该头文件引入 C 标准库头文件 <errno.h>，并将相关标识符加入 std 命名空间。

1 说明

包含该头文件，可以保证 C 标准库头文件中具有外部链接的名称会在 std 命名空间中进行声明。

语法：

#include<cerrno>

宏：

#defineerrno#defineE2BIG#defineEACCES#defineEADDRINUSE#defineEADDRNOTAVAIL#defineEAFNOSUPPORT#defineEAGAIN#defineEALREADY#defineEBADF#defineEBADMSG#defineEBUSY#defineECANCELED#defineECHILD#defineECONNABORTED#defineECONNREFUSED#defineECONNRESET#defineEDEADLK#defineEDESTADDRREQ#defineDEOM#defineEEXIST#defineEFAULT#defineEFBIG#defineEHOSTUNREACH#defineEIDRM#defineEILSEQ#defineEINPROGRESS#defineEINTR#defineEINVAL#defineEIO#defineEISCONN#defineEISDIR#defineELOOP#defineEMFILE#defineEMLINK#defineEMSGSIZE#defineENAMETOOLONG#defineENETDOWN#defineENETRESET#defineENETUNREACH#defineENFILE#defineENOBUFS#defineENODATA#defineENODEV#defineENOENT#defineENOEXEC#defineENOLCK#defineENOLINK#defineENOMEM#defineENOMSG#defineENOPROTOOPT#defineENOSPC#defineENOSR#defineENOSTR#defineENOSYS#defineENOTCONN#defineENOTDIR#defineENOTEMPTY#defineENOTRECOVERABLE#defineENOTSOCK#defineENOTSUP#defineENOTTY#defineENXIO#defineEOPNOTSUPP#defineEOVERFLOW#defineEOWNERDEAD#defineEPERM#defineEPIPE#defineEPROTO#defineEPROTONOSUPPORT#defineEPROTOTYPE#defineERANGE#defineEROFS#defineESPIPE#defineESRCH#defineETIME#defineETIMEDOUT#defineETXTBSY#defineEWOULDBLOCK#defineEXDEV

备注📚：

• 这里的全部宏均由POSIX标准所定义；
• 使用提示：errno用于保存系统调用、库函数出错后的错误码；现代实现中它是线程局部变量。应当在函数调用失败后立刻读取，后续库函数调用可能覆盖该值。