Redirection Operators (>, >>)

Description

Redirection operators in PowerShell control where the output of a command goes and where its input comes from. They allow you to divert the standard output stream (what you see on the screen) to a file.

While several redirection operators exist, the most commonly used by far are > and >> for redirecting output to files.

Output Redirection: > (Overwrite)

The > operator takes the output of a command and writes it to a specified file.

Behavior:

• If the file does not exist, it will be created.
• If the file does exist, its contents will be completely overwritten with the new output. No warning is given.

Usage

This is often used to save the results of a command for later inspection.

# Get a list of all services and save it to services.txt
# If services.txt already exists, it will be replaced.
Get-Service > services.txt

Append Redirection: >> (Append)

The >> operator also sends a command's output to a file, but it adds the new output to the end of the file instead of overwriting it.

Behavior:

• If the file does not exist, it will be created.
• If the file does exist, the new output will be appended to the end of the existing content.

Usage

This is ideal for creating log files or adding new information to a file over time.

# Add a timestamped entry to the end of a log file
"User logged off at $(Get-Date)" >> activity.log

Relationship to Out-File

The > and >> operators are essentially convenient shortcuts for the Out-File cmdlet.

• > is like piping to Out-File.
• >> is like piping to Out-File -Append.

Using the Out-File cmdlet directly can be useful if you need more control, such as specifying the file encoding.

# This is the cmdlet equivalent of 'Get-Process > processes.txt'
Get-Process | Out-File -FilePath processes.txt

# This is the cmdlet equivalent of '... >> activity.log'
"User action" | Out-File -FilePath activity.log -Append

A Note on Input Redirection (<)

In shells like Bash, the < operator is commonly used to take input from a file. In PowerShell, this is very rarely used.

The idiomatic PowerShell way to get content from a file is to use the Get-Content cmdlet, which reads the file and streams its content as objects into the pipeline. This is more flexible and consistent with the rest of the PowerShell ecosystem.

Legacy/Non-PowerShell way: some-old-program.exe < input.txt The PowerShell Way: Get-Content input.txt | some-powershell-cmdlet