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Standard names of such functions in C are execl, execle, execlp, execv, execve, and execvp (see below), but not "exec" itself. The Linux kernel has one corresponding system call named "execve", whereas all aforementioned functions are user-space wrappers around it.
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.
In Unix, the loader is the handler for the system call execve(). [1] The Unix loader's tasks include: validation (permissions, memory requirements etc.); memory-mapping the executable object from the disk into main memory; copying the command-line arguments into virtual memory; initializing registers (e.g., the stack pointer);
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.
a.out is a file format used in older versions of Unix-like computer operating systems for executables, object code, and, in later systems, shared libraries.This is an abbreviated form of "assembler output", the filename of the output of Ken Thompson's PDP-7 assembler. [1]
This is a list of POSIX (Portable Operating System Interface) commands as specified by IEEE Std 1003.1-2024, which is part of the Single UNIX Specification (SUS). These commands can be found on Unix operating systems and most Unix-like operating systems.
Kernel support for interpreter directives spread to other versions of Unix, and one modern implementation can be seen in the Linux kernel source in fs/binfmt_script.c. [30] This mechanism allows scripts to be used in virtually any context normal compiled programs can be, including as full system programs, and even as interpreters of other scripts.
The fork and execve functions in glibc are examples of this. They call the lower-level fork and execve system calls, respectively. This may lead to incorrectly using the terms "system call" and "syscall" to refer to higher-level library calls rather than the similarly named system calls, which they wrap. [4] [5]