How to Replace Multiple Strings in a File Using PowerShell

Recently, someone asked me to write a complete PowerShell script to replace multiple strings in a file. In this tutorial, I will show you how to replace multiple strings in a file using PowerShell using different methods.

To replace multiple strings in a file using PowerShell, you can utilize the -replace operator in a chained manner. First, read the file content using Get-Content, then apply multiple -replace operations to update the desired strings, and finally, write the modified content back to the file using Set-Content. For example:

$filePath = "C:\MyFolder\file.txt"
$content = Get-Content $filePath
$content = $content -replace "OLD_STRING1", "NEW_STRING1" -replace "OLD_STRING2", "NEW_STRING2"
Set-Content -Path $filePath -Value $content

This script efficiently replaces OLD_STRING1 and OLD_STRING2 with NEW_STRING1 and NEW_STRING2 respectively.

Table of Contents

Replace Multiple Strings in a File Using PowerShell

This PowerShell script will be especially useful for system administrators and IT professionals managing Windows environments. It can be used to replace multiple strings in a file, such as configuration files, logs, or data files.

Method 1: Using the -replace Operator

The -replace operator is used to replace strings in PowerShell. You can chain multiple -replace operations together to replace multiple strings.

Let me show you an example.

Suppose you have a configuration file for a web application that needs to be updated. The file contains placeholders that need to be replaced with actual values:

ServerName: PLACEHOLDER_SERVER
DatabaseName: PLACEHOLDER_DB

You can use the following PowerShell script to replace these placeholders:

$filePath = "C:\Logs\config.txt"
$content = Get-Content $filePath

$content = $content -replace "PLACEHOLDER_SERVER", "us-west-server"
$content = $content -replace "PLACEHOLDER_DB", "us-west-db"

Set-Content -Path $filePath -Value $content

In this example, PLACEHOLDER_SERVER is replaced with us-west-server and PLACEHOLDER_DB is replaced with us-west-db.

Check out Count Occurrences of a Substring in a String in PowerShell

Method 2: Using foreach Loop for Multiple Replacements

If you have a large number of replacements to make, using a foreach loop can make your script more manageable.

Here is an example of replacing multiple strings in a file using a PowerShell foreach loop.

Consider a log file that records events with placeholder values for sensitive information:

User: PLACEHOLDER_USER logged in from IP: PLACEHOLDER_IP

You can use a dictionary to store your replacements and a foreach loop to apply them:

$filePath = "C:\MyFolder\log.txt"
$content = Get-Content $filePath

$replacements = @{
    "PLACEHOLDER_USER" = "JohnDoe"
    "PLACEHOLDER_IP" = "192.168.1.1"
}

foreach ($key in $replacements.Keys) {
    $content = $content -replace $key, $replacements[$key]
}

Set-Content -Path $filePath -Value $content

In this script, PLACEHOLDER_USER is replaced with JohnDoe and PLACEHOLDER_IP is replaced with 192.168.1.1.

Method 3: Using -creplace for Case-Insensitive Replacements

The -creplace operator performs case-insensitive replacements, which can be useful if the text you are replacing may appear in different cases.

Here is an example.

Suppose you have a data file with inconsistent state abbreviations:

NY, new york
ca, California
TX, texas

You can use -creplace to standardize the state abbreviations:

$filePath = "C:\MyFolder\data.txt"
$content = Get-Content $filePath

$content = $content -creplace "ny", "NY"
$content = $content -creplace "ca", "CA"
$content = $content -creplace "tx", "TX"

Set-Content -Path $filePath -Value $content

Once you execute the above PowerShell script, it will ensure all state abbreviations are capitalized uniformly. You can also see the output in the screenshot below:

Replace Multiple Strings in a File Using PowerShell

Check out Replace Placeholders in Strings Using PowerShell

Method 4: Using StringBuilder for Large Files

For very large files, using StringBuilder can improve performance by avoiding the overhead of repeatedly modifying strings.

Example: Updating a Large CSV File

Consider a large CSV file with outdated city names:

City,State,Population
Los Angeles,CA,4000000
new york city,NY,8500000
chicago,IL,2700000

You can use StringBuilder to efficiently replace the city names:

Add-Type -AssemblyName "System.Text"
$filePath = "C:\MyFolder\largefile.csv"
$content = [System.Text.StringBuilder]::new((Get-Content $filePath -Raw))

$content.Replace("new york city", "New York City")
$content.Replace("chicago", "Chicago")

[System.IO.File]::WriteAllText($filePath, $content.ToString())

This script updates new york city to New York City and chicago to Chicago in a more performance-efficient manner.

Conclusion

PowerShell offers several methods for replacing multiple strings in a file. I have explained each method with examples here, and I hope it helps you.