CODEWITHSUNDEEP
powershell
Chris Joseph
Chris Joseph

Reputation: 19

Extract text from string to end of document

I have a file that is too large for me to open. However, I only need the last portion of this file. There is a line of text that includes this string: DATA FROM NSERCH= 249

If I can pull everything from that line to the end of the document, I should be able to open the file.

Upvotes: 1

Views: 536

Answers (2)

Bernard Vander Beken
Bernard Vander Beken

Reputation: 5056

Update: this is not a direct answer but a workaround to only search part of the file: check the last number of lines only. This can be done repeatedly by increasing the number of lines if needed.

The Get-Content -Tail <number of lines> parameter described here specifies the number of lines from the end of a file or other item. You can use it to reduce the input. This parameter was introduced in PowerShell 3.0.

Upvotes: 1

Theo
Theo

Reputation: 61068

You can use the Get-Content cmdlet for this and read lines until it finds the string you choose as starting point for this:

$filename   = 'FULL PATH TO THE TOO LARGE TO OPEN FILE'
$outputPath = 'FULL PATH TO THE OUTPUT.TXT FILE'

$saveit = $false
Get-Content -Path $filename | ForEach-Object {
    # the $_ automatic variable represents a single line of the file
    if ($saveit) { 
        Add-Content -Path $outputPath -Value $_ 
    }
    else {
        $saveit = ($_ -match 'DATA\s+FROM\s+NSERCH=\s+249')
    }
}

The code below does the exact same thing, but requires .NET 4.0 or higher, so if you are using PowerShell 3.0 or up, you can use the [System.IO.File]::ReadLines() method to speed things up:

$filename   = 'FULL PATH TO THE TOO LARGE TO OPEN FILE'
$outputPath = 'FULL PATH TO THE OUTPUT.TXT FILE'

$saveit = $false
foreach ($line in [System.IO.File]::ReadLines($filename)) {
    if ($saveit) { 
        Add-Content -Path $outputPath -Value $line 
    }
    else {
        $saveit = ($line -match 'DATA\s+FROM\s+NSERCH=\s+249')
    }
}

Another Get-Content alternative could be:

$filename   = 'FULL PATH TO THE TOO LARGE TO OPEN FILE'
$outputPath = 'FULL PATH TO THE OUTPUT.TXT FILE'

$saveit = $false
$reader = [System.IO.File]::OpenText($filename)
while (!($reader.EndOfStream)) {
    $line = $reader.ReadLine()
    if ($saveit) { 
        Add-Content -Path $outputPath -Value $line 
    }
    else {
        $saveit = ($line -match 'DATA\s+FROM\s+NSERCH=\s+249')
    }
}
$reader.Close()

Upvotes: 2

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