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What does the exec () system call do?
The exec system call is used to execute a file which is residing in an active process. When exec is called the previous executable file is replaced and new file is executed. More precisely, we can say that using exec system call will replace the old file or program from the process with a new file or program.
Does exec terminate process?
1 Answer. The child process doesn’t exit when you exec . What happens is – the current process is replaced by whatever it’s exec ing. The exec() family of functions replaces the current process image with a new process image.
Does exec call exit?
The exec ‘d program’s exit status is sent back to the parent process that executed your shell. The only way that exec’s exit status can be interpreted by the line following exec is if the exec calls fails, normally only if the command requested does not exist or if the file is not executable.
Does Execve return?
execve() does not return on success, and the text, data, bss, and stack of the calling process are overwritten by that of the program loaded. The program invoked inherits the calling process’s PID, and any open file descriptors that are not set to close-on-exec.
What happens if you call exec without using fork ()?
A program that calls exec() without fork() is chain loading, overlaying its process with a different program image. There is a whole subculture of chain loading utilities that do particular things to process state and then execute another program to run with that revised process state.
Does exec change PID?
According to the documentation, an exec does not modify the pid of a process.
What is the difference between exec and fork?
fork vs exec fork starts a new process which is a copy of the one that calls it, while exec replaces the current process image with another (different) one. Both parent and child processes are executed simultaneously in case of fork() while Control never returns to the original program unless there is an exec() error.
What’s the major difference of fork and exec?
The main difference between fork and exec is that fork creates a new process while preserving the parent process, but exec creates a new process without preserving the parent process. A computer operates in two modes: the kernel mode and user mode.
Can you use exec without fork?
2 Answers. No, you cannot start another program and get back from it without fork(2) followed by some execve(2) code (which is what popen , posix_spawn , and system are doing).
Do I need to fork before exec?
Not really. After a fork, you already have new process, even not that much different from its parent. There are some cases where no exec need to follow a fork.