unzip.1

压缩算法的源代码

The first hyphen is the normal
switch character, and the second is a minus sign, acting on the q option.
Thus the effect here is to cancel one quantum of quietness.  To cancel
both quiet flags, two (or more) minuses may be used:
.LP
.PD 0
.Y "unzip \-t\-\-q zipfile"
.Y "unzip \-\-\-qt zipfile"
.PD
.LP
(the two are equivalent).  This may seem awkward
or confusing, but it is reasonably intuitive:  just ignore the first
hyphen and go from there.  It is also consistent with the behavior of
Unix \fInice\fP(1).
.LP
As suggested by the examples above, the default variable names are UNZIP_OPTS 
for VMS (where the symbol used to install \fIunzip\fP as a foreign command
would otherwise be confused with the environment variable), and UNZIP
for all other operating systems.  For compatibility with \fIzip\fP(1L),
UNZIPOPT is also accepted (don't ask).  If both UNZIP and UNZIPOPT
are defined, however, UNZIP takes precedence.  \fIunzip\fP's diagnostic
option (\fB\-v\fP with no zipfile name) can be used to check the values
of all four possible \fIunzip\fP and \fIzipinfo\fP environment variables.
.LP
The timezone variable (TZ) should be set according to the local timezone
in order for the \fB\-f\fP and \fB\-u\fP to operate correctly.  See the
description of \fB\-f\fP above for details.  This variable may also be
necessary in order for timestamps on extracted files to be set correctly.
.PD
.\" =========================================================================
.SH DECRYPTION
Encrypted archives are fully supported by Info-ZIP software, but due to
United States export restrictions, the encryption and decryption sources
are not packaged with the regular \fIunzip\fP and \fIzip\fP distributions.
Since the crypt sources were written by Europeans, however, they are 
freely available at sites throughout the world; see the file ``Where'' in 
any Info-ZIP source or binary distribution for locations both inside and
outside the US.
.LP
Because of the separate distribution, not all compiled versions of \fIunzip\fP
support decryption.  To check a version for crypt support, either attempt to
test or extract an encrypted archive, or else check \fIunzip\fP's diagnostic
screen (see the \fB\-v\fP option above) for ``\fC[decryption]\fR'' as one of
the special compilation options.
.LP
There are no runtime options for decryption; if a zipfile member is encrypted,
\fIunzip\fP will prompt for the password without echoing what is typed.
\fIunzip\fP continues to use the same password as long as it appears to be
valid; it does this by testing a 12-byte header.  The correct password will
always check out against the header, but there is a 1-in-256 chance that an
incorrect password will as well.  (This is a security feature of the PKWARE
zipfile format; it helps prevent brute-force attacks which might otherwise
gain a large speed advantage by testing only the header.)  In the case that
an incorrect password is 
given but it passes the header test anyway, either an incorrect CRC will be 
generated for the extracted data or else \fIunzip\fP will fail during the 
extraction because the ``decrypted'' bytes do not constitute a valid 
compressed data stream.
.LP
If the first password fails the header check on some file, \fIunzip\fP will
prompt for another password, and so on until all files are extracted.  If
a password is not known, entering a null password (that is, just a carriage
return) is taken as a signal to skip all further prompting.  Only unencrypted
files in the archive(s) will thereafter be extracted.  (Actually that's not
quite true; older versions of \fIzip\fP(1L) and \fIzipcloak\fP(1L) allowed
null passwords, so \fIunzip\fP checks each encrypted file to see if the null
password works.  This may result in ``false positives'' and extraction
errors, as noted above.)
.LP
Note that there is presently no way to avoid interactive decryption.  This
is another security feature:  plaintext passwords given on the command line 
or stored in files constitute a risk because they may be seen by others.
Future releases may (under protest, with great disapproval) support such 
shenanigans.
.PD
.\" =========================================================================
.SH EXAMPLES
To use \fIunzip\fP to extract all members of the archive \fIletters.zip\fP
into the current directory and subdirectories below it, creating any
subdirectories as necessary:
.LP
.Y "unzip letters"
.LP
To extract all members of \fIletters.zip\fP into the current directory only:
.LP
.Y "unzip -j letters"
.LP
To test \fIletters.zip\fP, printing only a summary message indicating
whether the archive is OK or not:
.LP
.Y "unzip -tq letters"
.LP
To test \fIall\fP zipfiles in the current directory, printing only the
summaries:
.LP
.Y "unzip -tq \e*.zip"
.LP
(The backslash before the asterisk is only required if the shell expands
wildcards, as in Unix; double quotes could have been used instead, as in
the source examples below.)\ \ To extract to standard output all members of 
\fIletters.zip\fP whose names end in \fI.tex\fP, auto-converting to the 
local end-of-line convention and piping the output into \fImore\fP(1):
.LP
.Y "unzip \-ca letters \e*.tex | more"
.LP
To extract the binary file \fIpaper1.dvi\fP to standard output and pipe it 
to a printing program:
.LP
.Y "unzip \-p articles paper1.dvi | dvips"
.LP
To extract all FORTRAN and C source files--*.f, *.c, *.h, and Makefile--into
the /tmp directory:
.LP
.Y "unzip source.zip ""*.[fch]"" Makefile -d /tmp"
.LP
(the double quotes are necessary only in Unix and only if globbing is turned
on).  To extract all FORTRAN and C source files, regardless of case (e.g.,
both *.c and *.C, and any makefile, Makefile, MAKEFILE or similar):
.LP
.Y "unzip \-C source.zip ""*.[fch]"" makefile -d /tmp"
.LP
To extract any such files but convert any uppercase MS-DOS or VMS names to
lowercase and convert the line-endings of all of the files to the local
standard (without respect to any files which might be marked ``binary''):
.LP
.Y "unzip \-aaCL source.zip ""*.[fch]"" makefile -d /tmp"
.LP
To extract only newer versions of the files already in the current 
directory, without querying (NOTE:  be careful of unzipping in one timezone a 
zipfile created in another--ZIP archives to date contain no timezone 
information, and a ``newer'' file from an eastern timezone may, in fact, be
older):
.LP
.Y "unzip \-fo sources"
.LP
To extract newer versions of the files already in the current directory and
to create any files not already there (same caveat as previous example):
.LP
.Y "unzip \-uo sources"
.LP
To display a diagnostic screen showing which \fIunzip\fP and \fIzipinfo\fP
options are stored in environment variables, whether decryption support was 
compiled in, the compiler with which \fIunzip\fP was compiled, etc.:
.LP
.Y "unzip \-v"
.LP
In the last five examples, assume that UNZIP or UNZIP_OPTS is set to -q.
To do a singly quiet listing:
.LP
.Y "unzip \-l file.zip"
.LP
To do a doubly quiet listing:
.LP
.Y "unzip \-ql file.zip"
.LP
(Note that the ``\fC.zip\fR'' is generally not necessary.)  To do a standard
listing:
.LP
.PD 0
.Y "unzip \-\-ql file.zip"
.LP
or
.Y "unzip \-l\-q file.zip"
.LP
or
.Y "unzip \-l\-\-q file.zip\t\fR(extra minuses don't hurt)"
.PD
.\" =========================================================================
.SH TIPS
The current maintainer, being a lazy sort, finds it very useful to define
a pair of aliases:  \fCtt\fP for ``\fCunzip \-tq\fR'' and \fCii\fP for 
``\fCunzip \-Z\fR'' (or ``\fCzipinfo\fR'').  One may then simply type 
``\fCtt zipfile\fR'' to test an archive, something which is worth making a 
habit of doing.  With luck \fIunzip\fP will report ``\fCNo errors detected 
in zipfile.zip\fP,'' after which one may breathe a sigh of relief.
.LP
The maintainer also finds it useful to set the UNZIP environment variable
to ``\fC\-aL\fR'' and is tempted to add ``\fC\-C\fR'' as well.  His ZIPINFO 
variable is set to ``\fC\-z\fR''.
.PD
.\" =========================================================================
.SH DIAGNOSTICS
The exit status (or error level) approximates the exit codes defined by PKWARE 
and takes on the following values, except under VMS:
.RS
.IP 0
normal; no errors or warnings detected.
.IP 1
one or more warning errors were encountered, but processing completed
successfully anyway.  This includes zipfiles where one or more files
was skipped due to unsupported compression method or encryption with an
unknown password.
.IP 2
a generic error in the zipfile format was detected.  Processing may have
completed successfully anyway; some broken zipfiles created by other
archivers have simple work-arounds.
.IP 3
a severe error in the zipfile format was detected.  Processing probably
failed immediately.
.IP 4-8
\fIunzip\fP was unable to allocate memory for one or more buffers.
.IP 9
the specified zipfiles were not found.
.IP 10
invalid options were specified on the command line.
.IP 11
no matching files were found.
.IP 50
the disk is (or was) full during extraction.
.IP 51
the end of the ZIP archive was encountered prematurely.
.RE
.LP
VMS interprets standard Unix (or PC) return values as other, scarier-looking
things, so by default \fIunzip\fP always returns 0 (which reportedly gets
converted into a VMS status of 1--i.e., success).  There are two compilation
options available to modify or expand upon this behavior:  defining
RETURN_CODES results in a human-readable explanation of what the real
error status was (but still with a faked ``success'' exit value), while
defining RETURN_SEVERITY causes \fIunzip\fP to exit with a ``real'' VMS
status.  The latter behavior will become the default in future
versions unless it is found to conflict with officially defined VMS codes.
The current mapping is as follows:   1 (success) for normal exit, 0x7fff0001
for warning errors, and (0x7fff000? + 16*normal_unzip_exit_status) for all
other errors, where the `?' is 2 (error) for \fIunzip\fP values 2 and 9-11,
and 4 (fatal error) for the remaining ones (3-8, 50, 51).  Check the 
``\fCunzip \-v\fR'' output to see whether RETURN_SEVERITY was defined at 
compilation time.
.PD
.\" =========================================================================
.SH BUGS
When attempting to extract a corrupted archive, \fIunzip\fP may go into
an infinite loop and, if not stopped quickly enough, fill all available disk
space.  Compiling with CHECK_EOF should fix this problem for all zipfiles,
but the option was introduced too late in the testing process to be made
the default behavior.  Future versions will be robust enough to fail
gracefully on damaged archives.  Check the ``\fCunzip \-v\fR'' output to
see whether CHECK_EOF was defined during compilation.
.LP
[MS-DOS] When extracting or testing files from an archive on a defective
floppy diskette, if the ``Fail'' option is chosen from DOS's ``Abort, Retry,
Fail?'' message, \fIunzip\fP may hang the system, requiring a reboot.  Instead,
press control-C (or control-Break) to terminate \fIunzip\fP.
.LP
Under DEC Ultrix, \fIunzip\fP will sometimes fail on long zipfiles (bad CRC,
not always reproducible).  This is apparently due either to a hardware bug
(cache memory) or an operating system bug (improper handling of page faults?).
.LP
Dates and times of stored directories are not restored.
.LP
[OS/2] Extended attributes for existing directories are never updated.  This
is a limitation of the operating system; \fIunzip\fP has no way to determine
whether the stored attributes are newer or older than the existing ones.
.LP
[VMS] When extracting to another directory, only the \fI[.foo]\fP syntax is
accepted for the \fB\-d\fP option; the simple Unix \fIfoo\fP syntax is
silently ignored (as is the less common VMS \fIfoo.dir\fP syntax).
.LP
[VMS] When the file being extracted already exists, \fIunzip\fP's query only
allows skipping, overwriting or renaming; there should additionally be a 
choice for creating a new version of the file.  In fact, the ``overwrite''
choice does create a new version; the old version is not overwritten or
deleted.
.PD
.\" =========================================================================
.SH SEE ALSO
\fIfunzip\fP(1L), \fIzip\fP(1L), \fIzipcloak\fP(1L), \fIzipgrep\fP(1L),
\fIzipinfo\fP(1L), \fIzipnote\fP(1L), \fIzipsplit\fP(1L)
.PD
.\" =========================================================================
.SH AUTHORS
The primary Info-ZIP authors (current zip-bugs workgroup) are:  Jean-loup
Gailly (Zip); Greg R. Roelofs (UnZip); Mark Adler (decompression, fUnZip); 
Kai Uwe Rommel (OS/2); Igor Mandrichenko and Hunter Goatley (VMS); John Bush
and Paul Kienitz (Amiga); Antoine Verheijen (Macintosh); Chris Herborth 
(Atari); Henry Gessau (NT); Karl Davis, Sergio Monesi and Evan Shattock 
(Acorn Archimedes); and Robert Heath (Windows).  The author of the original 
unzip code upon which Info-ZIP's is based was Samuel H. Smith; Carl Mascott 
did the first Unix port; and David P. Kirschbaum organized and led Info-ZIP
in its early days.  The full list of contributors to UnZip has grown quite
large; please refer to the CONTRIBS file in the UnZip source distribution
for a relatively complete version.
.PD
.\" =========================================================================
.SH VERSIONS
.ta \w'vx.xxnn'u +\w'fall 1989'u+3n
.PD 0
.IP "v1.2\t15 Mar 89" \w'\t\t'u
Samuel H. Smith
.IP "v2.0\t\ 9 Sep 89"
Samuel H. Smith
.IP "v2.x\tfall 1989"
many Usenet contributors
.IP "v3.0\t\ 1 May 90"
Info-ZIP (DPK, consolidator)
.IP "v3.1\t15 Aug 90"
Info-ZIP (DPK, consolidator)
.IP "v4.0\t\ 1 Dec 90"
Info-ZIP (GRR, maintainer)
.IP "v4.1\t12 May 91"
Info-ZIP
.IP "v4.2\t20 Mar 92"
Info-ZIP (zip-bugs subgroup, GRR)
.IP "v5.0\t21 Aug 92"
Info-ZIP (zip-bugs subgroup, GRR)
.IP "v5.01\t15 Jan 93"
Info-ZIP (zip-bugs subgroup, GRR)
.IP "v5.1\t\ 7 Feb 94"
Info-ZIP (zip-bugs subgroup, GRR)
.IP "v5.11\t\ 2 Aug 94"
Info-ZIP (zip-bugs subgroup, GRR)
.IP "v5.12\t28 Aug 94"
Info-ZIP (zip-bugs subgroup, GRR)
.PD