Exec (system call)

In computing, exec is a functionality of an operating system that runs an executable file in the context of an already existing process, replacing the previous executable. This act is also referred to as an overlay. It is especially important in Unix-like systems, although it also exists elsewhere. As no new process is created, the process identifier (PID) does not change, but the machine code, data, heap, and stack of the process are replaced by those of the new program.

This article is about the computer operating system function. For other uses, see Exec (disambiguation). For the programming language function that executes a statement, see eval.

The exec call is available for many programming languages including compilable languages and some scripting languages. In OS command interpreters, the exec built-in command replaces the shell process with the specified program.

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