| UMask | Darcs.Flags, Darcs.Arguments |
| umaskOption | Darcs.Arguments |
| unadd | Darcs.Commands.Remove |
| unavailable | Darcs.Patch.PatchInfoAnd |
| unBracketed | Darcs.Patch.Bracketed |
| unBracketedFL | Darcs.Patch.Bracketed |
| Uncachable | URL.Request, 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 | Darcs.Patch.Prim.V1.Commute |
| unlinesPS | ByteStringUtils |
| unNon | Darcs.Patch.V2.Non |
| unpackPSFromUTF8 | ByteStringUtils |
| unpull | Darcs.Commands.Unrecord |
| unravel | Darcs.Patch.V1.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.Unsafe |
| unsafeCoerceP1 | Darcs.Witnesses.Unsafe |
| unsafeCoerceP2 | Darcs.Witnesses.Unsafe |
| unsafeCoercePEnd | Darcs.Witnesses.Unsafe |
| unsafeCoercePStart | Darcs.Witnesses.Unsafe |
| unsafeCompare | Darcs.Witnesses.Eq |
| 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.Patch.PatchInfoAnd |
| 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 |
| url | URL.Request |
| urlOf | Darcs.URL |
| UrlRequest | |
| 1 (Type/Class) | URL.Request |
| 2 (Data Constructor) | URL.Request |
| UrlState | |
| 1 (Type/Class) | URL.Request |
| 2 (Data Constructor) | URL.Request |
| usage | Darcs.Commands |
| usageHelper | Darcs.Commands |
| useAbsoluteOrStd | Darcs.RepoPath |
| useExternalMerge | Darcs.Arguments |
| UseFormat2 | Darcs.Flags, Darcs.Arguments |
| UseHashedInventory | Darcs.Flags, Darcs.Arguments |
| UseIndex | |
| 1 (Type/Class) | Darcs.Flags, Darcs.Repository.State |
| 2 (Data Constructor) | Darcs.Flags, Darcs.Repository.State |
| UseNoWorkingDir | Darcs.Flags, Darcs.Arguments |
| usePacks | |
| 1 (Function) | Darcs.Flags |
| 2 (Function) | Darcs.Arguments |
| userchunk | Printer |
| userchunkP | Printer |
| userchunkPS | Printer |
| UseWorkingDir | Darcs.Flags, Darcs.Arguments |
| useWorkingDir | Darcs.Arguments |
| UUID | |
| 1 (Type/Class) | Darcs.Patch.Prim.V3.ObjectMap, Darcs.Patch.Prim.V3.Core |
| 2 (Data Constructor) | Darcs.Patch.Prim.V3.ObjectMap, Darcs.Patch.Prim.V3.Core |