Check In All Documents in a SharePoint Library using PowerShell

Requirement: Check-in All files which are checked out in a SharePoint document library.

How to Check In all checked out documents in SharePoint 2013:
SharePoint 2013 makes it simpler by providing context sensitive ribbon buttons to check in multiple files in bulk. Simply select all files which are checked-out and click on "Check In" button from the ribbon.
Butthis method doesn't work when you have any required field with no default value assigned!

Check In All Documents in a SharePoint Library using PowerShell
When you do Multiple file upload (bulk upload or through explorer view) and your required column doesn't has any default value in it, then your files will be checked-out automatically. The "Check In" button won't work when you miss-out any required fields in the library.

So, our solution is: PowerShell.

PowerShell script to check in all documents in the library:

Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue

#Variables for Site URL and Library Name
$WebURL="http://sharepoint.crescent.com/sites/sales"
$LibraryName="Proposal Documents"

#Get Site and Library
$Web = Get-SPWeb $WebURL
$DocLib = $Web.Lists.TryGetList($LibraryName)

#Get all Checked out files
$CheckedOutFiles = $DocLib.Items | Where-Object { $_.File.CheckOutStatus -ne "None"} 

#Check in All Checked out Files in the library
ForEach($item in $CheckedOutFiles)
    { 
        #If you want to update fields
        #$item["Field"] = "value"
        #$item.SystemUpdate()

        #check in file programmatically     
        #$item.TakeoverCheckout() 
        $DocLib.GetItemById($item.Id).file.CheckIn("Checked in by Admin") 
        write-host "File:'$($item.Name)' has been checked in!"         
    }

If you want to do this for all libraries in your entire SharePoint web application, use: Find All Checked Out Files and Check-In them Back