I run a powershell script.... scheduled to run every day. Make sure whereever you're hosting has access as well as Powershell Version 4 or newer (I use 5 currently). Check powershell version with $PSVersionTable.PSVersion.
Follow instructions on that site to get your token, then fill it in the bearer token below...
Use at your own risk. You need to build out error handling and logging. Also, directory checks for items that already exist/move items if you want to archive previous exports. GL.
$BearerToken = ''
$headers = New-Object "System.Collections.Generic.Dictionary[[String],[String]]"
$headers.Add("Authorization", "Bearer $BearerToken")
$headers.Add("Accept",'*/*')
$headers.Add("accept-encoding", "zip")
#Base Directory where you want these files to be saved locally
$dir = ''
$currentfile = "$($dir)\current\messages.csv"
# You can use a relative date range for the export as well, by building out a date object
$export = "https://www.yammer.com/api/v1/export?since=2015-01-01T00:00:00&include=csv"
#Create logs for your files.
$log_file = "$($dir)\log\{0:yyyy-MM}_Export.log" -f (get-date)
#Example to add logs -- $logmsg = "This is my log"
# Add-content $log_file "$logmsg"
#Two lines inside the Try is actually where the attempts work. I found there to be issues so I put them in different areas for download, then download is complete, unzip.
Try
{
invoke-webrequest -uri $export -method get -headers $headers -OutFile $dir\export.zip }
Expand-archive -path $dir\export.zip -dest $dir\current -f
Catch
{
#Error Handling goes here
}
