转自：https://www.cnblogs.com/Jimmy1988/p/7485133.html
1. 错误码 / errno
Linux中系统调用的错误都存储于 errno中，errno由操作系统维护，存储就近发生的错误，即下一次的错误码会覆盖掉上一次的错误。
PS: 只有当系统调用或者调用lib函数时出错，才会置位
errno！
查看系统中所有的errno所代表的含义，可以采用如下的代码：
/* Function: obtain the errno string* char *strerror(int errno)*/#include#include //for strerror() //#include int main() { int tmp = 0; for(tmp = 0; tmp <=256; tmp++) { printf("errno: %2d\t%s\n",tmp,strerror(tmp)); } return 0; }
输出信息如下：
errno: 0 Successerrno: 1 Operation not permittederrno: 2 No such file or directoryerrno: 3 No such processerrno: 4 Interrupted system callerrno: 5 Input/output error errno: 6 No such device or address errno: 7 Argument list too long errno: 8 Exec format error errno: 9 Bad file descriptor errno: 10 No child processes errno: 11 Resource temporarily unavailable errno: 12 Cannot allocate memory errno: 13 Permission denied errno: 14 Bad address errno: 15 Block device required errno: 16 Device or resource busy errno: 17 File exists errno: 18 Invalid cross-device link errno: 19 No such device errno: 20 Not a directory errno: 21 Is a directory errno: 22 Invalid argument errno: 23 Too many open files in system errno: 24 Too many open files errno: 25 Inappropriate ioctl for device errno: 26 Text file busy errno: 27 File too large errno: 28 No space left on device errno: 29 Illegal seek errno: 30 Read-only file system errno: 31 Too many links errno: 32 Broken pipe errno: 33 Numerical argument out of domain errno: 34 Numerical result out of range errno: 35 Resource deadlock avoided errno: 36 File name too long errno: 37 No locks available errno: 38 Function not implemented errno: 39 Directory not empty errno: 40 Too many levels of symbolic links errno: 41 Unknown error 41 errno: 42 No message of desired type errno: 43 Identifier removed errno: 44 Channel number out of range errno: 45 Level 2 not synchronized errno: 46 Level 3 halted errno: 47 Level 3 reset errno: 48 Link number out of range errno: 49 Protocol driver not attached errno: 50 No CSI structure available errno: 51 Level 2 halted errno: 52 Invalid exchange errno: 53 Invalid request descriptor errno: 54 Exchange full errno: 55 No anode errno: 56 Invalid request code errno: 57 Invalid slot errno: 58 Unknown error 58 errno: 59 Bad font file format errno: 60 Device not a stream errno: 61 No data available errno: 62 Timer expired errno: 63 Out of streams resources errno: 64 Machine is not on the network errno: 65 Package not installed errno: 66 Object is remote errno: 67 Link has been severed errno: 68 Advertise error errno: 69 Srmount error errno: 70 Communication error on send errno: 71 Protocol error errno: 72 Multihop attempted errno: 73 RFS specific error errno: 74 Bad message errno: 75 Value too large for defined data type errno: 76 Name not unique on network errno: 77 File descriptor in bad state errno: 78 Remote address changed errno: 79 Can not access a needed shared library errno: 80 Accessing a corrupted shared library errno: 81 .lib section in a.out corrupted errno: 82 Attempting to link in too many shared libraries errno: 83 Cannot exec a shared library directly errno: 84 Invalid or incomplete multibyte or wide character errno: 85 Interrupted system call should be restarted errno: 86 Streams pipe error errno: 87 Too many users errno: 88 Socket operation on non-socket errno: 89 Destination address