Labels

Tuesday, March 18, 2008

260+ character MAX_PATH limitations in filenames

Accessing files with a full path\filename of greater than the traditional MAX_PATH constant of 260 characters can still be challenging in today's Operating Systems. This article provides some insight into the problem, and methods to identify and workaround the issue.

Identifying the problem

The problem occurs through common applications, explorer, Office apps, command prompt, and sometimes returns meaningful errors (the full path 'x' is too long – md/mkdir) but often returns nothing (explorer) or an obscure error.

One method I use to identify these problems – particularly because they usually occur when trying to copy the data – is robocopy.


The verbose logs from a robocopy command will identify this particular error with a general syntax error, but it's easy enough to tell with the path referenced if it's a 260+ problem. The text logged by robocopy (version XP010 in this case) is:
"ERROR 123 (0x0000007B)"

Testing

Testing was completed, showing that:

  • The server name and share name definitely do count as part of
    the total 260 character path limitation when using UNC references, eg file://server/share
  • However, when using a mapped drive, the server name and share
    name are irrelevant; it is the constructed path with the drive letter that counts, eg: f:\
  • Despite various Microsoft articles, using the \\?\ syntax to
    disable path parsing does not force use of the Unicode equivalent function (which didn't really make sense anyway).

Workaround

Three successful methods to work around this issue have been tested, detailed below.

Method 1 - Use a utility that can bypass the 260 character limitations by using the Unicode version of the CopyFile() function (CopyFileW).

I used a utility called FastCopy, which supports paths longer than 260 characters, presumably by using the Unicode version of the relevant functions.

Method 2 - Use the 8.3 short filenames generated by the filesystem to reduce the path.

This didn't occur to me until I was nearly finished with this exercise, and while it's easier to access individual files in this way, batching this to copy disparate files is not so easy.

Method 3 - Create a share deeper in the directory path, and access the file through the share, either UNC or mapped drive.

This isn't very practical in most situations, but if it's possible to create new shares, this is probably the easiest method.

Other testing completed:

  • Copying through explorer also has the same results.
  • Tried with the "\\?\f:\" syntax, which made the problem worse (because of the extra few characters), even though this is supposed to bypass 260 character limitations using the Unicode function.
  • Accessing the file locally on the 2003 SP2 R2 server, or
    remotely via XPSP2 has the same result (with a mapped drive)

References

CopyFile function

http://msdn2.microsoft.com/en-us/library/aa363851(VS.85).aspx

Naming a Volume
http://msdn2.microsoft.com/en-us/library/aa365248(VS.85).aspx

Making Room for Long Filenames
http://msdn2.microsoft.com/en-us/library/ms810456.aspx

Naming a File
http://msdn2.microsoft.com/en-us/library/aa365247.aspx


Wayne's World of IT (WWoIT), Copyright 2008 Wayne Martin.

1 comment:

SteveAD said...

For such problems, you can use Long Path Tool, it works good I will say.


All Posts

printQueue AD objects for 2003 ClusterVirtualCenter Physical to VirtualVirtual 2003 MSCS Cluster in ESX VI3
Finding duplicate DNS recordsCommand-line automation – Echo and macrosCommand-line automation – set
Command-line automation - errorlevels and ifCommand-line automation - find and findstrBuilding blocks of command-line automation - FOR
Useful PowerShell command-line operationsMSCS 2003 Cluster Virtual Server ComponentsServer-side process for simple file access
OpsMgr 2007 performance script - VMware datastores...Enumerating URLs in Internet ExplorerNTLM Trusts between 2003 and NT4
2003 Servers with Hibernation enabledReading Shortcuts with PowerShell and VBSModifying DLL Resources
Automatically mapping printersSimple string encryption with PowerShellUseful NTFS and security command-line operations
Useful Windows Printer command-line operationsUseful Windows MSCS Cluster command-line operation...Useful VMware ESX and VC command-line operations
Useful general command-line operationsUseful DNS, DHCP and WINS command-line operationsUseful Active Directory command-line operations
Useful command-linesCreating secedit templates with PowerShellFixing Permissions with NTFS intra-volume moves
Converting filetime with vbs and PowerShellDifference between bat and cmdReplica Domain for Authentication
Troubleshooting Windows PrintingRenaming a user account in ADOpsMgr 2007 Reports - Sorting, Filtering, Charting...
WMIC XSL CSV output formattingEnumerating File Server ResourcesWMIC Custom Alias and Format
AD site discoveryPassing Parameters between OpsMgr and SSRSAnalyzing Windows Kernel Dumps
Process list with command-line argumentsOpsMgr 2007 Customized Reporting - SQL QueriesPreventing accidental NTFS data moves
FSRM and NTFS Quotas in 2003 R2PowerShell Deleting NTFS Alternate Data StreamsNTFS links - reparse, symbolic, hard, junction
IE Warnings when files are executedPowerShell Low-level keyboard hookCross-forest authentication and GP processing
Deleting Invalid SMS 2003 Distribution PointsCross-forest authentication and site synchronizati...Determining AD attribute replication
AD Security vs Distribution GroupsTroubleshooting cross-forest trust secure channels...RIS cross-domain access
Large SMS Web Reports return Error 500Troubleshooting SMS 2003 MP and SLPRemotely determine physical memory
VMware SDK with PowershellSpinning Excel Pie ChartPoke-Info PowerShell script
Reading web content with PowerShellAutomated Cluster File Security and PurgingManaging printers at the command-line
File System Filters and minifiltersOpsMgr 2007 SSRS Reports using SQL 2005 XMLAccess Based Enumeration in 2003 and MSCS
Find VM snapshots in ESX/VCComparing MSCS/VMware/DFS File & PrintModifying Exchange mailbox permissions
Nested 'for /f' catch-allPowerShell FindFirstFileW bypassing MAX_PATHRunning PowerSell Scripts from ASP.Net
Binary <-> Hex String files with PowershellOpsMgr 2007 Current Performance InstancesImpersonating a user without passwords
Running a process in the secure winlogon desktopShadow an XP Terminal Services sessionFind where a user is logged on from
Active Directory _msdcs DNS zonesUnlocking XP/2003 without passwords2003 Cluster-enabled scheduled tasks
Purging aged files from the filesystemFinding customised ADM templates in ADDomain local security groups for cross-forest secu...
Account Management eventlog auditingVMware cluster/Virtual Center StatisticsRunning scheduled tasks as a non-administrator
Audit Windows 2003 print server usageActive Directory DiagnosticsViewing NTFS information with nfi and diskedit
Performance Tuning for 2003 File ServersChecking ESX/VC VMs for snapshotsShowing non-persistent devices in device manager
Implementing an MSCS 2003 server clusterFinding users on a subnetWMI filter for subnet filtered Group Policy
Testing DNS records for scavengingRefreshing Computer Account AD Group MembershipTesting Network Ports from Windows
Using Recovery Console with RISPAE Boot.ini Switch for DEP or 4GB+ memoryUsing 32-bit COM objects on x64 platforms
Active Directory Organizational Unit (OU) DesignTroubleshooting computer accounts in an Active Dir...260+ character MAX_PATH limitations in filenames
Create or modify a security template for NTFS perm...Find where a user is connecting from through WMISDDL syntax in secedit security templates

About Me

I’ve worked in IT for over 20 years, and I know just about enough to realise that I don’t know very much.