Gets a system error message (strerror) or prints a user-supplied error message (_strerror).
| #include <string.h> | Required only for function declarations |
char *strerror( int errnum );
char *_strerror( char *string );
| errnum | Error number | |
| string | User-supplied message |
The strerror function maps errnum to an error-message string, returning a pointer to the string. The function itself does not actually print the message; for that, you need to call an output function such as fprintf:
if (( _access( "datafile",2 )) == -1 )
fprintf( stderr, strerror(NULL) );
If string is passed as NULL, _strerror returns a pointer to a string containing the system error message for the last library call that produced an error. The error-message string is terminated by the newline character ('\n').
If string is not equal to NULL, then _strerror returns a pointer to a string containing (in order) your string message, a colon, a space, the system error message for the last library call producing an error, and a newline character. Your string message can be a maximum of 94 bytes long.
Unlike perror, _strerror alone does not print any messages. To print the message returned by _strerror to stderr, your program will need an fprintf statement, as shown in the following lines:
if (( _access( "datafile",2 )) == -1 )
fprintf( stderr, _strerror(NULL) );
The actual error number for _strerror is stored in the variable errno. The system error messages are accessed through the variable sys_errlist, which is an array of messages ordered by error number. The _strerror function accesses the appropriate error message by using the errno value as an index to the variable sys_errlist. The value of the variable sys_nerr is defined as the maximum number of elements in the sys_errlist array.
To produce accurate results, _strerror should be called immediately after a library routine returns with an error. Otherwise, the errno value may be overwritten by subsequent calls.
Note that the _strerror function under Microsoft C version 5.0 is identical to
the version 4.0 strerror function. The name was altered to permit the inclusion
in Microsoft C version 5.0 of the ANSI-conforming strerror function. The
_strerror function is not part of the ANSI definition but is instead a Microsoft extension to it; it should not be used where portability is desired. For ANSI compatibility, use strerror instead.
The strerror and _strerror functions return a pointer to the error-message string. The string can be overwritten by subsequent calls to strerror or _strerror, respectively.
strerror
Standards:ANSI
16-Bit:DOS, QWIN, WIN, WIN DLL
32-Bit:DOS32X
_strerror
Standards:None
16-Bit:DOS, QWIN, WIN, WIN DLL
32-Bit:DOS32X
See the example for perror.