{"id":10104,"date":"2022-09-22T07:39:48","date_gmt":"2022-09-22T02:09:48","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-filtering-and-merging-many-large-csv-files-closed\/"},"modified":"2022-09-22T07:39:48","modified_gmt":"2022-09-22T02:09:48","slug":"solved-filtering-and-merging-many-large-csv-files-closed","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-filtering-and-merging-many-large-csv-files-closed\/","title":{"rendered":"[Solved] Filtering and Merging Many Large CSV Files [closed]"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-34616599\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"34616599\" data-parentid=\"34615606\" data-score=\"0\" data-position-on-page=\"1\" data-highest-scored=\"1\" data-question-has-accepted-highest-score=\"1\" itemprop=\"acceptedAnswer\" itemscope itemtype=\"https:\/\/schema.org\/Answer\">\n<div class=\"post-layout\">\n<div class=\"votecell post-layout--left\"><\/div>\n<div class=\"answercell post-layout--right\">\n<div class=\"s-prose js-post-body\" itemprop=\"text\">\n<p>From a performance point of view you probably want to avoid <code>Import-Csv<\/code>\/<code>Export-Csv<\/code> and go with a <a rel=\"nofollow noopener\" target=\"_blank\" href=\"https:\/\/msdn.microsoft.com\/en-us\/library\/system.io.streamreader.aspx\"><code>StreamReader<\/code><\/a>\/<a rel=\"nofollow noopener\" target=\"_blank\" href=\"https:\/\/msdn.microsoft.com\/en-us\/library\/system.io.streamwriter.aspx\"><code>StreamWriter<\/code><\/a> approach. Something like this:<\/p>\n<pre><code>$inputFolder=\"C:\\some\\folder\"\n$outputFile=\"C:\\path\\to\\output.csv\"\n\n$writer = New-Object IO.StreamWriter ($outputFile, $false)\n\nGet-ChildItem $inputFolder -File | Where-Object {\n  ...  # &lt;-- filtering criteria for selecting input files go here\n} | ForEach-Object {\n  $reader = New-Object IO.StreamReader ($_.FullName)\n  if (-not $headerWritten) {\n    # copy header line to output file once\n    $writer.WriteLine($reader.ReadLine())\n    $headerWritten = $true\n  } else {\n    # discard header line\n    $reader.ReadLine()\n  }\n\n  while ($reader.Peek() -ge 0) {\n    $line   = $reader.ReadLine()\n    $fields = $line -split ','\n    if (...) {  # &lt;-- filtering criteria for selecting output lines go here\n      $writer.WriteLine($line)\n    }\n  }\n\n  $reader.Close()\n  $reader.Dispose()\n}\n\n$writer.Close()\n$writer.Dispose()\n<\/code><\/pre>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\">3<\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved Filtering and Merging Many Large CSV Files [closed] <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] From a performance point of view you probably want to avoid Import-Csv\/Export-Csv and go with a StreamReader\/StreamWriter approach. Something like this: $inputFolder=&#8221;C:\\some\\folder&#8221; $outputFile=&#8221;C:\\path\\to\\output.csv&#8221; $writer = New-Object IO.StreamWriter ($outputFile, $false) Get-ChildItem $inputFolder -File | Where-Object { &#8230; # &lt;&#8211; filtering criteria for selecting input files go here } | ForEach-Object { $reader = New-Object IO.StreamReader &#8230; <a title=\"[Solved] Filtering and Merging Many Large CSV Files [closed]\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-filtering-and-merging-many-large-csv-files-closed\/\" aria-label=\"More on [Solved] Filtering and Merging Many Large CSV Files [closed]\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[483,1153],"class_list":["post-10104","post","type-post","status-publish","format-standard","hentry","category-solved","tag-csv","tag-powershell"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] Filtering and Merging Many Large CSV Files [closed] - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-filtering-and-merging-many-large-csv-files-closed\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Filtering and Merging Many Large CSV Files [closed] - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] From a performance point of view you probably want to avoid Import-Csv\/Export-Csv and go with a StreamReader\/StreamWriter approach. Something like this: $inputFolder=&quot;C:somefolder&quot; $outputFile=&quot;C:pathtooutput.csv&quot; $writer = New-Object IO.StreamWriter ($outputFile, $false) Get-ChildItem $inputFolder -File | Where-Object { ... # &lt;-- filtering criteria for selecting input files go here } | ForEach-Object { $reader = New-Object IO.StreamReader ... 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Something like this: $inputFolder=\"C:somefolder\" $outputFile=\"C:pathtooutput.csv\" $writer = New-Object IO.StreamWriter ($outputFile, $false) Get-ChildItem $inputFolder -File | Where-Object { ... # &lt;-- filtering criteria for selecting input files go here } | ForEach-Object { $reader = New-Object IO.StreamReader ... 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