PowerShell 和 CSV

Question

下午好。我希望我能够获得一些我正在编写脚本以维护 CSV 文件的 PowerShell 的帮助。这个文件最大的问题是日期格式会通过添加到文件的系统发生变化。我的目标是能够运行此脚本，让它将所有日期更改为 MM/dd/yyyy，从最旧到最新（按日期）排序，然后搜索重复的地址并保留最旧的。

我有一点点开始，但我有点卡住了。我也做了很多（我相信是）很多不必要的文件创建，并且使这些事情过于复杂。我是 PowerShell 的新手，而且一般都在编写脚本。

这是我的数据的样子（注意第一行没有引号，输出应该保持不变）。这是一个 txt 文件，但读起来像 CSV。

dev_address,date_added,comments,user_id,dev_name
"00:01:02:03:04:0a","05/19/2014","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0b","05/19/2014","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0c","05/19/2013","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0d","2015/7/8","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0e","2016/06/03","NIC Manufacturer = Microsoft","bob","comp1"

这是我目前所写的：

$devList = Import-Csv .\TestFile.txt

$a = Get-Content .\TestFile.txt -TotalCount 1

Add-Content -Path '.\foo2.txt' -Value "$a"

$countList = -1

ForEach($devList in $devList)
    {
        $devMAC = $devList.dev_address
        $devDate = $devList.date_added
        $devComm = $devList.comments
        $devUser = $devList.user_id
        $devMName = $devList.dev_name

        $devDate = ([datetime]($devDate)).ToString('MM/dd/yyyy')

        Add-Content -Path '.\foo2.txt' -Value """$devMAC"",""$devDate"",""$devComm"",""$devUser"",""$devMName"""
    }

Import-Csv '.\foo2.txt' | Sort-Object {[datetime]$_.date_added} | Export-Csv -NoTypeInformation '.\foo3.txt'

现在我知道这很混乱。所以我会尝试解释我在做什么。导入 CSV 文件。将 CSV 文件的第一行（标题）保存到一个变量中，以便我可以稍后将其原封不动地弹出到最终文件中。接下来，将每条记录的数据导入到变量中，以便将它们输入到最终文件中。我有点弄清楚日期的事情了。这似乎将日期更改为正确的格式，然后倒数第二行将其写入 $devList 中每个条目的文件。最后一行是导入第二个文件，按日期排序并导出到第三个最终文件。主要用于故障排除目的是多余的。不打算拥有 3 个文件。

导入数据的最佳方法是什么，将日期格式化为 MM/dd/yyyy，按最旧到最新排序，然后根据 dev_address 删除重复记录（但保留最旧的记录），然后导出到一个新文件，包括没有引号的 CSV 标头？

提前谢谢你:-)

编辑：

抱歉，我应该包含所需的输出。假设我有这个文件：

dev_address,date_added,comments,user_id,dev_name
"00:01:02:03:04:0a","05/19/2014","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0a","06/05/2014","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0c","04/20/2013","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0d","2015/7/8","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0e","2016/06/03","NIC Manufacturer = Microsoft","bob","comp1"

这是我想要的输出：

dev_address,date_added,comments,user_id,dev_name
"00:01:02:03:04:0c","04/20/2013","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0a","05/19/2014","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0d","07/08/2015","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0e","06/03/2016","NIC Manufacturer = Microsoft","bob","comp1"

如您所见，日期已固定且已排序，已删除多余的 dev_address 并保留了最早的日期。顶线保持不变。

Answer 1

我认为这就是你要找的东西。你自己非常接近。 :) 您的最终输出将在output.txt。

顶行（标题）用双引号括起来。请考虑坚持这一点，因为它将在不同的 cmdlet 和/或其他进程之间创建通用的“csv”格式，以便它们将 CSV 文件识别为通用的。

编辑：我之前按错误的顺序进行了排序，我已对其进行了调整：

$devices = Import-CSV 38488676.csv

foreach ($device in $devices)
{
    $date = $device.date_added -as [DateTime];
    $device.date_added = $date.ToString("M/d/yyyy")
    #this foreach could all be done in one line by itself...
    #but it's easier to visualize and understand when broken out more
}

$devices | Sort-Object {$_.date_added -as [datetime]} | Sort dev_address -Unique | Export-CSV -NoTypeInformation output.txt

这给了我以下输出：

"dev_address","date_added","comments","user_id","dev_name"
"00:01:02:03:04:0c","4/20/2013","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0a","6/5/2014","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0d","7/8/2015","NIC Manufacturer = Microsoft","bob","comp1"
"00:01:02:03:04:0e","6/3/2016","NIC Manufacturer = Microsoft","bob","comp1"