forkexecve

The function forkexecve is a convenience routine provided in some Unix‑like operating systems to combine the typical sequence of creating a new process and executing a program in a single call. It is defined in <stdlib.h> or a system dependent header and returns the process ID of the child to the parent, or –1 on error. The prototype is

int forkexecve(const char path, char const argv[], char const envp[]);

Under the covers forkexecve performs a fork followed by an execve in the child process. If execve() succeeds the child replaces its address space with the new program; otherwise it terminates with a failure status. The parent receives the child’s process ID and can manage it as with a standard fork.

The routine is intended to simplify common patterns such as launching a helper program or daemon. It differs from the two‑step sequence in that it guarantees the child executes the target program before the parent can observe the new process, reducing race conditions. However, it is not part of the POSIX standard and may be unavailable on some platforms, such as recent Linux kernels. Portable code should use explicit fork() and execve() pairs instead.

When forkexecve fails the return value is –1 and errno is set to the same value that would result from a fork or execve failure. Because forkexecve performs both operations atomically, a failure from either step makes the entire call fail. Proper error handling therefore checks the return value before attempting to wait for the child.

In practice, services that need to spawn subsystems—such as web servers launching CGI scripts or database servers starting child workers—have historically used forkexecve for brevity. Modern codebases increasingly replace it with signal‑safe wrappers around fork() and execve() to maintain portability and control over the environment passed to the new process.