Parsing and splitting files based on the string - powershell

Question

I have a very large file (hence .ReadLines) which I need to efficiently and quickly parse and split into other files. For each line which contains a keyword I need to copy that line and append to a specific file. This is what I have so far, the script runs but the files aren't getting populated.
$filename = "C:\dev\powershell\test1.csv"
foreach ($line in [System.IO.File]::ReadLines($filename)) {
if ($line | %{$_ -match "Apple"}){Out-File -Append Apples.txt}
elseif($line | %{$_ -match "Banana"}){Out-File -Append Bananas.txt}
elseif($line | %{$_ -match "Pear"}){Out-File -Append Pears.txt}
}
Example content of the csv file:
Apple,Test1,Cross1
Apple,Test2,Cross2
Apple,Test3,Cross3
Banana,Test4,Cross4
Pear,Test5,Cross5
I want Apples.txt to contain:
Apple,Test1,Cross1
Apple,Test2,Cross2
Apple,Test3,Cross3

Answer 1

Couple of things:
Your if conditions don't need %/foreach-object - -match will do on its own:
foreach ($line in [System.IO.File]::ReadLines($filename)) {
if($line -match "Apple"){
# output to apple.txt
}
else($line -match "Banana"){
# output to banana.txt
}
# etc...
}
The files aren't getting populated because you're not actually sending any output to Out-File:
foreach ($line in [System.IO.File]::ReadLines($filename)) {
if($line -match "Apple"){
# send $line to the file
$line |Out-File apple.txt -Append
}
# etc...
}
If your files are really massive and you expect a lot of matching lines, I'd recommend using a StreamWriter for the output files - otherwise Out-File will be opening and closing the file all the time:
$OutFiles = #{
'apple' = New-Object System.IO.StreamWriter $PWD\apples.txt
'banana' = New-Object System.IO.StreamWriter $PWD\bananas.txt
'pear' = New-Object System.IO.StreamWriter $PWD\pears.txt
}
foreach ($line in [System.IO.File]::ReadLines($filename)) {
foreach($keyword in $OutFiles.Keys){
if($line -match $keyword){
$OutFiles[$keyword].WriteLine($line)
continue
}
}
}
foreach($Writer in $OutFiles.Values){
try{
$Writer.Close()
}
finally{
$Writer.Dispose()
}
}
This way you also only have to maintain the $OutFiles hashtable if you need to update the keywords for example.