Read file line by line in PowerShell

问题

I want to read a file line by line in PowerShell. Specifically, I want to loop through the file, store each line in a variable in the loop, and do some processing on the line.

I know the Bash equivalent:

while read line do
    if [[ $line =~ $regex ]]; then
          # work here
    fi
done < file.txt

Not much documentation on PowerShell loops.

回答1:

Not much documentation on PowerShell loops.

Documentation on loops in PowerShell is plentiful, and you might want to check out the following help topics: about_For, about_ForEach, about_Do, about_While.

foreach($line in Get-Content .\file.txt) {
    if($line -match $regex){
        # Work here
    }
}

Another idiomatic PowerShell solution to your problem is to pipe the lines of the text file to the ForEach-Object cmdlet:

Get-Content .\file.txt | ForEach-Object {
    if($_ -match $regex){
        # Work here
    }
}

Instead of regex matching inside the loop, you could pipe the lines through Where-Object to filter just those you're interested in:

Get-Content .\file.txt | Where-Object {$_ -match $regex} | ForEach-Object {
    # Work here
}

回答2:

Get-Content has bad performance; it tries to read the file into memory all at once.

C# (.NET) file reader reads each line one by one

Best Performace

foreach($line in [System.IO.File]::ReadLines("C:\path\to\file.txt"))
{
       $line
}

Or slightly less performant

[System.IO.File]::ReadLines("C:\path\to\file.txt") | ForEach-Object {
       $_
}

The foreach statement will likely be slightly faster than ForEach-Object (see comments below for more information).

回答3:

The almighty switch works well here:

'one
two
three' > file

$regex = '^t'

switch -regex -file file { 
  $regex { "line is $_" } 
}

Output:

line is two
line is three

来源：https://stackoverflow.com/questions/33511772/read-file-line-by-line-in-powershell

标签

powershell

powershell-ise