□ Global variable that stores the cause of a error when a function is executed
□ Return value can only check whether an error occurred
□ If there is no error, 0 is stored. If there is a error, error code is stored
□ Error code is stored in the path /usr/include/asm/errno.h
□ #include is needed to use errno variable
It is also posted at : http://cysecguide.blogspot.com/2016/09/errno-variable.html