Linux system function return value and its programming application

In Linux programming, the return value of the system function is very important for the correct operation and error handling of the program. This article will introduce in detail the meaning of Linux system function return values ​​and how to apply these return values ​​in programming.

1. The meaning of the return value
   Linux system functions usually return an integer value as a sign of the function execution result. This return value can tell us whether the function executed successfully and what errors occurred. Generally, a return value of 0 indicates that the function executed successfully, while other non-zero values ​​indicate that the function failed to execute or an error occurred.

2. Error code
   When a system function returns a non-zero value, we can obtain the specific error code by looking for the manual page (man page) or related documentation of the function. These error codes can provide more detailed information to help us locate and solve the problem.

3. errno variable
   In Linux programming, errno is a global variable used to store the error code of the latest system call. We can access the errno variable by including the header file <errno.h>. When the system function returns a non-zero value, we can obtain detailed error information by checking the value of the errno variable.

The following is a sample program that demonstrates how to use the return value of the system function and the errno variable to handle errors:

#include <stdio.h>
#include