**errno** is a `global` variable in C that is defined in the `<errno.h>` header.

Although C does not provide direct support for exception handling, `errno` can be used for a similar purpose.



# Properties

When an error occurs, the errno variable is automatically assigned a code. This code can then be used to identify the error that has occurred.

Below is a list of some `errno` codes and their meanings:

Errno codes & meanings

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

int main(){

  //We are trying to open a file that does not exist
  FILE* input = fopen("NoFile.txt", "r");

  //Note the value in errno
  printf("\nError Code: %d\n", errno);

  //Print associated error message
  perror("Error Message");

  return 0;
}

In the above code, we tried to open a file that does not exist; so, the `errno` variable was assigned *error code* `2 : No such file or directory`.

What is errno in C?

errno is a global variable in C used to identify errors via specific codes, defined in <errno.h>.

Error Code	Meaning
1	Operation not permitted
2	No such file or directory
3	No such process
4	Interrupted system call
5	Input/Output error
6	No such device or address
7	Argument list too long
8	Exec format error
9	Bad file number
10	No child processes