errno记录系统的最后一次错误代码，是一个int型，在errno.h中定义，以下程序用于输出errno所代表的含义，0~133有意义，其余的属于未定义。
#include<errno.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main(int argc, const char *argv[])
{
int i = 0;
for(i = 0;i<256;++i)
printf("errno.%02d is: %s\n",i,strerror(i));
return 0;
}
errno.00 is: Success
errno.01 is: Operation not permitted
errno.02 is: No such file or directory
errno.03 is: No such process
errno.04 is: Interrupted system call
errno.05 is: Input/output error
errno.06 is: No such device or address
errno.07 is: Argument list too long
errno.08 is: Exec format error
errno.09 is: Bad file descriptor
errno.10 is: No child processes
errno.11 is: Resource temporarily unavailable
errno.12 is: Cannot allocate memory
errno.13 is: Permission denied
errno.14 is: Bad address
errno.15 is: Block device required
errno.16 is: Device or resource busy
errno.17 is: File exists
errno.18 is: Invalid cross-device link
errno.19 is: No such device
errno.20 is: Not a directory
errno.21 is: Is a directory
errno.22 is: Invalid argument
errno.23 is: Too many open files in system
errno.24 is: Too many open files
errno.25 is: Inappropriate ioctl for device
errno.26 is: Text file busy
errno.27 is: File too large
errno.28 is: No space left on device
errno.29 is: Illegal seek
errno.30 is: Read-only file system
errno.31 is: Too many links
errno.32 is: Broken pipe
errno.33 is: Numerical argument out of domain
errno.34 is: Numerical result out of range
errno.35 is: Resource deadlock avoided
errno.36 is: File name too long
errno.37 is: No locks available
errno.38 is: Function not implemented
errno.39 is: Directory not empty
errno.40 is: Too many levels of symbolic links
errno.41 is: Unknown error 41
errno.42 is: No message of desired type
errno.43 is: Identifier removed
errno.44 is: Channel number out of range
errno.45 is: Level 2 not synchronized
errno.46 is: Level 3 halted
errno.47 is: Level 3 reset
errno.48 is: Link number out of range
errno.49 is: Protocol driver not attached
errno.50 is: No CSI structure available
errno.51 is: Level 2 halted
errno.52 is: Invalid exchange
errno.53 is: Invalid request descriptor
errno.54 is: Exchange full
errno.55 is: No anode
errno.56 is: Invalid request code
errno.57 is: Invalid slot
errno.58 is: Unknown error 58
errno.59 is: Bad font file format
errno.60 is: Device not a stream
errno.61 is: No data available
errno.62 is: Timer expired
errno.63 is: Out of streams resources
errno.64 is: Machine is not on the network
errno.65 is: Package not installed
errno.66 is: Object is remote
errno.67 is: Link has been severed
errno.68 is: Advertise error
errno.69 is: Srmount error
errno.70 is: Communication error on send
errno.71 is: Protocol error
errno.72 is: Multihop attempted
errno.73 is: RFS specific error
errno.74 is: Bad message
errno.75 is: Value too large for defined data type
errno.76 is: Name not unique on network
errno.77 is: File descriptor in bad state
errno.78 is: Remote address changed
errno.79 is: Can not access a needed shared library
errno.80 is: Accessing a corrupted shared library
errno.81 is: .lib section in a.out corrupted
errno.82 is: Attempting to link in too many shared libraries
errno.83 is: Cannot exec a shared library directly
errno.84 is: Invalid or incomplete multibyte or wide character
errno.85 is: Interrupted system call should be restarted
errno.86 is: Streams pipe error
errno.87 is: Too many users
errno.88 is: Socket operation on non-socket
errno.89 is: Destination address required
errno.90 is: Message too long
errno.91 is: Protocol wrong type for socket
errno.92 is: Protocol not available
errno.93 is: Protocol not supported
errno.94 is: Socket type not supported
errno.95 is: Operation not supported
errno.96 is: Protocol family not supported
errno.97 is: Address family not supported by protocol
errno.98 is: Address already in use
errno.99 is: Cannot assign requested address
errno.100 is: Network is down
errno.101 is: Network is unreachable
errno.102 is: Network dropped connection on reset
errno.103 is: Software caused connection abort
errno.104 is: Connection reset by peer
errno.105 is: No buffer space available
errno.106 is: Transport endpoint is already connected
errno.107 is: Transport endpoint is not connected
errno.108 is: Cannot send after transport endpoint shutdown
errno.109 is: Too many references: cannot splice
errno.110 is: Connection timed out
errno.111 is: Connection refused
errno.112 is: Host is down
errno.113 is: No route to host
errno.114 is: Operation already in progress
errno.115 is: Operation now in progress
errno.116 is: Stale file handle
errno.117 is: Structure needs cleaning
errno.118 is: Not a XENIX named type file
errno.119 is: No XENIX semaphores available
errno.120 is: Is a named type file
errno.121 is: Remote I/O error
errno.122 is: Disk quota exceeded
errno.123 is: No medium found
errno.124 is: Wrong medium type
errno.125 is: Operation canceled
errno.126 is: Required key not available
errno.127 is: Key has expired
errno.128 is: Key has been revoked
errno.129 is: Key was rejected by service
errno.130 is: Owner died
errno.131 is: State not recoverable
errno.132 is: Operation not possible due to RF-kill
errno.133 is: Memory page has hardware error
