Error handling of Linux system programming

In the Linux system programming, when the system call error, there is an integer variable will be set, this integer variable is errno, the definition of this variable in the/usr/include/errno.h file

1 #ifndef _errno_h2 3 /*The Includer defined __need_emath If he wants only the definitions4 of EDOM and Erange, and not everything else. */5 #ifndef __need_emath6# define _errno_h17# include <features.h>8 #endif9 Ten __begin_decls One  A /*Get the error number constants from the System-specific file. - This file would test __need_emath and _errno_h. */ -#include <bits/errno.h> the #undef__need_emath -  - #ifdef _errno_h -  + /*Declare the ' errno ' variable, unless it ' s defined as a macro by - bits/errno.h. The case in GNU, where it's a per-thread + variable. This redeclaration using the macro still works, but it A would be a function declaration without a prototype and may trigger at a-wstrict-prototypes warning. */ - #ifndef errno -  extern int  errno;  - #endif -  - #ifdef __USE_GNU in  - /*The full and simple forms of the The name with which the to invoked. These variables is set up automatically at startup based on + The value of argv[0] (this works with the GNU LD). */ - extern Char*program_invocation_name, *Program_invocation_short_name; the #endif/* __USE_GNU */ * #endif/* _errno_h */ $ Panax Notoginseng __end_decls -  the #endif/* _errno_h */ +  A /*The Hurd <bits/errno.h> defines ' error_t ' as an enumerated type so the That's printing ' error_t ' values in the debugger shows the names. We + might need this definition sometimes even if the this file is included - before. */ $ #ifDefined __use_gnu | | Defined __need_error_t $ # ifndef __error_t_defined -typedefinterror_t; -# define __error_t_defined1 the # endif - # undef __need_error_tWuyi #endif

When there is no error in the system call, the integer variable is set to a value, each value has a special meaning, each value is represented by a macro, defined in the/usr/include/asm-generic/errno.h file

#ifndef _asm_generic_errno_h#define_asm_generic_errno_h#include<asm-generic/errno-Base.h>#defineEDEADLK//Resource deadlock would occur * *#defineEnametoolong/* File name too long */#defineEnolck Notoginseng */No record locks available */#defineEnosys/* Function not implemented */#defineEnotempty/* Directory not empty */#defineEloop/* Too Many symbolic links encountered * *#defineEwouldblock Eagain/* operation would block */#defineENOMSG * * No message of desired type */#defineEIDRM */Identifier removed */#defineECHRNG */* Channel number out of range */#defineEl2nsync */Level 2 not synchronized */#defineEL3HLT/* Level 3 halted */#defineEl3rst/* Level 3 Reset */#defineELNRNG/* Link number out of range */#defineEunatch */Protocol driver not attached */#defineENOCSI/* NO CSI structure available */#defineEL2HLT/* Level 2 halted */#defineEbade/* Invalid Exchange * *#defineEBADR-*/Invalid Request Descriptor */#defineExfull/* Exchange full */#defineEnoano/* No anode */#defineEBADRQC */Invalid Request code */#defineEBADSLT/* Invalid slot */#defineEdeadlock Edeadlk#defineEbfont/* Bad font file format */#defineENOSTR/* Device not a stream */#defineEnodata/* NO data available */#defineETime */* Timer expired */#defineENOSR */* out of streams resources * *#defineEnonet */Machine was not on the network */#defineENOPKG/* Package not installed */#defineEremote/* Object is remote */#defineEnolink/* Link has been severed */#defineEADV/* Advertise Error */#defineESRMNT/* Srmount Error */#defineECOMM/* Communication error on Send */#defineEproto/* Protocol Error */#defineEmultihop */Multihop attempted * *#defineEdotdot/* RFS specific Error */#defineEBADMSG-*/Not a data message */#defineEoverflow */Value too large for defined data type */#defineEnotuniq/* Name not unique on network */#defineEBADFD */* File descriptor in Bad state */#defineEREMCHG/* Remote address changed */#defineELIBACC/* Can not access a needed shared library */#defineElibbad */Accessing a corrupted shared library */#defineELIBSCN Bayi/* lib section in a.out corrupted */#defineElibmax/attempting to link in too many shared libraries */#defineElibexec */cannot exec a shared library directly */#defineEILSEQ/* Illegal byte sequence */#defineErestart/* Interrupted system call should be restarted */#defineEstrpipe */* Streams pipe Error */#defineEusers */Too Many users * *#defineEnotsock */* Socket operation on Non-socket */#defineEdestaddrreq/* Destination address required */#defineEmsgsize/* Message too long */#defineEprototype/* Protocol wrong type for socket */#defineEnoprotoopt */Protocol Not available */#defineEprotonosupport */Protocol not supported */#defineEsocktnosupport 94/* Socket type not supported */#defineEopnotsupp */Operation not supported on transport endpoint * *#defineEpfnosupport */Protocol family not supported */#defineEafnosupport/* Address family not supported by protocol */#defineEaddrinuse 98/* Address already in use */#defineEaddrnotavail/* Cannot assign requested address * *#defineEnetdown/* Network is down */#defineEnetunreach 101/* Network is unreachable */#defineEnetreset 102/* Network dropped connection because of reset */#defineEconnaborted 103/* Software caused connection abort */#defineEconnreset 104/* Connection Reset by Peer */#defineENOBUFS * * No buffer space Available */#defineEisconn 106/* Transport endpoint is already connected * *#defineEnotconn 107/* Transport endpoint is not connected */#defineEshutdown 108/* Cannot send after transport endpoint shutdown */#defineEtoomanyrefs 109/* Too many references:cannot splice * *#defineEtimedout */Connection timed out */#defineEconnrefused 111/* Connection refused */#defineEhostdown * * * Host is down */#defineEhostunreach 113/* No route to host */#defineEalready */Operation already in progress */#defineEinprogress-*/Operation now in progress */#defineEstale */* Stale NFS file handle */#defineEuclean 117/* Structure needs cleaning * *#defineEnotnam 118/* Not a XENIX named type file */#defineEnavail 119 */No XENIX semaphores Available * *#defineEisnam/* is a named type file */#defineEremoteio 121/* Remote I/O error */#defineEdquot 122/* Quota exceeded */#defineEnomedium 123 */No medium found */#defineEmediumtype 124/* Wrong medium type */#defineecanceled/* Operation Canceled */#defineEnokey 126/* Required key not available */#defineEkeyexpired 127/* Key has expired */#defineekeyrevoked/* Key has been revoked */#defineEkeyrejected 129/* Key was rejected by service *//*For robust mutexes*/#defineEownerdead/* Owner died */#defineEnotrecoverable 131/* State not recoverable */#defineErfkill */Operation not possible due to Rf-kill * *#defineEhwpoison 133/* Memory page has hardware error */#endif

After explaining the meaning of errno, let's use two common error output functions

One is perror.

void perror (constchar *s); // output error messages                          based on the value of the errno set by the system // the error message will contain the contents of the programmer's own content, with parameters s passed to the programmer to output the content

One is strerror.

Char *strerror (int errnum); // errno is passed into the function strerror, STRERROR returns the text of the corresponding error message

Error handling of Linux system programming