# Adopting Swift Error Constants Migrate existing C code to Swift, using the error constants provided by the System module. ## Discussion The C error constants map to Swift as follows: - `E2BIG` ⟶ [`argListTooLong`](/documentation/System/Errno/argListTooLong) - `EACCES` ⟶ [`permissionDenied`](/documentation/System/Errno/permissionDenied) - `EADDRINUSE` ⟶ [`addressInUse`](/documentation/System/Errno/addressInUse) - `EADDRNOTAVAIL` ⟶ [`addressNotAvailable`](/documentation/System/Errno/addressNotAvailable) - `EAFNOSUPPORT` ⟶ [`addressFamilyNotSupported`](/documentation/System/Errno/addressFamilyNotSupported) - `EAGAIN` ⟶ [`resourceTemporarilyUnavailable`](/documentation/System/Errno/resourceTemporarilyUnavailable) - `EALREADY` ⟶ [`alreadyInProcess`](/documentation/System/Errno/alreadyInProcess) - `EAUTH` ⟶ [`authenticationError`](/documentation/System/Errno/authenticationError) - `EBADARCH` ⟶ [`badCPUType`](/documentation/System/Errno/badCPUType) - `EBADEXEC` ⟶ [`badExecutable`](/documentation/System/Errno/badExecutable) - `EBADF` ⟶ [`badFileDescriptor`](/documentation/System/Errno/badFileDescriptor) - `EBADMACHO` ⟶ [`malformedMachO`](/documentation/System/Errno/malformedMachO) - `EBADMSG` ⟶ [`badMessage`](/documentation/System/Errno/badMessage) - `EBADRPC` ⟶ [`rpcUnsuccessful`](/documentation/System/Errno/rpcUnsuccessful) - `EBUSY` ⟶ [`resourceBusy`](/documentation/System/Errno/resourceBusy) - `ECANCELED` ⟶ [`canceled`](/documentation/System/Errno/canceled) - `ECHILD` ⟶ [`noChildProcess`](/documentation/System/Errno/noChildProcess) - `ECONNABORTED` ⟶ [`connectionAbort`](/documentation/System/Errno/connectionAbort) - `ECONNREFUSED` ⟶ [`connectionRefused`](/documentation/System/Errno/connectionRefused) - `ECONNRESET` ⟶ [`connectionReset`](/documentation/System/Errno/connectionReset) - `EDEADLK` ⟶ [`deadlock`](/documentation/System/Errno/deadlock) - `EDESTADDRREQ` ⟶ [`addressRequired`](/documentation/System/Errno/addressRequired) - `EDEVERR` ⟶ [`deviceError`](/documentation/System/Errno/deviceError) - `EDOM` ⟶ [`outOfDomain`](/documentation/System/Errno/outOfDomain) - `EDQUOT` ⟶ [`diskQuotaExceeded`](/documentation/System/Errno/diskQuotaExceeded) - `EEXIST` ⟶ [`fileExists`](/documentation/System/Errno/fileExists) - `EFAULT` ⟶ [`badAddress`](/documentation/System/Errno/badAddress) - `EFBIG` ⟶ [`fileTooLarge`](/documentation/System/Errno/fileTooLarge) - `EFTYPE` ⟶ [`badFileTypeOrFormat`](/documentation/System/Errno/badFileTypeOrFormat) - `EHOSTDOWN` ⟶ [`hostIsDown`](/documentation/System/Errno/hostIsDown) - `EHOSTUNREACH` ⟶ [`noRouteToHost`](/documentation/System/Errno/noRouteToHost) - `EIDRM` ⟶ [`identifierRemoved`](/documentation/System/Errno/identifierRemoved) - `EILSEQ` ⟶ [`illegalByteSequence`](/documentation/System/Errno/illegalByteSequence) - `EINPROGRESS` ⟶ [`nowInProgress`](/documentation/System/Errno/nowInProgress) - `EINTR` ⟶ [`interrupted`](/documentation/System/Errno/interrupted) - `EINVAL` ⟶ [`invalidArgument`](/documentation/System/Errno/invalidArgument) - `EIO` ⟶ [`ioError`](/documentation/System/Errno/ioError) - `EISCONN` ⟶ [`socketIsConnected`](/documentation/System/Errno/socketIsConnected) - `EISDIR` ⟶ [`isDirectory`](/documentation/System/Errno/isDirectory) - `ELAST` ⟶ [`lastErrnoValue`](/documentation/System/Errno/lastErrnoValue) - `ELOOP` ⟶ [`tooManySymbolicLinkLevels`](/documentation/System/Errno/tooManySymbolicLinkLevels) - `EMFILE` ⟶ [`tooManyOpenFiles`](/documentation/System/Errno/tooManyOpenFiles) - `EMLINK` ⟶ [`tooManyLinks`](/documentation/System/Errno/tooManyLinks) - `EMSGSIZE` ⟶ [`messageTooLong`](/documentation/System/Errno/messageTooLong) - `EMULTIHOP` ⟶ [`multiHop`](/documentation/System/Errno/multiHop) - `ENAMETOOLONG` ⟶ [`fileNameTooLong`](/documentation/System/Errno/fileNameTooLong) - `ENEEDAUTH` ⟶ [`needAuthenticator`](/documentation/System/Errno/needAuthenticator) - `ENETDOWN` ⟶ [`networkDown`](/documentation/System/Errno/networkDown) - `ENETRESET` ⟶ [`networkReset`](/documentation/System/Errno/networkReset) - `ENETUNREACH` ⟶ [`networkUnreachable`](/documentation/System/Errno/networkUnreachable) - `ENFILE` ⟶ [`tooManyOpenFilesInSystem`](/documentation/System/Errno/tooManyOpenFilesInSystem) - `ENOATTR` ⟶ [`attributeNotFound`](/documentation/System/Errno/attributeNotFound) - `ENOBUFS` ⟶ [`noBufferSpace`](/documentation/System/Errno/noBufferSpace) - `ENODATA` ⟶ [`noData`](/documentation/System/Errno/noData) - `ENODEV` ⟶ [`operationNotSupportedByDevice`](/documentation/System/Errno/operationNotSupportedByDevice) - `ENOENT` ⟶ [`noSuchFileOrDirectory`](/documentation/System/Errno/noSuchFileOrDirectory) - `ENOEXEC` ⟶ [`execFormatError`](/documentation/System/Errno/execFormatError) - `ENOLCK` ⟶ [`noLocks`](/documentation/System/Errno/noLocks) - `ENOLINK` ⟶ [`noLink`](/documentation/System/Errno/noLink) - `ENOMEM` ⟶ [`noMemory`](/documentation/System/Errno/noMemory) - `ENOMSG` ⟶ [`noMessage`](/documentation/System/Errno/noMessage) - `ENOPOLICY` ⟶ [`noSuchPolicy`](/documentation/System/Errno/noSuchPolicy) - `ENOPROTOOPT` ⟶ [`protocolNotAvailable`](/documentation/System/Errno/protocolNotAvailable) - `ENOSPC` ⟶ [`noSpace`](/documentation/System/Errno/noSpace) - `ENOSR` ⟶ [`noStreamResources`](/documentation/System/Errno/noStreamResources) - `ENOSTR` ⟶ [`notStream`](/documentation/System/Errno/notStream) - `ENOSYS` ⟶ [`noFunction`](/documentation/System/Errno/noFunction) - `ENOTBLK` ⟶ [`notBlockDevice`](/documentation/System/Errno/notBlockDevice) - `ENOTCONN` ⟶ [`socketNotConnected`](/documentation/System/Errno/socketNotConnected) - `ENOTDIR` ⟶ [`notDirectory`](/documentation/System/Errno/notDirectory) - `ENOTEMPTY` ⟶ [`directoryNotEmpty`](/documentation/System/Errno/directoryNotEmpty) - `ENOTRECOVERABLE` ⟶ [`notRecoverable`](/documentation/System/Errno/notRecoverable) - `ENOTSOCK` ⟶ [`notSocket`](/documentation/System/Errno/notSocket) - `ENOTSUP` ⟶ [`notSupported`](/documentation/System/Errno/notSupported) - `ENOTTY` ⟶ [`inappropriateIOCTLForDevice`](/documentation/System/Errno/inappropriateIOCTLForDevice) - `ENXIO` ⟶ [`noSuchAddressOrDevice`](/documentation/System/Errno/noSuchAddressOrDevice) - `EOPNOTSUPP` ⟶ [`notSupportedOnSocket`](/documentation/System/Errno/notSupportedOnSocket) - `EOVERFLOW` ⟶ [`overflow`](/documentation/System/Errno/overflow) - `EOWNERDEAD` ⟶ [`previousOwnerDied`](/documentation/System/Errno/previousOwnerDied) - `EPERM` ⟶ [`notPermitted`](/documentation/System/Errno/notPermitted) - `EPFNOSUPPORT` ⟶ [`protocolFamilyNotSupported`](/documentation/System/Errno/protocolFamilyNotSupported) - `EPIPE` ⟶ [`brokenPipe`](/documentation/System/Errno/brokenPipe) - `EPROCLIM` ⟶ [`tooManyProcesses`](/documentation/System/Errno/tooManyProcesses) - `EPROCUNAVAIL` ⟶ [`rpcProcedureUnavailable`](/documentation/System/Errno/rpcProcedureUnavailable) - `EPROGMISMATCH` ⟶ [`rpcProgramVersionMismatch`](/documentation/System/Errno/rpcProgramVersionMismatch) - `EPROGUNAVAIL` ⟶ [`rpcProgramUnavailable`](/documentation/System/Errno/rpcProgramUnavailable) - `EPROTONOSUPPORT` ⟶ [`protocolNotSupported`](/documentation/System/Errno/protocolNotSupported) - `EPROTOTYPE` ⟶ [`protocolWrongTypeForSocket`](/documentation/System/Errno/protocolWrongTypeForSocket) - `EPROTO` ⟶ [`protocolError`](/documentation/System/Errno/protocolError) - `EPWROFF` ⟶ [`devicePowerIsOff`](/documentation/System/Errno/devicePowerIsOff) - `EQFULL` ⟶ [`outputQueueFull`](/documentation/System/Errno/outputQueueFull) - `ERANGE` ⟶ [`outOfRange`](/documentation/System/Errno/outOfRange) - `EREMOTE` ⟶ [`tooManyRemoteLevels`](/documentation/System/Errno/tooManyRemoteLevels) - `EROFS` ⟶ [`readOnlyFileSystem`](/documentation/System/Errno/readOnlyFileSystem) - `ERPCMISMATCH` ⟶ [`rpcVersionMismatch`](/documentation/System/Errno/rpcVersionMismatch) - `ESHLIBVERS` ⟶ [`sharedLibraryVersionMismatch`](/documentation/System/Errno/sharedLibraryVersionMismatch) - `ESHUTDOWN` ⟶ [`socketShutdown`](/documentation/System/Errno/socketShutdown) - `ESOCKTNOSUPPORT` ⟶ [`socketTypeNotSupported`](/documentation/System/Errno/socketTypeNotSupported) - `ESPIPE` ⟶ [`illegalSeek`](/documentation/System/Errno/illegalSeek) - `ESRCH` ⟶ [`noSuchProcess`](/documentation/System/Errno/noSuchProcess) - `ESTALE` ⟶ [`staleNFSFileHandle`](/documentation/System/Errno/staleNFSFileHandle) - `ETIMEDOUT` ⟶ [`timedOut`](/documentation/System/Errno/timedOut) - `ETIME` ⟶ [`timeout`](/documentation/System/Errno/timeout) - `ETOOMANYREFS` ⟶ [`tooManyReferences`](/documentation/System/Errno/tooManyReferences) - `ETXTBSY` ⟶ [`textFileBusy`](/documentation/System/Errno/textFileBusy) - `EUSERS` ⟶ [`tooManyUsers`](/documentation/System/Errno/tooManyUsers) - `EWOULDBLOCK` ⟶ [`wouldBlock`](/documentation/System/Errno/wouldBlock) - `EXDEV` ⟶ [`improperLink`](/documentation/System/Errno/improperLink) --- Copyright © 2026 Apple Inc. 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