select -first 1 on a large file

Question

I am trying to run the following command on a very large text file. However, it's very slow

((cat largefile.txt | select -first 1).split(",")).count()

Is an alternative fast way in powershell? It seems the command will scan the whole file no matter what.

jon Z · Accepted Answer · 2012-07-06T21:45:12.690

12

To only get the first x number of lines in a text file, use the –totalcount parameter:

((Get-Content largefile.txt -totalcount 1).split(",")).count

edited Jul 06 '12 at 21:45

answered Jul 06 '12 at 21:32

jon Z

This method loads the entire file into memory first, before taking the first line. – Ten98 Jun 24 '14 at 09:56

score 9 · Answer 2 · edited May 23 '17 at 11:44

9

It's worse than that - it will load the whole file and turn it into a string array.

Use the native .NET libraries to load just the first line:

$reader = [System.IO.File]::OpenText("largefile.txt")
$line = $reader.ReadLine()
$reader.Close()

edited May 23 '17 at 11:44

Community

answered Jul 06 '12 at 21:31

Arithmomaniac

What about the last lines or do you just have to wait for it to go all the way through? – Coops Jun 11 '14 at 07:38
This method only loads the first line into memory, making it many times quicker than Get-Content on larger files. – Ten98 Jun 24 '14 at 09:56
PowerShell 5.1 : Line 2 loads the whole file in memory – Jérémy Gamba May 05 '22 at 11:58

2 Answers2