Compress-Zip Cmdlet

Parameters   Output Objects   Config Settings  

The Compress-ZIP component implements a compressor for ZIP, GZIP, JAR, TAR, and ZIP SFX.

Syntax

Compress-Zip [parameters]

Remarks

The format for compression is specified by the Format parameter.

The Input parameter should be set to the list of files/folders to include in the archive. The Output parameter should be set to the name and file path of the resulting archive.

For Zip, the cmdlet uses the Deflate algorithm specified in RFC 1951 for compression, and writes output compatible with PKZip, WinZip, etc.

The gzip Format is used only to archive a single file. Accordingly, the operation of the cmdlet for this format is simpler than that of the other formats.

For Jar files, the operation of the cmdlet is similar to that of the Zip Format. .class and other files may be added into a .jar file, and then may be imported into Java code or executed by a JVM.

When compressing Tar files, the interface is identical to that of the Zip format and is the same whether gzip compression is used or not.

The ZipSFX Format implements a PKZip-compatible Zip compressor to create a self-extracting archive which will run natively on Windows platforms.

The cmdlets support pipeline input for some of their parameters. Prebuilding an object and piping it to the cmdlet is very useful, but should be used with caution to prevent security conflicts. Steps have been taken to decrease the risk of a possibly accidental pipe to the cmdlet, for instance, the Credential parameter cannot be piped to the cmdlet and must be specified manually.

# compress the contents of a folder into a zip file and password protect the file Compress-Zip -Input C:\temp\* -Output C:\tesmpzip34.zip -Password mypassword # archive the contents of a folder to a tar archive Compress-Zip -Input C:\temp\* -Output C:\temptar.tar -Format tar # create a gzipped tar of a specific file Compress-Zip -Input C:\temptar.tar -Output C:\temptar.tar.gz -Format gzip

Parameter List

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The following is the full list of the parameters of the cmdlet with short descriptions. Click on the links for further details.

LogFile	The location of a file to which debug information is written.
BannerText	Optional banner text to show before the self-extraction starts.
CompressionLevel	The compression level.
Config	Specifies one or more configuration settings.
EncryptionAlgorithm	The algorithm used to encrypt files written to the archive.
FileCompressedName	Specifies the path and filename of the file in the archive.
Format	The format of the compression used.
Input	The files to be included in the archive.
LogFile	The location of a file to which debug information is written.
Output	The archive file.
Overwrite	Whether or not to overwrite the archive.
Password	The password for the zip archive.
Recurse	Whether or not to recurse into subdirectories.
ZipComment	The archive comment.

Output Objects

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The following is the full list of the output objects returned by the cmdlet with short descriptions. Click on the links for further details.

ZipFile	Returned after creation of a zip file.

Config Settings

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The following is a list of config settings for the cmdlet with short descriptions. Click on the links for further details.

BuildInfo	Information about the product's build.
CodePage	The system code page used for Unicode to Multibyte translations.
LicenseInfo	Information about the current license.
MaskSensitive	Whether sensitive data is masked in log messages.
UseInternalSecurityAPI	Tells the component whether or not to use the system security libraries or an internal implementation.

LogFile Parameter (Compress-Zip Cmdlet)

The location of a file to which debug information is written.

Syntax

Compress-Zip -LogFile string

Remarks

When specified, the cmdlet will log debug information to the file. If the file exists, the information will be appended.

Default Value

null

BannerText Property (Compress-Zip Cmdlet)

Optional banner text to show before the self-extraction starts.

Syntax

Compress-Zip -BannerText string

Remarks

If this property is set, a dialog box will pop up displaying the contents of this property as soon as the SFX executable is run. If this property is set to an empty string (default) no banner dialog will be displayed. This parameter is only valid if Format is set to ZipSFX.

Default Value

""

CompressionLevel Property (Compress-Zip Cmdlet)

The compression level.

Syntax

Compress-Zip -CompressionLevel int

Remarks

This parameter specifies the level of compression to be used, between 0 and 6. Higher values will cause the cmdlet to compress better; lower values will cause the cmdlet to compress faster. A value of 0 will store the file without compression.

This parameter is only applicable when Format is set to "Zip", "Jar", "GZip", or "ZipSFX".

Default Value

4

Config Property (Compress-Zip Cmdlet)

Specifies one or more configuration settings.

Syntax

Compress-Zip -Config string[]

Remarks

The Config parameter takes one or more name-value pairs that represent the name of the configuration setting and value, i.e.: -config "Name=Value"

Default Value

null

EncryptionAlgorithm Property (Compress-Zip Cmdlet)

The algorithm used to encrypt files written to the archive.

Syntax

Compress-Zip -EncryptionAlgorithm string

Remarks

The algorithm used to encrypt files written to the archive.

Note that files will only be encrypted if Password is set. By default the cmdlet will use standard zip encryption if Password is set, and will not encrypt data otherwise.

The cmdlet supports the use of AES, the Advanced Encryption Standard, as well as standard Zip encryption. The default encryption algorithm is the algorithm introduced in version 2.0 of the Zip specification, and is compatible with virtually all other zip utilities. However, this algorithm is considered weak and should not be used to protect sensitive data.

AES is a U.S. government standard cleared to protect even the most sensitive data. The file format used to create AES-encrypted files is designed to be compatible with WinZip 9.0. AES-encrypted files created by the cmdlet may or may not be compatible with other Zip utilities.

The cmdlet supports the use of AES with key lengths of 128, 192, or 256 bits. Note that even with the weakest (128-bit) keys AES is much more secure than standard Zip encryption.

If you use strong or maximum AES encryption the cmdlet will generate a unique salt value and cryptographic key for each file encrypted. If you use weak encryption the cmdlet will use the same salt for each file in the archive. If you are encrypting a large number of files this will have a substantial effect on performance. Set the AESGenerateUniqueKeys configuration setting to configure the salt generation independent of the key length.

If using AES encryption it is important to choose a good Password. For 128-bit keys it is recommended that your password be 32 characters long, and for 256-bit keys, 64 characters.

Important: Note that AES encryption only encrypts the contents of encrypted files within the Zip archive; it does not prevent an attacker from reading the names of files in the archive, or from adding or deleting files to or from the archive. To prevent this consider first storing your files in an unencrypted zip file, and then storing this zip file in another, AES-encrypted zip file.

Possible values:

• Default
• Weak
• Strong
• Maximum

Default Value

0

Parameter Alias

Algorithm

FileCompressedName Property (Compress-Zip Cmdlet)

Specifies the path and filename of the file in the archive.

Syntax

Compress-Zip -FileCompressedName string

Remarks

This parameter is optional and may be set to specify the path and name of the file as it exists in the archive. By default the cmdlet will automatically determine this value. If path information is specified it must be specified in a Unix style format. For instance "myfolder/myfile.txt".

This parameter is only applicable when adding a single file to the archive. If multiple files are added this parameter is ignored.

Default Value

""

Format Property (Compress-Zip Cmdlet)

The format of the compression used.

Syntax

Compress-Zip -Format string

Remarks

Possible values for the compression used include: Zip, Gzip, Jar, Tar, ZipSFX.

Default Value

0

Input Property (Compress-Zip Cmdlet)

The files to be included in the archive.

Syntax

Compress-Zip -Input string[]

Remarks

The parameter can contain directory paths as well, where everything in the directory needs to be included in the compressed file.

Default Value

null

Parameter Position

0

Parameter Alias

files

This is a required parameter.

LogFile Property (Compress-Zip Cmdlet)

The location of a file to which debug information is written.

Syntax

Compress-Zip -LogFile string

Remarks

When specified, the cmdlet will log debug information to the file. If the file exists, the information will be appended.

Default Value

""

Output Property (Compress-Zip Cmdlet)

The archive file.

Syntax

Compress-Zip -Output string

Remarks

Specifies the name of compressed file to be created.

Default Value

""

Parameter Position

1

Parameter Alias

out

Overwrite Property (Compress-Zip Cmdlet)

Whether or not to overwrite the archive.

Syntax

Compress-Zip -Overwrite SwitchParameter

Remarks

If this flag is set, the user is not queried for overwrite confirmation when the file exists.

Default Value

false

Password Property (Compress-Zip Cmdlet)

The password for the zip archive.

Syntax

Compress-Zip -Password string

Remarks

EncryptionAlgorithm allows for modification to the security algorithm used together with Password for the compressed file.

Default Value

""

Recurse Property (Compress-Zip Cmdlet)

Whether or not to recurse into subdirectories.

Syntax

Compress-Zip -Recurse SwitchParameter

Remarks

If Input includes directory paths, this setting indicates whether a recursive search for files should be done by the cmdlet.

Default Value

false

ZipComment Property (Compress-Zip Cmdlet)

The archive comment.

Syntax

Compress-Zip -ZipComment string

Remarks

This parameter specifies a global comment for the zip file. Set this parameter to include a comment in the zip file.

This parameter is only applicable when Format is set to "Zip", "Jar", or "ZipSFX".

Default Value

""

ZipFile Output Object (Compress-Zip Cmdlet)

Returned after creation of a zip file.

Syntax

Object ZipFile {
   string File;
   long Size;
   bool Secure;
}

Remarks

After constructing a zip file successfully, the ZipFile object is returned.

File contains the full path of the compressed file.

Size contains the file size of the compressed file.

Secure indicates whether or not the file was password protected.

Config Settings (Compress-Zip Cmdlet)

The cmdlet accepts one or more of the following configuration settings. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the cmdlet, access to these internal properties is provided through the Config method.

Base Config Settings