{"id":4117,"date":"2013-02-24T00:01:00","date_gmt":"2013-02-24T00:01:00","guid":{"rendered":"https:\/\/blogs.technet.microsoft.com\/heyscriptingguy\/2013\/02\/24\/weekend-scripter-two-way-cool-powershell-text-file-tricks-tail-and-wait\/"},"modified":"2013-02-24T00:01:00","modified_gmt":"2013-02-24T00:01:00","slug":"weekend-scripter-two-way-cool-powershell-text-file-tricks-tail-and-wait","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/scripting\/weekend-scripter-two-way-cool-powershell-text-file-tricks-tail-and-wait\/","title":{"rendered":"Weekend Scripter: Two Way-Cool PowerShell Text File Tricks: Tail and Wait"},"content":{"rendered":"

Summary:<\/strong> Microsoft Scripting Guy, Ed Wilson, talks about two way-cool new Windows PowerShell parameters: Tail and Wait.<\/span><\/p>\n

Microsoft Scripting Guy, Ed Wilson, is here. Some things in Windows PowerShell are just so cool that I get all carried away with them and lose focus on whatever I am supposed to be doing. It happens that way sometimes. Luckily, it is the weekend, so I am covered for frittering away my time. But hey, it is for a good cause.<\/p>\n

Note<\/strong>  Today I talk about reading from a log file as it updates. I also talk about reading from the end of a log file. I am using the script I wrote yesterday to add to the log file as I watch for updates. See yesterday’s article, Weekend Scripter: Creating a Sample Log File by Using PowerShell<\/a>, <\/em>for that script and for a discussion of the script.<\/p>\n

Reading x number of lines from beginning or from end of log<\/h2>\n

For log files that log to the end of the file, the most recent information is at the bottom of the file. This can be a problem if I don’t know how many lines of stuff are in the log. Oh, I can do it, but even using Windows PowerShell, it requires a bit of code. Not anymore, because we now have the tail<\/strong> <\/em>parameter that will retrieve a specific number of lines from the very bottom of the file. This technique is shown here.<\/p>\n

PS C:\\> Get-Content -Path C:\\fso\\mylogfile.log -Tail 1<\/p>\n

Added sample 125 at 4:0:42<\/p>\n

PS C:\\> Get-Content -Path C:\\fso\\mylogfile.log -Tail 2<\/p>\n

Added sample 123 at 4:0:42<\/p>\n

Added sample 125 at 4:0:42<\/p>\n

PS C:\\> Get-Content -Path C:\\fso\\mylogfile.log -Tail 3<\/p>\n

Added sample 121 at 4:0:42<\/p>\n

Added sample 123 at 4:0:42<\/p>\n

Added sample 125 at 4:0:42<\/p>\n

If I am interested in the first lines in the file, I use the –head<\/strong> <\/em>parameter and specify how many lines I want to obtain. This is shown here.<\/p>\n

PS C:\\> Get-Content -Path C:\\fso\\mylogfile.log -Head 2<\/p>\n

Added sample 0 at 3:46:40<\/p>\n

Added sample 1 at 3:46:40<\/p>\n

But what about when the action is still occurring?<\/h2>\n

If the action is still occurring, that is, it is still being written to the log file, use the –wait<\/strong> <\/em>parameter of Get-Content<\/strong>. The command is shown here.<\/p>\n

Get-Content -Path C:\\fso\\mylogfile.log -Tail 1 –Wait<\/p>\n

In this way, I retrieve the last written log file entry as it occurs.<\/p>\n

To test this, I run the command above in the Windows PowerShell console. The Windows PowerShell console waits for new lines to be written to the file. I then switch to the Windows PowerShell ISE and run my Add-LogV2.ps1 script so that new entries are added to the file.<\/p>\n

I switch back to the Windows PowerShell console and watch the entries add new lines to the Windows PowerShell console. The result is shown in the following image.<\/p>\n

\"Image<\/a><\/p>\n

Well, that is about it for monitoring a log file. Join me tomorrow when I will talk about parsing the System event log.<\/p>\n

I invite you to follow me on Twitter<\/a> and Facebook<\/a>. If you have any questions, send email to me at scripter@microsoft.com<\/a>, or post your questions on the Official Scripting Guys Forum<\/a>. See you tomorrow. Until then, peace.<\/p>\n

Ed Wilson, Microsoft Scripting Guy<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

Summary: Microsoft Scripting Guy, Ed Wilson, talks about two way-cool new Windows PowerShell parameters: Tail and Wait. Microsoft Scripting Guy, Ed Wilson, is here. Some things in Windows PowerShell are just so cool that I get all carried away with them and lose focus on whatever I am supposed to be doing. It happens that […]<\/p>\n","protected":false},"author":596,"featured_media":87096,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[362,3,4,14,61,45],"class_list":["post-4117","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-scripting","tag-powershell-3","tag-scripting-guy","tag-scripting-techniques","tag-text-files","tag-weekend-scripter","tag-windows-powershell"],"acf":[],"blog_post_summary":"

Summary: Microsoft Scripting Guy, Ed Wilson, talks about two way-cool new Windows PowerShell parameters: Tail and Wait. Microsoft Scripting Guy, Ed Wilson, is here. Some things in Windows PowerShell are just so cool that I get all carried away with them and lose focus on whatever I am supposed to be doing. It happens that […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts\/4117","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/users\/596"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/comments?post=4117"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts\/4117\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/media\/87096"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/media?parent=4117"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/categories?post=4117"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/tags?post=4117"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}