How to Select Multiple Patterns in a String Using PowerShell

1. Introduction to the Select-String Command in Windows
2. Use Select-String Cmdlet in Windows PowerShell

PowerShell has a similar command to Linux’s grep that looks for a string pattern and displays it as output in the command line. This article discusses which cmdlet serves its function of searching for specific string patterns using Windows PowerShell.

Introduction to the Select-String Command in Windows

The grep command in Linux is comparable to the Select-String command in Windows. The cmdlet searches for the first match in each line by default and then displays the file name, line number, and text within the matched string.

The Select-String command may also work with multiple file encodings, such as Unicode text, by determining the encoding format using the byte-order-mark (BOM). Select-String will think it’s a UTF8 file if the BOM is missing.

Parameters of Select-String

• AllMatches – Usually, the Select-String command will only look for the first match in each line; however, the cmdlet will search for more than one match using this parameter. The parameter will still emit a single MatchInfo object for each line, containing all matches found.
• CaseSensitive – String matches are not case-sensitive by default. This parameter forces the cmdlet to look for matches precisely the input pattern.
• Context – A parameter that we can define the number of lines before and after the match that the parameter will display. Appending this parameter modifies the emitted MatchInfo object to include a new Context property containing the specified lines.
• Select-String to another Select-String call, the context won’t be available since we are only searching on the single resulting MatchInfo line property.
• Culture – Used with the SimpleMatch parameter, specifies a culture to be matched with the specified pattern. This parameter includes options such as en-US, es, or fr-FR examples.

The Ordinal and Invariant choices are two more useful possibilities.

• Ordinal is used for non-linguistic binary comparisons, while Invariant is used for independent culture comparisons. This parameter debuted in PowerShell 7 and was not present in previous versions.

Note that this will use the system’s current culture, which we can determine using the Get-Culture command.

• Encoding – Specifies the encoding of the target file to search, which default of utf8NoBOM. The Encoding option now takes numeric IDs of registered code pages, or string names, such as windows-1251, starting with PowerShell Core 6.2.

  1. ASCII: This parameter uses the encoding for the ASCII (7-bit) character set.
  2. bigendianunicode: This parameter encodes in UTF-16 format using the big-endian byte order.
  3. OEM: This parameter uses the default encoding for MS-DOS and console programs.
  4. Unicode: This parameter encodes in UTF-16 format using the little-endian byte order.
  5. utf7: This parameter encodes in UTF-7 format.
  6. utf8: This parameter encodes in UTF-8 format.
  7. utf8BOM: This parameter encodes in UTF-8 format with Byte Order Mark (BOM)
  8. tf8NoBOM: Encodes in UTF-8 format without Byte Order Mark (BOM)
  9. utf32: Encodes in UTF-32 format.

• Exclude – With the Path parameter, exclude specific items using a pattern, such as *.txt.

• Include – The Include parameter, like the Exclude parameter, will only include entries that match a pattern, such as *.csv.

• List – This parameter returns the first instance of matching text from each input file. This parameter is intended to be a fast and efficient way to retrieve a listing of files with matching contents.

• LiteralPath tells Select-String to use the values as input instead of interpreting values such as * as a wildcard. If the path includes escaping characters, enclose them in single quotation marks to not analyze.

• NoEmphasis – This parameter disables the highlighting of matches. The Emphasis parameter uses negative colors based on the background text colors.

• NotMatch – This parameter looks for text that does not match the specified pattern.

• Path – The path to the files to be searched is specified by this parameter. We can use wildcards, but we can’t just specify a directory.

  The local directory is the default.

• Pattern – This parameter specifies the pattern to search the input content or files based on regular expressions.

• SimpleMatch – Instead of regular expressions, this parameter utilizes a basic match. Because no regular expression is used, the Matches field of the returned MatchInfo object is empty.

• Raw – This parameter outputs the matching strings without a MatchInfo object. This behavior is most similar to grep and not PowerShell’s more object-oriented nature.

• Quiet – Only returns a Boolean value of $true or $false if the pattern is found.

Use Select-String Cmdlet in Windows PowerShell

Let’s have examples and see how we can leverage Select-String to make finding text matches easier. Starting with a straightforward example, let us look for John in a handful of CSV files.

Example Code:

Select-String -Path "PS\*.csv" -Pattern "John"

Output:

PS\user1.csv:3:John,Doe,jdoe@test.com,Male
PS\user2.csv:5:John,Johnson,jjohnson@abccompany.com,Male

We can also look at the display properties of each output.

Example Code:

Select-String -Path "Users\*.csv" -Pattern "John" | Select-Object * -First 1

Output:

IgnoreCase : True
LineNumber : 3
Line       : John,Doe,jdoe@test.com,Male
Filename   : user1.csv
Path       : C:\Temp\PS
Pattern    : John
Context    :
Matches    : {2}

If we want to search for multiple patterns, we can separate the parameter values with a comma under the Pattern parameter.

Example Code:

Select-String -Path "Users\*.csv" -Pattern "John", "Henry", "Jonathan"