I don't have a decent text editor on this server, but I need to see what's causing an error on line 10 of a certain file. I do have PowerShell though...
7 Answers
It's as easy as using select:
Get-Content file.txt | Select-Object -Index (line - 1) E.g. to get line 5
Get-Content file.txt | Select-Object -Index 4 Or you can use:
(Get-Content file.txt)[4] 
3 Comments
Stacker
wouldnt this reterive the whole content into memory first which is bad ?
Frode F.
See C.B.'s answer for performance stats (time, not memory). If you're working with large files, then this is inefficient. If you're using small and just a few files, then performance isn't that important. Sometimes clean code is more important. This answer is 5 years old - things have changed in powershell as well
Hashbrown
@Stacker @Lance's answer is the correct answer (so long as the line you need is toward the start of the file). Basically equivalent to 'nix'
head -nThis will show the 10th line of myfile.txt:
get-content myfile.txt | select -first 1 -skip 9 both -first and -skip are optional parameters, and -context, or -last may be useful in similar situations.
1 Comment
lit
This will work well for small files. Unless something has changed,
Get-Content will read the entire file into memory. That does not always work well with large files.You can use the -TotalCount parameter of the Get-Content cmdlet to read the first n lines, then use Select-Object to return only the nth line:
Get-Content file.txt -TotalCount 9 | Select-Object -Last 1; Per the comment from @C.B. this should improve performance by only reading up to and including the nth line, rather than the entire file. Note that you can use the aliases -First or -Head in place of -TotalCount.
Comments
Here's a function that uses .NET's System.IO classes directly:
function GetLineAt([String] $path, [Int32] $index) { [System.IO.FileMode] $mode = [System.IO.FileMode]::Open; [System.IO.FileAccess] $access = [System.IO.FileAccess]::Read; [System.IO.FileShare] $share = [System.IO.FileShare]::Read; [Int32] $bufferSize = 16 * 1024; [System.IO.FileOptions] $options = [System.IO.FileOptions]::SequentialScan; [System.Text.Encoding] $defaultEncoding = [System.Text.Encoding]::UTF8; # FileStream(String, FileMode, FileAccess, FileShare, Int32, FileOptions) constructor # http://msdn.microsoft.com/library/d0y914c5.aspx [System.IO.FileStream] $input = New-Object ` -TypeName 'System.IO.FileStream' ` -ArgumentList ($path, $mode, $access, $share, $bufferSize, $options); # StreamReader(Stream, Encoding, Boolean, Int32) constructor # http://msdn.microsoft.com/library/ms143458.aspx [System.IO.StreamReader] $reader = New-Object ` -TypeName 'System.IO.StreamReader' ` -ArgumentList ($input, $defaultEncoding, $true, $bufferSize); [String] $line = $null; [Int32] $currentIndex = 0; try { while (($line = $reader.ReadLine()) -ne $null) { if ($currentIndex++ -eq $index) { return $line; } } } finally { # Close $reader and $input $reader.Close(); } # There are less than ($index + 1) lines in the file return $null; } GetLineAt 'file.txt' 9; Tweaking the $bufferSize variable might affect performance. A more concise version that uses default buffer sizes and doesn't provide optimization hints could look like this:
function GetLineAt([String] $path, [Int32] $index) { # StreamReader(String, Boolean) constructor # http://msdn.microsoft.com/library/9y86s1a9.aspx [System.IO.StreamReader] $reader = New-Object ` -TypeName 'System.IO.StreamReader' ` -ArgumentList ($path, $true); [String] $line = $null; [Int32] $currentIndex = 0; try { while (($line = $reader.ReadLine()) -ne $null) { if ($currentIndex++ -eq $index) { return $line; } } } finally { $reader.Close(); } # There are less than ($index + 1) lines in the file return $null; } GetLineAt 'file.txt' 9; 4 Comments
northben
Overengineering: See BACON's solution on SO for a quick way to read a text file. :)
Tao
I stumbled on this question while looking for how to do this for a large file - exactly what I needed.
Lance U. Matthews
@Tao Thank you. Glad someone found this useful. Sometimes the built-in PowerShell cmdlets don't give you the control or efficiency you need, especially, like you said, when working with large files.
prabhakaran
+1 For Northben's (funny) explanation for overengineering. +1 For Bacon for his effort.
Just for fun, here some test:
# Added this for @Graimer's request ;) (not same computer, but one with HD little more # performant...) > measure-command { Get-Content ita\ita.txt -TotalCount 260000 | Select-Object -Last 1 } Days : 0 Hours : 0 Minutes : 0 Seconds : 28 Milliseconds : 893 Ticks : 288932649 TotalDays : 0,000334412788194444 TotalHours : 0,00802590691666667 TotalMinutes : 0,481554415 TotalSeconds : 28,8932649 TotalMilliseconds : 28893,2649 > measure-command { (gc "c:\ps\ita\ita.txt")[260000] } Days : 0 Hours : 0 Minutes : 0 Seconds : 9 Milliseconds : 257 Ticks : 92572893 TotalDays : 0,000107144552083333 TotalHours : 0,00257146925 TotalMinutes : 0,154288155 TotalSeconds : 9,2572893 TotalMilliseconds : 9257,2893 > measure-command { ([System.IO.File]::ReadAllLines("c:\ps\ita\ita.txt"))[260000] } Days : 0 Hours : 0 Minutes : 0 Seconds : 0 Milliseconds : 234 Ticks : 2348059 TotalDays : 2,71766087962963E-06 TotalHours : 6,52238611111111E-05 TotalMinutes : 0,00391343166666667 TotalSeconds : 0,2348059 TotalMilliseconds : 234,8059 > measure-command {get-content .\ita\ita.txt | select -index 260000} Days : 0 Hours : 0 Minutes : 0 Seconds : 36 Milliseconds : 591 Ticks : 365912596 TotalDays : 0,000423509949074074 TotalHours : 0,0101642387777778 TotalMinutes : 0,609854326666667 TotalSeconds : 36,5912596 TotalMilliseconds : 36591,2596 the winner is : ([System.IO.File]::ReadAllLines( path ))[index]
4 Comments
Frode F.
how about @Bacon 's answer ? since you already have a sample file :-)
CB.
@Graimer Added :). All this test are intended for seeking in a big file for big index, I think that for little index's value the results may vary. Each test was done in a new powershell session to avoid HD pre-caching features.
Lance U. Matthews
I'm really surprised that
ReadAllLines() is not only faster, but so much faster than the two uses of Get-Content. As the name suggests, it's reading the entire file, too. Anyways, I posted another approach, if you want to try that one, too. Also, whenever I use Measure-Command to benchmark code I usually run it like this 1..10 | % { Measure-Command { ... } } | Measure-Object TotalMilliseconds -Average -Min -Max -Sum; so I can get a more accurate number from multiple test runs.
Nate Anderson
I get this error:
Exception calling "ReadAllLines" with "1" argument(s): "Array dimensions exceeded supported range." At line:1 char:1I know that this is an old question, but despite being one of the most viewed ones for this topic, none of the answers are completely satisfactory to me. Get-Content is easy to use, but it shows its limitations when it comes to really large text files (e.g. >5 GB).
I figured out a solution which does not require the entire file to be loaded into main memory and that is way faster than Get-Content (almost as fast as sed on Linux, like this):
[Linq.Enumerable]::ElementAt([System.IO.File]::ReadLines("<path_to_file>"), <index>) This takes about 4 seconds on my machine to find a line in the middle of a ~4.5 GB file, whereas (Get-Content -Path <path_to_file> -TotalCount <index>)[-1] takes about 35 seconds.
Comments
To reduce memory consumption and to speed up the search you may use -ReadCount option of Get-Content cmdlet (https://technet.microsoft.com/ru-ru/library/hh849787.aspx).
This may save hours when you working with large files.
Here is an example:
$n = 60699010 $src = 'hugefile.csv' $batch = 100 $timer = [Diagnostics.Stopwatch]::StartNew() $count = 0 Get-Content $src -ReadCount $batch -TotalCount $n | % { $count += $_.Length if ($count -ge $n ) { $_[($n - $count + $_.Length - 1)] } } $timer.Stop() $timer.Elapsed This prints $n'th line and elapsed time.
(get-content myfile.txt)[9]?