How to run “Search-UnifiedAuditLog” in unattended way, i.e. non-interactive.
What are the minimal permissions required?

The PowerShell code:

$clientId = ""
$cPwd = ConvertTo-SecureString -String "" -AsPlainText -Force

$cPath = ""C:\Users\UserName\Certificates\Cert.pfx""
$organization = "contoso.onmicrosoft.com"

Connect-ExchangeOnline -CertificateFilePath $cPath -CertificatePassword $cPwd -AppID $clientId -Organization $organization

[DateTime]$start = [DateTime]::UtcNow.AddMinutes(-45)
[DateTime]$end = [DateTime]::UtcNow
$resultSize = 1000

$results = $null
$results = Search-UnifiedAuditLog -StartDate $start -EndDate $end -ResultSize $results.Count
$results | Select-Object RecordType, CreationDate, UserIds, Operations -First 3

Disconnect-ExchangeOnline -Confirm:$false

Troubleshooting

The error “The term ‘Search-UnifiedAuditLog’ is not recognized”:

Search-UnifiedAuditLog: C:\scripts\PowerShell.auth\Search-AuditLog-w-App.ps1:16:12
Line |
16 | $results = Search-UnifiedAuditLog -StartDate $start -EndDate $end -Re …
| ~~~~~~
| The term 'Search-UnifiedAuditLog' is not recognized as a name of a cmdlet, function, script file, or executable
| program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

means a proper administrative role (e.g. “Exchange administrator”) is not assigned.

References

• Modern Auth and Unattended Scripts in Exchange Online PowerShell V2