Extracting Files - UNIX

This chapter describes the options PKZIP offers for extracting files from archives. These options give you various ways to choose what files to extract and where to extract them to and help you manage every aspect of extracting files.

Default Values for Commands and Options

Commands and options that have sub-options generally have a default value. This is the sub-option value that is used if none is explicitly specified on the command line. For example, the default behavior for the extract command is to unzip or uncompress all files in an archive. This behavior is set with the all sub-option of the extract command.

See this page for information on configuring default sub-option values for commands and options.

Extracting New and Existing Files

You don't have to extract all the files included in a .ZIP archive. You can select files to extract and exclude files you do not need now. If the directory into which you extract the files contains files that have the same name as those being extracted, you have to decide if you want to overwrite those files.

PKZIP provides several ways to choose which files to extract. You can extract:

• All files in an archive (the all sub-option)
• Files that are not in the target extract directory plus files that are more recent versions of files that are in the extract directory (the update sub-option)
• Only files that are more recent versions of—that is, have the same names as—files that are already in the extract directory (the freshen sub-option)

Extracting All Files from an Archive

extract=all

To extract all files from an archive file, type pkzipc -extract and the name of your archive file, as shown below:

pkzipc -extract test.zip

In this example, all files in the archive are extracted into the current directory.

By default, extract uses the all sub-option; you do not need to specify this sub-option unless you have changed the default for extract to some other sub-option.

The following example explicitly specifies the sub-option. This command does the same thing as the first example but also overrides any changed default setting. The override applies only to this instance of the command; it does not reset the default you have defined.

pkzipc -extract=all test.zip

Extracting Newer Versions of Existing Files and New Files

extract=update

Update extracts to the target extract directory only files that are not already in the directory or are newer versions of files that are already there. Archive files that are older versions of files already in the directory are not extracted.

pkzipc -extract=update test.zip

Extracting Only Newer Versions of Files

extract=freshen

Freshen extracts only files that are newer versions of files that already exist in the target extract directory. It does not add any files to the directory that are not already there in an earlier version.

pkzipc -extract=freshen test.zip

Extracting from an Archive Embedded in an Archive

embedded

An archive can contain other archive files. For example, a ZIP file can contain other ZIP archives, or a GZIP archive might contain a TAR archive. Such contained archives are said to be embedded in the archive that contains them.

If PKZIP encounters a lone embedded archive file in another archive whose contents PKZIP is extracting, PKZIP prompts you whether you would like to extract the contents of the embedded archive or just the archive itself. For example, if PKZIP is extracting the contents of outerarchive.zip, and outerarchive.zip contains innerarchive.zip, PKZIP asks you whether you want to extract the files in innerarchive.zip or just innerarchive.zip itself.

The embedded option can be used with extract to tell PKZIP to omit the prompt and just go ahead and extract the files contained in any lone archive file embedded in an archive of the specified type. You must specify the type of the outer, container archive for which you want to extract files from embedded archives.

For example:

pkzipc -extract -embedded=zip outerarchive.zip

In the example, if outerarchive.zip contains a single embedded archive (it may also contain non-archive files), PKZIP extracts the files from the embedded archive instead of extracting the embedded archive itself, and does not prompt.

The embedded option can be configured to operate by default. For example, the following command line configures embedded so that files are routinely extracted from single archives (such as .tar archives) embedded in .gz files:

pkzipc -config -embedded=gz

Put a hyphen in front of the embedded sub-option to tell PKZIP not to prompt or extract the contents of an embedded archive in an archive of a specified type. A command line containing a hyphenated sub-option overrides a configured setting. For example, the following command line extracts only an embedded archive, not its files:

pkzipc -extract -embedded=-gz outerarchive.gz

PKZIP extracts the contents of an embedded archive, with or without prompting, only if that archive is the only embedded archive in the outer archive file. If the outer archive file contains multiple embedded archives, the embedded archive files themselves are extracted.

Extracting Passphrase-Protected Files

To extract files from a passphrase-protected archive, use the extract command with the passphrase option.

• If you specify the passphrase option without a passphrase, PKZIP prompts for a passphrase. For example:

pkzipc -extract -passphrase test.zip

When you press ENTER, a prompt appears:

Passphrase?

Type the passphrase. The characters appear on the screen as asterisks, for security. Press ENTER. If you specified the correct passphrase, the files will be extracted to the current directory. If the passphrase you entered is incorrect, a warning message displays:

PKZIP: (W20) Warning! Incorrect passphrase for file: filename.ext

Retype your command line and when prompted enter the correct passphrase.

Passphrases are case sensitive.

• If you do not specify the passphrase option when extracting an archive that contains passphrase-protected files, PKZIP prompts you as if you had included the passphrase command.
• Type the passphrase (preceded by an equal sign) as part of your command. For example:

pkzipc -extract -passphrase=mysecret test.zip

If the passphrase is correct, PKZIP extracts the files (to the current directory, by default). If the passphrase is incorrect, PKZIP displays a warning message:

PKZIP: (W20) Warning! Incorrect passphrase for file: filename.ext

Retype your command line with the correct passphrase.

For greater security, enter passphrases at the prompt so that asterisks hide the characters you are entering. For information on using passphrases in scripts, see "Tips for Scripting PKZIP on UNIX."

Many other ZIP utilities can decrypt archives encrypted with traditional ZIP encryption. When a ZIP utility that can read strongly encrypted ZIP files is not available, use ZIP Reader.

Authenticating Digital Signatures

When you extract files from an archive or test an archive with the test command, PKZIP authenticates any digital signatures attached to the files or the archive. A digital signature, like a pen-and-ink signature, warrants that the signed item really comes from the signer and has not been changed.

Use the test command on an archive to check for a signature before extracting files. Testing tells you whether files are signed, authenticates any signatures, and gives you information about certificates used to sign files. PKZIP authenticates signatures automatically when extracting.

Use the crl option to have PKZIP check an accessible certificate revocation list (CRL) to see if a certificate used for signing has been revoked. (See "Checking for Revoked Certificates.")

Signatures can be applied to particular files and/or to the central directory of an archive (that is, to the archive itself).

The following table lists warning messages that can appear when you test or extract signed files, causing PKZIP to authenticate signatures.

Extracting Only Trusted Archives

verifysigner

With the verifysigner option, you can set PKZIP to extract an archive only if the archive is signed using one of a specified set of certificates or OpenPGP keys. If the verifysigner option is used, PKZIP will extract an archive only if these two conditions are met:

• The archive central directory is signed using a certificate specified with the option
• PKZIP can find a copy of each certificate specified with the option, containing the public key, in the local store (X.509 and OpenPGP) or a specified LDAP directory (X.509 only)

For example, the following command line extracts only if the archive is signed by John Smith, and PKZIP can find the certificate used to sign:

pkzipc -extract -verifysigner="John Smith" important.zip

You can use the option multiple times in the same command line to specify more than one acceptable, trusted signer:

pkzipc -extract -verifysigner="John Smith" -verifysigner="Jane Doe" important.zip

The command line above extracts if the archive is signed by either John Smith or Jane Doe, but certificates for both John Smith and Jane Doe must be found.

The requirement that PKZIP be able to find a copy of a signer's certificate locally (or on a directory server) ensures that the signer is the person you think he is. If PKZIP only authenticated the signature without also checking its certificate, you would know that an archive really was signed by someone named John Smith, but you would not know if this John Smith is the same John Smith whose certificate you have.

Specifying Trusted Signers

You can specify a list of trusted certificates/signers either by specifying each certificate individually on the command line or by specifying a file that contains a list.
By default, PKZIP searches for certificates for listed recipients only in the system's local certificate stores. Use the ldap option to cause PKZIP to search a specified LDAP directory in addition.

Specifying Trusted Signers Individually

You can specify a trusted signer using any of the following criteria:

Criterion	To use	For example
Common name	Specify, in quotes, the common name of the subject of the certificate (that is, the cn field in a string representation of a certificate); optionally, precede with: cn= By default, SecureZIP searches for certificates by common name unless another sub-option is used or the value appears to be an email address.	-verifysigner=cn="John Public" -verifysigner="John Public"
Keyid (OpenPGP)	Specify the KeyID of an OpenPGP key; optionally precede the KeyID with 0x	-archiveType=pgp -verifysigner=kid="XXXXXXXXXXXXXXXX" -verifysigner=0x XXXXXXXXXXXXXXXX
Email address	Specify the email address of the certificate (that is, the e field in a string representation of a certificate); optionally, precede with: e= SecureZIP automatically looks for an email address if the string contains an @ and a dot and looks like an email address. Certificate must contain an email address in order to be found by this method. Not all certificates embed an email address.	-verifysigner=e=john.public@xyz.com -verifysigner=john.public@xyz.com
LDAP filter	Specify the LDAP filter that you want to use to filter a search for certificates on an LDAP server that you are accessing with the ldap option; precede with: f= Use quotes if the filter string contains a space. Place the quotes around the entire filter string, including "f=". Include the following LDAP presence filter, as shown in the examples at right, to limit the search to LDAP entries that are certificates: (&(userCertificate=*)(…)) Use standard LDAP filter syntax after the "f=" prefix. This sub-option is for use only when the ldap option is used.	-verifysigner=f=(&(userCertificate=)(ou=Sales))* -verifysigner="f=(&(userCertificate=)(ou=Regional Sales))"*

Specifying a File That Lists Trusted Signers

PKZIP can extract a list of certificates from these kinds of files:

• An ordinary text file that lists the common name of each certificate on a line by itself

To use the verifysigner option to specify an ordinary text file list as a sub-option, prefix the file name with the listfile character (@, by default):

pkzipc -extract -verifysigner=@my_list_file.txt test.zip

• A PKCS#7 file: These kinds of files can contain one or more actual certificates. PKCS#7 files have the file name extensions .p7b and .p7c and do not contain private keys, only public ones.

To use the verifysigner option to specify one of these types of file to define a list comprising the owners of the certificates in the file, prefix the file name with a hash (#) character:

pkzipc -extract -verifysigner=#my_cert_file.p7b test.zip

The verifysigner option can be configured for use by default.

Extracting an Archive on STDIN or a Special File

Ordinarily, when you use the extract command to extract files from an archive, you extract the files from a physical archive file. For example, the following command line extracts all .txt files from the archive myfiles.zip:

pkzipc -extract myfiles.zip *.txt

PKZIP can also extract files from an archive that is not a physical file but is presented from an input source such as STDIN or a named pipe.

Some options are not supported when extracting from an archive that is not a physical file. In particular:

• Signatures (added with the sign option) on either files or the archive central directory are not processed.
• Because signatures are not processed, the verifysigner extraction option always fails. (This option requires verification that an archive was signed using a specified certificate.)
• File name encryption (cd option) is not supported.

Extracting from an Archive on STDIN

You can specify STDIN (standard input) instead of a physical file as the location or source of an archive from which to extract files. To do so, use a hyphen "-" in place of the name of an archive file. In a command line with the extract command (or the test or view command), the hyphen tells PKZIP to read the archive from STDIN. For example:

pkzipc -extract -noarchiveextension -silent=input -

or

cat file.zip | pkzipc -view -noarchiveextension -silent=input -

The noarchiveextension option is needed so that PKZIP does not take the hyphen as a file name and try to extract from a file named .zip. If the archive is not a ZIP archive, use the archivetype option to specify its type. For example, the following command line tells PKZIP that the file is a BZIP2 archive:

pkzipc -extract -archivetype=bzip2 -noarchiveextension -silent=input -

or

cat file.bz2 | pkzipc -view -archivetype=bzip2 -noarchiveextension -silent=input -

The silent option is set to the input sub-option to suppress any PKZIP requests for input (a passphrase, for example). If input is needed, the extraction fails with an error.

See "Writing an Archive to STDOUT" for a way to create an archive that is presented through STDIN.

Extracting an Archive from a Named Pipe, UNIX Domain Socket, or Device File

You can specify a named pipe, UNIX socket, or device file instead of a physical file as the location of an archive from which to extract files. The pipe, socket, or device must first be created, perhaps by another program, and an archive must be written to it. To extract, use the name of the pipe, socket, or device in the command line in place of the name of an archive file. For example:

pkzipc -extract -noarchiveextension <name of pipe or socket>

As when extracting from STDIN, you must use the noarchiveextension option to prevent PKZIP from trying to extract from a .zip file—in this case, one named for the pipe or socket.

PKZIP tries to extract from ZIP-format archives by default. To extract from a different type of archive, use the archivetype option to specify the type. For example, the following command line tells PKZIP that the archive is a BZIP2-format file:

pkzipc -extract -archivetype=bzip2 -noarchiveextension <name of pipe or socket>

You must use the full UNC path when referring to a named pipe on Windows. For example:

pkzipc -extract -noarchiveextension \\.\pipe\mypipe *.doc

In the preceding example, the dot in the path

\\.\pipe\mypipe

references the current machine. To reference a pipe on a different machine—named boulder—specify the machine.

\\boulder\pipe\mypipe

You can use either a name or an IP address to specify a machine.

You must use the noarchiveextension option to prevent PKZIP from trying to extract from an archive file named .zip.

Use the timeout option to have PKZIP wait a specified number of seconds before checking a socket or device for more data.

Extracting Data to STDOUT or Special Files

"Adding Data from STDIN or Special Files" describes how to capture data from STDIN or such special files as named pipes or UNIX sockets and add it to an archive. Files can also be extracted from an archive to STDOUT or to special files.

To extract to STDOUT, use the console command (see "Extracting Files Only for Display" later in this chapter for more on console). To extract to special files, you can use either console or extract.

Extracting to STDOUT

To extract to STDOUT, use the console command instead of extract.

By default, the console command writes a PKZIP banner of text at the beginning of the output; it also inserts a file header containing the name of the file before each file's data, like this:

==============================
 output.txt
 ==============================

To suppress the banner, use the silent option with the banner sub-option. To suppress the file header as well, append the fileheader sub-option. The command line below writes only the data from output.txt to STDOUT.

pkzipc -console -silent=banner,fileheader data.zip output.txt

Extracting to Special Files

By redirecting its output, you can also use the console command to extract data to a named pipe or UNIX socket.

The console command has the limitation that all output goes to one place: multiple files cannot be extracted to multiple destinations—different pipes, for example—using a single command line. To extract to one or more special files, use extract with the stream option instead of using console.

Extracting to Special Files on UNIX

The following command line extracts all files in an archive to a UNIX pipe or socket file named mystream:

pkzipc -console -silent=banner,fileheader data.zip > mystream

To extract archived data to a special file on UNIX, use extract with the stream option to extract to a pipe or socket file.

The following command line extracts mystream either to an existing pipe named mystream or, if no such pipe exists, to an ordinary file named mystream.

pkzipc -extract -stream data.zip mystream

If the stream option is omitted, the file is extracted as an ordinary file, and any existing mystream pipe is removed.

The following command line extracts multiple files to multiple pipes:

pkzipc -extract -stream data.zip mystream otherstream

You can use the rename option to rename the extracted files to match the names of their intended targets. For example, if data.zip contains the files myinfo and otherinfo, the following command line renames the extracted copies to mystream and otherstream to enable them to extract to pipes having those names:

pkzipc -extract -stream -rename=/info/stream/ data.zip mystream otherstream

The rename option can be used multiple times in a command line. See "Renaming Files."

Extracting to Dynamically Named Folders

substitution

With the substitution option, you can extract the contents of an archive to a folder whose name and path are constructed on the fly from tokens embedded in the specification for the destination folder on the command line. PKZIP creates the actual name of the folder by substituting values for the tokens when the archive is extracted. Tokens are supplied that enable you to name the folder after the archive to be extracted to it, replicate the path to the archive, and embed timestamp elements.

With this option, you can use a single command line to extract multiple archives each to its own custom-named folder.

The table below lists the tokens for use with the substitution option when extracting.

The following command line shows a straightforward example of the substitution option. The command line extracts all ZIP files in the current directory, each to a subdirectory named after the ZIP archive extracted there. If two ZIP files, myfiles.zip and myfiles2.zip, are in the current directory, the command line extracts them to subfolders named myfiles and myfiles2, respectively.

pkzipc -extract -substitution *.zip {archivename}\

The example below uses the {archivepath} token to specify the archive path for the destination folder. The {archivepath} token includes a leading backslash (or slash). The command line extracts all ZIP files in folder \$HOME\thomas\ each to its own subfolder in other\location\$HOME\thomas\. For example, it extracts myfiles.zip in folder \$HOME\thomas\ to subfolder other\location\$HOME\thomas\myfiles.

pkzipc -extract -substitution \$HOME\thomas\*.zip \other\location{archivepath}\{archivename}\

Most UNIX shells treat { and } and * as metacharacters, which need to be escaped for the command line to work properly. To be safe, put the whole file name or path name in quotation marks when using the substitution option on UNIX.

Formatted for UNIX, the preceding example looks like this:

pkzipc -extract -substitution "/$HOME/thomas/*.zip" "/other/location{archivepath}/{archivename}/"

If run from C:\myproject, the command line below extracts all ZIP files to C:\myproject\test. The dot in the specification for the target folder locates the start of the extraction path in the current folder. The drive letter is stripped.

pkzipc -extract -substitution D:\test\*.zip .{archivepath}

If the date is July 31, 2008, and the directory /$HOME/app1/ contains myfiles.zip and test2.zip, the command line below extracts test1.zip to folder test1-07312008 and test2.zip to folder test2-07312008:

pkzipc extract -substitution /$HOME/app1/*.zip {archivename}-{mm}{dd}{yyyy}*

The following example shows how {archivepath} strips out a share path. If //server/share/path/to/zips contains test1.zip and test2.zip, and the current directory is testme, the command line extracts test1.zip to /path/to/zips/test1 and extracts test2.zip to /path/to/zips/test2:

pkzipc -extract -substitution //server/share/path/to/zips/*.zip {archivepath}{archivename}*/

The example below uses the substitution option when extracting an archive from STDIN, represented by a hyphen in the command line (see "Extracting an Archive on STDIN or a Special File"). If the date is July 31, 2008, an archive provided on STDIN is extracted to directory -07312008. In this case, {archivepath} and {archiveext} are replaced with nothing, and {archivename} is replaced with a hyphen.

pkzipc -extract -substitution -noarchiveextension - {archivepath} {archivename}{archiveext}{mm}{dd}{yyyy}

The substitution option can also be used with the add command and a slightly different set of tokens to insert a timestamp in the name of a newly created or updated archive. See "Inserting a Timestamp in the Archive File Name."

Extracting Files in Lower Case

lowercase

The lowercase option allows you to extract files in lower case regardless of how the file name was originally archived. To force the file names to be extracted in lowercase, use the following example:

pkzipc -extract -lowercase test.zip

Changing Ownership When Extracting

id

By default, SecureZIP stores the UID and/or GID of the user who adds a file. When extracting, SecureZIP gives files the UID and GID of the user performing the extraction. The id option restores files' original ownership when extracting.

pkzipc -extract -id=jon test.zip

To use the id option, you must be either the super user or the user listed in the archive as the owner of the file.

The id option is configurable.

owner

The owner option can be used when adding or extracting files. The option changes files' associated UID and/or GID to a specified UID or GID. The following example specifies both. It sets the owner to jon and the group to eng.

pkzipc -extract -owner=jon:eng test.zip

When adding files, you can use the option to mask off your ownership information. For example, the following command line marks files as owned by the root account.

pkzipc -add -owner=0:0 test.zip

To use the owner option when extracting, you must be either the super user or the user listed in the archive as the owner of the file.

When extracting files, you can use the option to mark the files as owned by someone else.

The owner option is configurable.

Preserving File Times

times

The times option allows you to preserve the access, creation and modification times of the extracted files. Specify the sub-option all to preserve all times, use access to preserve the access times only, use modify to restore the time of last modification times or create to restore the creation times.

To preserve all the file times, use the following example:

pkzipc -extract -times=all test.zip

On UNIX systems, no creation time is preserved, as most UNIX file systems do not track when a file was created.

Retaining Directory Structure while Extracting

directories

If you stored directory path information within a .ZIP file, you can re-create those directory paths when you extract the files. For example, if you compressed a file called apples.doc in the temp/fruit directory, and you stored temp/fruit you can re-create temp/fruit in the location in which you extract the files.

To re-create directories, use the directories option with the extract command, as in the following example:

pkzipc -extract -directories test.zip

When you use this command, all directories that were stored in the .ZIP file will be retained during extraction. The directory path stored is appended to the directory in which you extract the files. For example, if your extract directory is /doc, and a directory path stored with the files is temp/fruit, the files would now be extracted to /doc/temp/fruit.

Sorting Files in the Extract Directory

sort

PKZIP allows you to specify the sort order of files that are compressed in a .ZIP file or extracted into a destination directory. For example, if you wish to extract files in a specified sort order (by date), you would type the following and press ENTER:

pkzipc -extract -sort=date test.zip

In this example, all files that exist in the test.zip file are extracted into the current directory sorted in ascending order by date. For more information on sort options, see the Command Reference page.

Extracting Files Only for Display

console

PKZIP gives you the option of displaying specific files contained in a .ZIP file to your computer monitor. For example, if you wish to view the contents of all *.txt files contained in a .ZIP file, type the following and press ENTER:

pkzipc -console test.zip *.txt

In this example, all files with a .txt extension that exist in the test.zip are displayed on the monitor. Since many .ZIP files contain an information document (such as readme.txt), the console option is a good way to determine the contents of a .ZIP file without requiring you to extract a file or file(s) to your hard drive.

You can also use the console and silent options to redirect files to pipe files directly to another program.

Extracting Files with a List File

You can use a list file to specify files to extract from an archive. In the list file, specify file and path name information to identify the target files. You can explicitly list individual files to extract, or use wild card characters (*, ?) to specify multiple files in a single entry. For example, entries like the four below are permitted:

Fred\My Documents\tmp\yparent\ychild\ychild1.txt
 Documents and Settings\Fred\My Documents\tmp\yparent*.txt
 dparent?.txt
 *.xls

How you identify files in an archive depends on the path information that was archived with them. In an archive, path information is treated as part of a file name for purposes of identification. So d*.txt does not just get all .txt files whose names start with d in the root folder of an archive; it gets all .txt files whose pathname starts with d. For example, it would get these files:

Documents and Settings\Fred\My Documents\tmp\yparent*.txt
dparent?.txt 

Do not use drive letters in a list file used to extract. Drive letters are not saved with other path information in an archive and are not allowed in extraction list file entries.

To specify a list file to use to extract, prefix the pathname of the list file with the @ character on the command line after the name of the archive. For example, the following line extracts using list file mylist.txt:

pkzipc -extract test.zip @tmp\mylist.txt

See the listfile option for information on using this option to create a list file. See the view option for information on viewing path information saved in an archive.