Question

explain the use of fork, exec, and wait functions in unix

Answer 1

In this article, can|we'll|we are going to} start from alittle clarification of method IDs so we'll quickly get on to the sensible aspects where-in we have a tendency to will discuss some method connected C functions like fork(), execv() and wait() .

The fork() Function

As already discussed in the article making a daemon method in C, the fork function is used to form a method from inside a method.

The resultant new method created by fork() is best-known as kid method whereas the initial method (from that fork() was called) becomes the parent process.

The function fork() is referred to as once (in the parent process) however it returns double. Once it returns within the parent method whereas the second time it returns in the kid process. Note that the order of execution of the parent and the child might vary relying upon the method programming rule. So we have a tendency to see that fork perform is used in method creation.

The signature of fork() is :

pid_t fork(void);

Another set of functions that are typically used for making a method is the EXEC family of functions. These functions are in the main used wherever there is a demand of running Associate in Nursing existing binary from withing a method.

For example, suppose we wish to run the ‘whoami’ command from inside a method, then in these kind of scenarios the exec() perform or alternative members of this family is employed. A point price noting here is that with a decision to any of the EXEC family of functions, the current method image is replaced by a brand new process image.

A common member of this family is that the execv() function. Its signature is :

int execv(const char *path, char *const argv[]);

There are bound things wherever once a kid method terminates or amendments state then the parent method ought to return to grasp concerning the change of the state or termination standing of the kid method. In that case functions like wait() are employed by the parent method wherever the parent will question the amendment in state of the kid method victimization these functions.

The signature of wait() is :

pid_t wait(int *status);