<errno.h>        -        Errors

If this header is included in a program, hen it is possible to detect whether an error has occurred during calls to certain library functions. After an error occurs the system variable erno will contain information about the error. The following symbolic constants are defined in the header file <errno.h> in response to either the DOS or UNIX error codes.

Jump to: demonstrate header <errno.h>

/* DOS Error Codes */

Number	Function	Description
0	EZERO	no Error
1	EINVFM	invalid function code
2	ENOENT	file not found
3	ENOPATH	path not found
4	EMFILE	too many open files
5	EACCES	access denied
6	EBADF	invalid handle
7	E2BIG	memory blocks destroyed
8	ENOMEM	insufficient memory
9	ENVMEM	invalid memory block address
10	EINVENV	invalid environment
11	EINVFMT	invlalid format
12	EINVACC	invalid acces code
13	EINVDAT	invalid data
15	ENODEV	invalid drive
16	ECURDIR	attempt to remove CurDir
17	ENOTSAM	not same devide
18	ENMFILE	no more files

/* RTL Error Codes */

19	EINVAL	invalid argument
20	ENOTDIR	not directory
21	EISDIR	is directory
22	ENOEXEC	corrupt exec file
32	EMLINK	cross-device link
33	EDOM	math argument
34	ERANGE	result too large
36	EDEADLOCK	file locking deadlock
80	EEXIST	dile exists MSDOS 3.0+
-1	EFAULT	unknown error
-1	EPERM	UNIX - not in MSDOS
-1	ESRCH	UNIX -not in MSDOS
-1	EINTR	UNIX - not in MSDOS
-1	EIO	UNIX - not in MSDOS
-1	ENXIO	UNIX - not in MSDOS
-1	ECHILD	UNIX - not in MSDOS
-1	EAGAIN	UNIX - not in MSDOS
-1	ENOTBLK	UNIX - not in MSDOS
-1	EBUSY	UNIX - not in MSDOS
-1	ENFILE	UNIX - not in MSDOS
-1	ENOTTY	UNIX - not in MSDOS
-1	ETXTBSY	UNIX - not in MSDOS
-1	EFBIG	UNIX - not in MSDOS
-1	ENOTSPC	UNIX - not in MSDOS
-1	ESPIPE	UNIX - not in MSDOS
-1	EROFS	UNIX - not in MSDOS
-1	EPIPE	UNIX - not in MSDOS
-1	EUCLEAN	UNIX - not in MSDOS

Program to demonstrate header <errno.h> :

#include <stdio.h>
#include <errno.h>
#include <math.h>
#include <limits.h>

int man(void)
{

    printf("%10.2G\n", sqrt(-1.0);
    printf("%d\n", errno);
    printf("%10.2G\n", exp(INF_MAX));
    printf("%d\n", errno);

    return 0;

}

Results from program:

0
33
1.8E+308
34

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