The pedantic answer to your question is no. The only system call that creates a new process is fork. The system call underlying execvp (called execve) loads a new program into an existing process, which is a different thing.

Some species of Unix have additional system calls besides fork (e.g. vfork, rfork, clone) that create a new process, but they are only small variations on fork itself, and none of them are part of the POSIX standard that specifies the functionality you can count on on anything that calls itself a Unix.

The slightly more helpful answer is that you might be looking for posix_spawn, which is a library routine wrapping fork and exec into a single operation, but I find it more troublesome to use that correctly than to write my own fork+exec subroutine. YMMV.

posix_spawn is the only posix compliant way to create a child process without calling fork directly. I say 'directly' because historically posix_spawn would itself just call fork, or vfork. However, that is no longer the case in GNU/linux. posix_spawn itself may be more efficient than fork, in addition to perhaps being a stronger fit conceptually when code is attempting to run a different executable.

If you aren't worried about portability, you can abandon posix and couple yourself directly to the kernel you are targeting. On linux the system call to create a child process is clone. At the time of this answer the manual page provides documentation for three variants, including the relatively new clone3.

I believe you can take the example from the manual page and add an execvp call to childFunc. I have not tried it yet, though!

Unlike Windows systems, where creating a new process and executing a new process image happen in a single step, Linux and other UNIX-like systems do them as two distinct steps.

The fork function makes an exact duplicate of the calling process and actually returns twice, once to the parent process and once to the child process. The execvp function (and other functions in the exec family) executes a new process image in the same process, overwriting the existing process image.

You can call execvp without calling fork first. If so, that just means the currently running program goes away and is replaced with the given program. However, fork is the way to create a new process.

As user zwol has already explained, execve() does not fork a new process. Rather, it replaces the address space and CPU state of current process, loads the new address space from the executable filename and starts it from main() with argument list argv and environment variable list envp. It keeps pid and open files.

int execve(const char *filename,char *const argv [],char *const envp[]);

filename: name of executable file to run
argv: Command line arguments
envp: environment variable settings (e.g., $PATH, $HOME, etc.)

posix_spawn. But it ignores failures of execvp() -- potentially because implementing this was regarded as too complicated.