercase-OS names to lowercase), -j (junk paths) and -V
(retain version numbers); plus the following operating-system specific options: -X
(restore VMS owner/protection info), -s (convert spaces in filenames to underscores [DOS,
OS/2, NT]) and -$ (restore volume label [DOS, OS/2, NT, Amiga]).
(Support for regular ASCII text-conversion may be removed in future versions, since it is
simple enough for the archive's creator to ensure that text files have the appropriate
format for the local OS. EBCDIC conversion will of course continue to be supported since
the zipfile format implies ASCII storage of text files.)
See unzip(1) for a more complete description of these modifiers.
unzipsfx uses the same environment variables as unzip(1) does, although this is likely to
be an issue only for the person creating and testing the self-extracting archive. See
unzip(1) for details.
Decryption is supported exactly as in unzip(1); that is, interactively with a non-echoing
prompt for the password(s). See unzip(1) for details. Once again, note that if the ar-
chive has no encrypted files there is no reason to use a version of unzipsfx with decryp-
tion support; that only adds to the size of the archive.
When unzipsfx was compiled with CHEAP_SFX_AUTORUN defined, a simple ``command autorun''
feature is supported. You may enter a command into the Zip archive comment, using the fol-
$AUTORUN$>[command line string]
When unzipsfx recognizes the ``$AUTORUN$>'' token at the beginning of the Zip archive com-
ment, the remainder of the first line of the comment (until the first newline character)
is passed as a shell command to the operating system using the C rtl ``system'' function.
Before executing the command, unzipsfx displays the command on the console and prompts the
user for confirmation. When the user has switched off prompting by specifying the -q
option, autorun commands are never executed.
In case the archive comment contains additional lines of text, the remainder of the ar-
chive comment following the first line is displayed normally, unless quiet operation was
requested by supplying a -q option.
To create a self-extracting archive letters from a regular zipfile letters.zip and change
the new archive's permissions to be world-executable under Unix:
cat unzipsfx letters.zip > letters
chmod 755 letters
zip -A letters
To create the same archive under MS-DOS, OS/2 or NT (note the use of the /b [binary]
option to the copy command):
copy /b unzipsfx.exe+letters.zip letters.exe
zip -A letters.exe
copy unzipsfx.exe,letters.zip letters.exe
letters == "$currentdisk:[currentdir]letters.exe"
zip -A letters.exe
(The VMS append command may also be used. The second command installs the new program as
a ``foreign command'' capable of taking arguments. The third line assumes that Zip is
already installed as a foreign command.) Under AmigaDOS:
MakeSFX letters letters.zip UnZipSFX
(MakeSFX is included with the UnZip source distribution and with Amiga binary distribu-
tions. ``zip -A'' doesn't work on Amiga self-extracting archives.) To test (or list) the
newly created self-extracting archive:
To test letters quietly, printing only a summary message indicating whether the archive is
OK or not:
To extract the complete contents into the current directory, recreating all files and sub-
directories as necessary:
To extract all *.txt files (in Unix quote the `*'):
To extract everything except the *.txt files:
letters -x *.txt
To extract only the README file to standard output (the screen):
letters -c README
To print only the zipfile comment:
The principle and fundamental limitation of unzipsfx is that it is not portable across
architectures or operating systems, and therefore neither are the resulting archives. For
some architectures there is limited portability, however (e.g., between some flavors of
Another problem with the current implementation is that any archive with ``junk''
prepended to the beginning technically is no longer a zipfile (unless zip(1) is used to
adjust the zipfile offsets appropriately, as noted above). unzip(1) takes note of the
prepended bytes and ignores them since some file-transfer protocols, notably MacBinary,
are also known to prepend junk. But PKWARE's archiver suite may not be able to deal with
the modified archive unless its offsets have been adjusted.
unzipsfx has no knowledge of the user's PATH, so in general an archive must either be in
the current directory when it is invoked, or else a full or relative path must be given.
If a user attempts to extract the archive from a directory in the PATH other than the cur-
rent one, unzipsfx will print a warning to the effect, ``can't find myself.'' This is
always true under Unix and may be true in some cases under MS-DOS, depending on the com-
piler used (Microsoft C fully qualifies the program name, but other compilers may not).
Under OS/2 and NT there are operating-system calls available that provide the full path
name, so the archive may be invoked from anywhere in the user's path. The situation is
not known for AmigaDOS, Atari TOS, MacOS, etc.
As noted above, a number of the normal unzip(1) functions have been removed in order to
make unzipsfx smaller: usage and diagnostic info, listing functions and extraction to
other directories. Also, only stored and deflated files are supported. The latter limi-
tation is mainly relevant to those who create SFX archives, however.
VMS users must know how to set up self-extracting archives as foreign commands in order to
use any of unzipsfx's options. This is not necessary for simple extraction, but the com-
mand to do so then becomes, e.g., ``run letters'' (to continue the examples given above).
unzipsfx on the Amiga requires the use of a special program, MakeSFX, in order to create
working self-extracting archives; simple concatenation does not work. (For technically
oriented users, the attached archive is defined as a ``debug hunk.'') There may be com-
patibility problems between the ROM levels of older Amigas and newer ones.
All current bugs in unzip(1) exist in unzipsfx as well.
unzipsfx's exit status (error level) is identical to that of unzip(1); see the correspond-
ing man page.
funzip(1), unzip(1), zip(1), zipcloak(1), zipgrep(1), zipinfo(1), zipnote(1), zipsplit(1)
The Info-ZIP home page is currently at
Greg Roelofs was responsible for the basic modifications to UnZip necessary to create
UnZipSFX. See unzip(1) for the current list of Zip-Bugs authors, or the file CONTRIBS in
the UnZip source distribution for the full list of Info-ZIP contributors.
Info-ZIP 20 April 2009 (v6.0) UNZIPSFX(1)