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How does the shell use fork and exec?
exec will replace the contents of the currently running process with the information from a program binary. Thus the process the shell follows when launching a new program is to firstly fork , creating a new process, and then exec (i.e. load into memory and execute) the program binary it is supposed to run.
What is difference between fork and exec?
The fork() returns the PID of the child process. So the main difference between fork() and exec() is that fork starts new process which is a copy of the main process. the exec() replaces the current process image with new one, Both parent and child processes are executed simultaneously.
Why is fork a system call?
System call fork() is used to create processes. It takes no arguments and returns a process ID. The purpose of fork() is to create a new process, which becomes the child process of the caller. After a new child process is created, both processes will execute the next instruction following the fork() system call.
What is the difference between Fork ( ) and exec ( )?
On success, the PID of the child process is returned in the parent, and 0 is returned in the child. On failure, -1 is returned in the parent, no child process is created, and errno is set appropriately. The exec () family of functions replaces the current process image with a new process image.
How to fork and Exec a program in Linux?
The parent would fork a child process and the latter would exec the child program in it. The parent would wait for the child to do its work and terminate. $ # compile parent $ gcc parent.c -o parent $ #compile child $ gcc child.c -o child $ # run parent (and child) $ ./parent Parent: Hello, World! Parent: Waiting for Child to complete.
Which is the parent process fork or EXEC?
The shell is the parent process. It reads each line of input from the command line, forks a child shell process, which in turn exec’s the command. The shell parent process waits for the child to complete and then prompts for the next command. We were unable to load Disqus.
What happens when a process makes a fork system call?
When a process makes the fork system call, a new process is created which is a clone of the calling process. The code, data and the stack of the new process is copied from the calling process. The newly created process is called the child process, whereas the calling process is termed the parent process.