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The exec calls named ending with an e alter the environment for the new process image by passing a list of environment settings through the envp argument. This argument is an array of character pointers; each element (except for the final element) points to a null-terminated string defining an environment variable .
The actual system call does transfer control to the kernel (and is more implementation-dependent and platform-dependent than the library call abstracting it). For example, in Unix-like systems, fork and execve are C library functions that in turn execute instructions that invoke the fork and exec system calls.
For a process to start the execution of a different program, it first forks to create a copy of itself. Then, the copy, called the "child process", calls the exec system call to overlay itself with the other program: it ceases execution of its former program in favor of the other. The fork operation creates a separate address space for the ...
fork() is the name of the system call that the parent process uses to "divide" itself ("fork") into two identical processes. After calling fork(), the created child process is an exact copy of the parent except for the return value of the fork() call. This includes open files, register state, and all memory allocations, which includes the ...
In Unix (and in Unix-like operating systems), the exec() system call is used to perform chain loading. The program image of the current process is replaced with an entirely new image, and the current thread begins execution of that image. The common data area comprises the process' environment variables, which are preserved across the system call.
The wait system call is commonly invoked in the SIGCHLD handler. POSIX.1-2001 allows a parent process to elect for the kernel to automatically reap child processes that terminate by explicitly setting the disposition of SIGCHLD to SIG_IGN (although ignore is the default, automatic reaping only occurs if the disposition is set to ignore ...
As the final step of termination, a primitive system exit call is invoked, informing the operating system that the process has terminated and allows it to reclaim the resources used by the process. It is sometimes possible to bypass the usual cleanup; C99 offers the _exit() function which terminates the current process without any extra program ...
exec (system call), an operating system function for running a program; eval, a programming language function for executing a statement or evaluating an expression, variously called exec or eval; Exec (Amiga), the OS kernel of Amiga computers; CMS EXEC, an interpreted command procedure control language for IBM's VM/CMS operating system