Show ERRNO and Value
Tags: linux, shell, bash
Published: 2023-05-05 05:55:17

I think there are times when I want to know the value of ERRNO when I build a program, or when I want to know the error message corresponding to the value, such as an error message of some command.
At times like that, I check with a simple shell script I made N years ago.

- I don't think about difficult things such as whether it works in any environment or whether all errno can be checked (just think about it when it doesn't work).
- For the time being, I moved in an environment where gcc is installed in Linux.
- It just grep the include file for C language.

## `errno.sh`

The created `errno.sh` script is as follows.

```shell
#!/bin/bash

if [[ $# -ne 1 || "$1" = "-h" || "$1" = "--help" ]]; then
  echo "Usage: $(basename $0) { ERROR_NUMBER | ERROR_NAME }" >&2
  exit 1

elif [[ ! ( "$1" =~ ^E[A-Z0-9]+$ || "$1" =~ ^[1-9][0-9]*$ ) ]]; then
  echo "illegal argument." >&2
  exit 1

elif ! find /usr/include -name 'errno*.h' -print0 |
  xargs -0 -r grep -Eh \
    -e "^\\s*#\\s*define\\s+E[A-Z0-9]+\\s+$1\\>" \
    -e "^\\s*#\\s*define\\s+$1\\s+[1-9][0-9]*\\>" \
    -e "^\\s*#\\s*define\\s+$1\\s+E[A-Z0-9]+\\>"
then
  echo "errno not found($1)." >&2
  exit 1
fi
```

Some examples are shown below.

```
$ errno.sh
Usage: errno.sh { ERROR_NUMBER | ERROR_NAME }
$ errno.sh EIO
#define EIO              5      /* I/O error */
$ errno.sh 125
#define ECANCELED       125     /* Operation Canceled */
```

## note

### ERRNO range

```
$ for N in $(seq 1 140) ; do errno.sh $N ; done
#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 EDOM   33      /* Math argument out of domain of function.  */
#define ERANGE          34      /* Math result not representable */
# define ERANGE 34      /* Math result not representable.  */
#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 */
errno not found(41).
#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 */
errno not found(58).
#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 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 ECANCELED     125
#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 */
#define EOWNERDEAD      130     /* Owner died */
#  define EOWNERDEAD            130
#define ENOTRECOVERABLE 131     /* State not recoverable */
#  define ENOTRECOVERABLE       131
#define ERFKILL         132     /* Operation not possible due to RF-kill */
#  define ERFKILL               132
#define EHWPOISON       133     /* Memory page has hardware error */
#  define EHWPOISON             133
errno not found(134).
errno not found(135).
errno not found(136).
errno not found(137).
errno not found(138).
errno not found(139).
errno not found(140).
$ 
```

### ERRNO with multiple names

```
$ errno.sh EDEADLK
#define EDEADLK         35      /* Resource deadlock would occur */
#define EDEADLOCK       EDEADLK
$ errno.sh EAGAIN
#define EAGAIN          11      /* Try again */
#define EWOULDBLOCK     EAGAIN  /* Operation would block */
$ errno.sh EOPNOTSUPP
#define EOPNOTSUPP      95      /* Operation not supported on transport endpoint */
# define ENOTSUP EOPNOTSUPP
```