Windows

Problem

You want to search for text in a file and replace that text with something new.

Solution

To search and replace text in a file, first store the content of the file in a variable, and then store the replaced text back in that file as shown in Example 74.

Example 74. Replacing text in a file

Problem

You want to create a file for temporary purposes and want to be sure that the file does not already exist.

Solution

Use the [System.IO.Path]::GetTempFilename() method from the .NET Framework to create a temporary file:

$filename = [System.IO.Path]::GetTempFileName() (... use the file ...) RemoveItem Force $filename

Discussion

It is common to want to create a file for temporary purposes.

Problem

You want to work with binary data in a file.

Solution

Two main techniques are used when working with binary data in a file. The first is to read the file using the Byte encoding, so that PowerShell does not treat the content as text. The second is to use the BitConverter class to translate these bytes back and forth into numbers that you more commonly care about.

Problem

You want to parse and analyze a textbased logfile using PowerShell’s standard object management commands.

Solution

Use the ConvertTextObject script to work with textbased logfiles. With your assistance, it con verts steams of text into streams of objects, which you can then easily work with using PowerShell’s standard commands.

The ConvertTextObject script primarily takes two arguments:

Problem

You want to find a string or regular expression in a file.

Solution

To search a file for an exact (but case insensitive) match, use the –Simple parameter of the SelectString cmdlet:

PS >SelectString –Simple SearchText file.txt To search a file for a regular expression, provide that pattern to the SelectString cmdlet:

PS >SelectString "\(...\) ......." phone.txt To Recursively search all *.txt files for a regular expression, pipe the results of GetChildItem to the SelectString cmdlet:

Problem

You want to get the content of a file.

Solution

Provide the filename as an argument to the GetContent cmdlet:

PS >$content = GetContent c:\temp\file.txt Place the filename in a ${ } section to use the cmdlet GetContent variable syntax:

PS >$content = ${c:\temp\file.txt} Provide the filename as an argument to the ReadAllText() method to use the System. IO.File class from the .NET Framework:

PS >$content = [System.IO.File]::ReadAllText("c:\temp\file.txt")

Discussion

Problem

You want to convert a number to a different base.

Solution

The PowerShell scripting language allows you to enter both decimal and hexadecimal numbers directly. It does not natively support other number bases, but its support for interaction with the .NET Framework enables conversion both to and from binary, octal, decimal, and hexadecimal.

To convert a hexadecimal number into its decimal representation, prefix the number by 0x to enter the number as hexadecimal: PS >$myErrorCode = 0xFE4A PS >$myErrorCode

Problem

You want to work with the individual bits of a number, or work with a number built by combining a series of flags.

Solution

To directly enter a hexadecimal number, use the 0x prefix:

PS >$hexNumber = 0x1234

PS >$hexNumber

4660 To convert a number to its binary representation, supply a base of 2 to the [Convert]::ToString() method:

PS >[Convert]::ToString(1234, 2)

10011010010 To convert a binary number into its decimal representation, supply a base of 2 to the [Convert]::ToInt32() method:

Problem

You want to measure the numeric (minimum, maximum, sum, average) or textual (characters, words, lines) features of a list of objects.

Solution

Use the MeasureObject cmdlet to measure these statistical properties of a list. To measure the numeric features of a stream of objects, pipe those objects to the MeasureObject cmdlet: PS >1..10 | MeasureObject –Average Sum

Count : 10 Average : 5.5 Sum : 55 Maximum : Minimum : Property :

Problem

You want to use PowerShell to calculate more complex or advanced mathematical results.

Solution

PowerShell supports more advanced mathematical tasks primarily through its sup port for the System.Math class in the .NET Framework. To find the absolute value of a number, use the [Math]::Abs() method:

PS >[Math]::Abs(10.6)

10.6

To find the power (such as the square or the cube) of a number, use the [Math]:: Pow() method. In this case, finding 123 squared:

PS >[Math]::Pow(123, 2)