手繰る手繰る include ファイルたち

CentOS7 の上で、"fgrep errno.h /usr/include -r" などと手繰っていくと…

/usr/include/errno.h
--> /usr/include/bits/errno.h [ENOTSUP=EOPNOTSUPP]
  --> /usr/include/linux/errno.h
    --> /usr/include/asm/errno.h
      --> /usr/include/asm-generic/errno.h [EDEADLK:35 - EHWPOISON:133]
        --> /usr/include/asm-generic/errno-base.h [EPERM:1 - ERANGE:34]

"[]" 内は、errnoの定義値の範囲。

けっこう深いところで定義されている。

定義一覧

/usr/include/asm-generic/errno-base.h

# define EPERM            1      /* Operation not permitted */
# define ENOENT           2      /* No such file or directory */
# define ESRCH            3      /* No such process */
# define EINTR            4      /* Interrupted system call */
# define EIO              5      /* I/O error */
# define ENXIO            6      /* No such device or address */
# define E2BIG            7      /* Argument list too long */
# define ENOEXEC          8      /* Exec format error */
# define EBADF            9      /* Bad file number */
# define ECHILD          10      /* No child processes */
# define EAGAIN          11      /* Try again */
# define ENOMEM          12      /* Out of memory */
# define EACCES          13      /* Permission denied */
# define EFAULT          14      /* Bad address */
# define ENOTBLK         15      /* Block device required */
# define EBUSY           16      /* Device or resource busy */
# define EEXIST          17      /* File exists */
# define EXDEV           18      /* Cross-device link */
# define ENODEV          19      /* No such device */
# define ENOTDIR         20      /* Not a directory */
# define EISDIR          21      /* Is a directory */
# define EINVAL          22      /* Invalid argument */
# define ENFILE          23      /* File table overflow */
# define EMFILE          24      /* Too many open files */
# define ENOTTY          25      /* Not a typewriter */
# define ETXTBSY         26      /* Text file busy */
# define EFBIG           27      /* File too large */
# define ENOSPC          28      /* No space left on device */
# define ESPIPE          29      /* Illegal seek */
# define EROFS           30      /* Read-only file system */
# define EMLINK          31      /* Too many links */
# define EPIPE           32      /* Broken pipe */
# define EDOM            33      /* Math argument out of domain of func */
# define ERANGE          34      /* Math result not representable */

/usr/include/asm-generic/errno.h

# define EDEADLK         35      /* Resource deadlock would occur */
# define ENAMETOOLONG    36      /* File name too long */
# define ENOLCK          37      /* No record locks available */
# define ENOSYS          38      /* Function not implemented */
# define ENOTEMPTY       39      /* Directory not empty */
# define ELOOP           40      /* Too many symbolic links encountered */
# define EWOULDBLOCK     EAGAIN  /* Operation would block */
# define ENOMSG          42      /* No message of desired type */
# define EIDRM           43      /* Identifier removed */
# define ECHRNG          44      /* Channel number out of range */
# define EL2NSYNC        45      /* Level 2 not synchronized */
# define EL3HLT          46      /* Level 3 halted */
# define EL3RST          47      /* Level 3 reset */
# define ELNRNG          48      /* Link number out of range */
# define EUNATCH         49      /* Protocol driver not attached */
# define ENOCSI          50      /* No CSI structure available */
# define EL2HLT          51      /* Level 2 halted */
# define EBADE           52      /* Invalid exchange */
# define EBADR           53      /* Invalid request descriptor */
# define EXFULL          54      /* Exchange full */
# define ENOANO          55      /* No anode */
# define EBADRQC         56      /* Invalid request code */
# define EBADSLT         57      /* Invalid slot */

# define EDEADLOCK       EDEADLK

# define EBFONT          59      /* Bad font file format */
# define ENOSTR          60      /* Device not a stream */
# define ENODATA         61      /* No data available */
# define ETIME           62      /* Timer expired */
# define ENOSR           63      /* Out of streams resources */
# define ENONET          64      /* Machine is not on the network */
# define ENOPKG          65      /* Package not installed */
# define EREMOTE         66      /* Object is remote */
# define ENOLINK         67      /* Link has been severed */
# define EADV            68      /* Advertise error */
# define ESRMNT          69      /* Srmount error */
# define ECOMM           70      /* Communication error on send */
# define EPROTO          71      /* Protocol error */
# define EMULTIHOP       72      /* Multihop attempted */
# define EDOTDOT         73      /* RFS specific error */
# define EBADMSG         74      /* Not a data message */
# define EOVERFLOW       75      /* Value too large for defined data type */
# define ENOTUNIQ        76      /* Name not unique on network */
# define EBADFD          77      /* File descriptor in bad state */
# define EREMCHG         78      /* Remote address changed */
# define ELIBACC         79      /* Can not access a needed shared library */
# define ELIBBAD         80      /* Accessing a corrupted shared library */
# define ELIBSCN         81      /* .lib section in a.out corrupted */
# define ELIBMAX         82      /* Attempting to link in too many shared libraries */
# define ELIBEXEC        83      /* Cannot exec a shared library directly */
# define EILSEQ          84      /* Illegal byte sequence */
# define ERESTART        85      /* Interrupted system call should be restarted */
# define ESTRPIPE        86      /* Streams pipe error */
# define EUSERS          87      /* Too many users */
# define ENOTSOCK        88      /* Socket operation on non-socket */
# define EDESTADDRREQ    89      /* Destination address required */
# define EMSGSIZE        90      /* Message too long */
# define EPROTOTYPE      91      /* Protocol wrong type for socket */
# define ENOPROTOOPT     92      /* Protocol not available */
# define EPROTONOSUPPORT 93      /* Protocol not supported */
# define ESOCKTNOSUPPORT 94      /* Socket type not supported */
# define EOPNOTSUPP      95      /* Operation not supported on transport endpoint */
# define EPFNOSUPPORT    96      /* Protocol family not supported */
# define EAFNOSUPPORT    97      /* Address family not supported by protocol */
# define EADDRINUSE      98      /* Address already in use */
# define EADDRNOTAVAIL   99      /* Cannot assign requested address */
# define ENETDOWN        100     /* Network is down */
# define ENETUNREACH     101     /* Network is unreachable */
# define ENETRESET       102     /* Network dropped connection because of reset */
# define ECONNABORTED    103     /* Software caused connection abort */
# define ECONNRESET      104     /* Connection reset by peer */
# define ENOBUFS         105     /* No buffer space available */
# define EISCONN         106     /* Transport endpoint is already connected */
# define ENOTCONN        107     /* Transport endpoint is not connected */
# define ESHUTDOWN       108     /* Cannot send after transport endpoint shutdown */
# define ETOOMANYREFS    109     /* Too many references: cannot splice */
# define ETIMEDOUT       110     /* Connection timed out */
# define ECONNREFUSED    111     /* Connection refused */
# define EHOSTDOWN       112     /* Host is down */
# define EHOSTUNREACH    113     /* No route to host */
# define EALREADY        114     /* Operation already in progress */
# define EINPROGRESS     115     /* Operation now in progress */
# define ESTALE          116     /* Stale file handle */
# define EUCLEAN         117     /* Structure needs cleaning */
# define ENOTNAM         118     /* Not a XENIX named type file */
# define ENAVAIL         119     /* No XENIX semaphores available */
# define EISNAM          120     /* Is a named type file */
# define EREMOTEIO       121     /* Remote I/O error */
# define EDQUOT          122     /* Quota exceeded */

# define ENOMEDIUM       123     /* No medium found */
# define EMEDIUMTYPE     124     /* Wrong medium type */
# define ECANCELED       125     /* Operation Canceled */
# define ENOKEY          126     /* Required key not available */
# define EKEYEXPIRED     127     /* Key has expired */
# define EKEYREVOKED     128     /* Key has been revoked */
# define EKEYREJECTED    129     /* Key was rejected by service */

/* for robust mutexes */
# define EOWNERDEAD      130     /* Owner died */
# define ENOTRECOVERABLE 131     /* State not recoverable */

# define ERFKILL         132     /* Operation not possible due to RF-kill */

# define EHWPOISON       133     /* Memory page has hardware error */

/usr/include/bits/errno.h

# define ENOTSUP EOPNOTSUPP

errno ってなに？（おまけ）

たとえばこんなコードが有るとして…

# include <stdio.h>
# include <string.h>

# include <sys/types.h>
# include <sys/stat.h>
# include <fcntl.h>

# include <errno.h>

# include <unistd.h>

int main(void)
{
    int fd = open("/x",O_RDWR|O_CREAT,0777);

    printf("fd = %d, errno=%d: %s\n", fd, errno, strerror(errno));

    if (fd!=-1) close(fd);
    return 0;
}

コンパイルして実行すると…

$ ./a.out
fd = -1, errno=13: Permission denied

この "13" は前述の include ファイルから EACCES と定義されていて "Permission denied" という意味になる。