errno
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Header File
errno.h
Syntax
extern int errno;
Description
errno is used by perror to print error messages when certain library routines fail to accomplish their appointed tasks.
When an error in a math or system call occurs, errno is set to indicate the type of error. Sometimes errno and _doserrno are equivalent. At other times, errno does not contain the actual operating system error code, which is contained in _doserrno. Still other errors might occur that set only errno, not _doserrno.
Example
#include <errno.h> #include <stdio.h> int main() { int i = 0; // Global value _sys_nerr also defined in errno.h while(i < _sys_nerr) { printf("%s\n", _sys_errlist[i]); i++; } return 0; }