I need to split a large (500MB) text file (a log4net exception file) into managle chunks like 100 5MB files would be fine.
I would think this should be a walk in the park for PowerShell. Any suggestions?
+10
A:
This is a somewhat easy task for PowerShell, complicated by the fact that the standard Get-Content cmdlet doesn't handle very large files too well. What I would suggest to do is use the .NET StreamReader class to read the file line by line in your PowerShell script and use the Add-Content cmdlet to write each line to a file with an ever-increasing index in the filename. Something like this:
$count = 1
$fileName = "{0}{1}.{2}" -f ($rootName, $count, $ext)
while(($line = $reader.ReadLine()) -ne null)
{
Add-Content -path $fileName -value $line
if((Get-ChildItem -path $fileName).Length -ge $upperBound)
{
++$count
$fileName = "{0}{1}.{2}" -f ($rootName, $count, $ext)
}
}
$reader.Close()
Lee
2009-06-16 17:00:47
This is exactly what I was looking for, and thanks for confirming my hunch that get-content is not great with large files.
Ralph Shillington
2009-06-16 19:53:25
Helpful tip: You can express numbers like this ... $upperBound = 5MB
Lee
2009-06-16 20:02:01
+2
A:
I often need to do the same thing. The trick is getting the header repeated into each of the split chunks. I wrote the following cmdlet (PowerShell v2 CTP 3) and it does the trick.
##############################################################################
#.SYNOPSIS
# Breaks a text file into multiple text files in a destination, where each
# file contains a maximum number of lines.
#
#.DESCRIPTION
# When working with files that have a header, it is often desirable to have
# the header information repeated in all of the split files. Split-File
# supports this functionality with the -rc (RepeatCount) parameter.
#
#.PARAMETER Path
# Specifies the path to an item. Wildcards are permitted.
#
#.PARAMETER LiteralPath
# Specifies the path to an item. Unlike Path, the value of LiteralPath is
# used exactly as it is typed. No characters are interpreted as wildcards.
# If the path includes escape characters, enclose it in single quotation marks.
# Single quotation marks tell Windows PowerShell not to interpret any
# characters as escape sequences.
#
#.PARAMETER Destination
# (Or -d) The location in which to place the chunked output files.
#
#.PARAMETER Count
# (Or -c) The maximum number of lines in each file.
#
#.PARAMETER RepeatCount
# (Or -rc) Specifies the number of "header" lines from the input file that will
# be repeated in each output file. Typically this is 0 or 1 but it can be any
# number of lines.
#
#.EXAMPLE
# Split-File bigfile.csv 3000 -rc 1
#
#.LINK
# Out-TempFile
##############################################################################
function Split-File {
[CmdletBinding(DefaultParameterSetName='Path')]
param(
[Parameter(ParameterSetName='Path', Position=1, Mandatory=$true, ValueFromPipeline=$true, ValueFromPipelineByPropertyName=$true)]
[String[]]$Path,
[Alias("PSPath")]
[Parameter(ParameterSetName='LiteralPath', Mandatory=$true, ValueFromPipelineByPropertyName=$true)]
[String[]]$LiteralPath,
[Alias('c')]
[Parameter(Position=2,Mandatory=$true)]
[Int32]$Count,
[Alias('d')]
[Parameter(Position=3)]
[String]$Destination='.',
[Alias('rc')]
[Parameter()]
[Int32]$RepeatCount
)
process {
# yeah! the cmdlet supports wildcards
if ($LiteralPath) { $ResolveArgs = @{LiteralPath=$LiteralPath} }
elseif ($Path) { $ResolveArgs = @{Path=$Path} }
Resolve-Path @ResolveArgs | %{
$InputName = [IO.Path]::GetFileNameWithoutExtension($_)
$InputExt = [IO.Path]::GetExtension($_)
if ($RepeatCount) { $Header = Get-Content $_ -TotalCount:$RepeatCount }
# get the input file in manageable chunks
$Part = 1
Get-Content $_ -ReadCount:$Count | %{
# make an output filename with a suffix
$OutputFile = Join-Path $Destination ('{0}-{1:0000}{2}' -f ($InputName,$Part,$InputExt))
# In the first iteration the header will be
# copied to the output file as usual
# on subsequent iterations we have to do it
if ($RepeatCount -and $Part -gt 1) {
Set-Content $OutputFile $Header
}
# write this chunk to the output file
Write-Host "Writing $OutputFile"
Add-Content $OutputFile $_
$Part += 1
}
}
}
}
Josh Einstein
2009-06-16 20:47:23
+1
A:
I've made a little modification to split files based on size of each part.
##############################################################################
#.SYNOPSIS
# Breaks a text file into multiple text files in a destination, where each
# file contains a maximum number of lines.
#
#.DESCRIPTION
# When working with files that have a header, it is often desirable to have
# the header information repeated in all of the split files. Split-File
# supports this functionality with the -rc (RepeatCount) parameter.
#
#.PARAMETER Path
# Specifies the path to an item. Wildcards are permitted.
#
#.PARAMETER LiteralPath
# Specifies the path to an item. Unlike Path, the value of LiteralPath is
# used exactly as it is typed. No characters are interpreted as wildcards.
# If the path includes escape characters, enclose it in single quotation marks.
# Single quotation marks tell Windows PowerShell not to interpret any
# characters as escape sequences.
#
#.PARAMETER Destination
# (Or -d) The location in which to place the chunked output files.
#
#.PARAMETER Size
# (Or -s) The maximum size of each file. Size must be expressed in MB.
#
#.PARAMETER RepeatCount
# (Or -rc) Specifies the number of "header" lines from the input file that will
# be repeated in each output file. Typically this is 0 or 1 but it can be any
# number of lines.
#
#.EXAMPLE
# Split-File bigfile.csv -s 20 -rc 1
#
#.LINK
# Out-TempFile
##############################################################################
function Split-File {
[CmdletBinding(DefaultParameterSetName='Path')]
param(
[Parameter(ParameterSetName='Path', Position=1, Mandatory=$true, ValueFromPipeline=$true, ValueFromPipelineByPropertyName=$true)]
[String[]]$Path,
[Alias("PSPath")]
[Parameter(ParameterSetName='LiteralPath', Mandatory=$true, ValueFromPipelineByPropertyName=$true)]
[String[]]$LiteralPath,
[Alias('s')]
[Parameter(Position=2,Mandatory=$true)]
[Int32]$Size,
[Alias('d')]
[Parameter(Position=3)]
[String]$Destination='.',
[Alias('rc')]
[Parameter()]
[Int32]$RepeatCount
)
process {
# yeah! the cmdlet supports wildcards
if ($LiteralPath) { $ResolveArgs = @{LiteralPath=$LiteralPath} }
elseif ($Path) { $ResolveArgs = @{Path=$Path} }
Resolve-Path @ResolveArgs | %{
$InputName = [IO.Path]::GetFileNameWithoutExtension($_)
$InputExt = [IO.Path]::GetExtension($_)
if ($RepeatCount) { $Header = Get-Content $_ -TotalCount:$RepeatCount }
Resolve-Path @ResolveArgs | %{
$InputName = [IO.Path]::GetFileNameWithoutExtension($_)
$InputExt = [IO.Path]::GetExtension($_)
if ($RepeatCount) { $Header = Get-Content $_ -TotalCount:$RepeatCount }
# get the input file in manageable chunks
$Part = 1
$buffer = ""
Get-Content $_ -ReadCount:1 | %{
# make an output filename with a suffix
$OutputFile = Join-Path $Destination ('{0}-{1:0000}{2}' -f ($InputName,$Part,$InputExt))
# In the first iteration the header will be
# copied to the output file as usual
# on subsequent iterations we have to do it
if ($RepeatCount -and $Part -gt 1) {
Set-Content $OutputFile $Header
}
# test buffer size and dump data only if buffer is greater than size
if ($buffer.length -gt ($Size * 1MB)) {
# write this chunk to the output file
Write-Host "Writing $OutputFile"
Add-Content $OutputFile $buffer
$Part += 1
$buffer = ""
} else {
$buffer += $_ + "`r"
}
}
}
}
}
}
+2
A:
I found this question while trying to split multiple contacts in a single vCard VCF file to separate files. Here's what I did based on Lee's code. I had to look up how to create a new StreamReader object and changed null to $null.
$reader = new-object System.IO.StreamReader("C:\Contacts.vcf")
$count = 1
$filename = "C:\Contacts\{0}.vcf" -f ($count)
while(($line = $reader.ReadLine()) -ne $null)
{
Add-Content -path $fileName -value $line
if($line -eq "END:VCARD")
{
++$count
$filename = "C:\Contacts\{0}.vcf" -f ($count)
}
}
$reader.Close()