| UMask | Darcs.Flags, Darcs.Arguments |
| umaskOption | Darcs.Arguments |
| unadd | Darcs.Commands.Remove |
| unavailable | Darcs.Hopefully |
| Uncachable | URL, Darcs.External |
| UnCompress | Darcs.Flags, Darcs.Arguments |
| uncompressNocompress | Darcs.Arguments |
| unDoc | Printer |
| unFreeLeft | Darcs.Witnesses.Sealed |
| unFreeRight | Darcs.Witnesses.Sealed |
| unidiff | Darcs.Arguments |
| Unified | Darcs.Flags, Darcs.Arguments |
| unified | Darcs.Arguments |
| Union | Darcs.Flags, Darcs.Arguments |
| unionCaches | Darcs.Repository.Cache |
| unionRemoteCaches | Darcs.Repository.Cache |
| Unknown | |
| 1 (Data Constructor) | Darcs.Patch.Prim |
| 2 (Data Constructor) | Darcs.Patch.Commute |
| unlinesPS | ByteStringUtils |
| unNon | Darcs.Patch.Non |
| unpackPSFromUTF8 | ByteStringUtils |
| unpull | Darcs.Commands.Unrecord |
| unravel | Darcs.Patch.Commute |
| unrecord | Darcs.Commands.Unrecord |
| unrecordedChanges | Darcs.Repository.State, Darcs.Repository |
| unrevert | Darcs.Commands.Unrevert |
| unrevertUrl | Darcs.Repository.Internal, Darcs.Repository |
| unsafeBoth | Printer |
| unsafeBothText | Printer |
| unsafeChar | Printer |
| unsafeCoerceP | Darcs.Witnesses.Ordered |
| unsafeCoerceP2 | Darcs.Witnesses.Ordered |
| unsafeCoercePEnd | Darcs.Witnesses.Ordered |
| unsafeCoercePStart | Darcs.Witnesses.Ordered |
| unsafeCompare | Darcs.Witnesses.Ordered |
| unsafeMap_l2f | Darcs.Witnesses.Ordered |
| unsafePackedString | Printer |
| unsafeText | Printer |
| unsafeToCalendarTime | IsoDate |
| unsafeUnRIO | Darcs.Repository.Internal |
| unsafeUnseal | Darcs.Witnesses.Sealed |
| unsafeUnseal2 | Darcs.Witnesses.Sealed |
| unsafeUnsealFlipped | Darcs.Witnesses.Sealed |
| unsafeWithInternals | ByteStringUtils |
| unseal | Darcs.Witnesses.Sealed |
| unseal2 | Darcs.Witnesses.Sealed |
| unsealFlipped | Darcs.Witnesses.Sealed |
| unsealM | Darcs.Witnesses.Sealed |
| unsetTime | IsoDate |
| unWPatchInfo | Darcs.Hopefully |
| UpdatePristine | |
| 1 (Type/Class) | Darcs.Repository.Internal |
| 2 (Data Constructor) | Darcs.Repository.Internal |
| UpgradeFormat | Darcs.Flags, Darcs.Arguments |
| upgradeFormat | Darcs.Arguments |
| UpToPatch | Darcs.Flags, Darcs.Arguments |
| UpToPattern | Darcs.Flags, Darcs.Arguments |
| UpToTag | Darcs.Flags, Darcs.Arguments |
| usage | Darcs.Commands |
| usageHelper | Darcs.Commands |
| useAbsoluteOrStd | Darcs.RepoPath |
| useExternalMerge | Darcs.Arguments |
| UseFormat2 | Darcs.Flags, Darcs.Arguments |
| UseHashedInventory | Darcs.Flags, Darcs.Arguments |
| UseOldFashionedInventory | Darcs.Flags, Darcs.Arguments |
| userchunk | Printer |
| userchunkP | Printer |
| userchunkPS | Printer |
| utf8ToLocale | ByteStringUtils |