This tag refers to the starting of another, subsidiary program. It is named after the family of POSIX system calls whose name starts with “exec” (notably “execve”) though similar concepts exist on other platforms as well, especially when combined with the starting up of another process.
From The Open Group Base Specifications Issue 7
The exec family of functions shall replace the current process image with a new process image. The new image shall be constructed from a regular, executable file called the new process image file. There shall be no return from a successful exec, because the calling process image is overlaid by the new process image.
This tag is commonly used with php when it refers to execute an external program within a php code.
Examples
echo exec('whoami');
References
- The Open Group Base Specifications Issue 7 http://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html
- Wikipedia entry https://en.wikipedia.org/wiki/Exec_%28operating_system%29
- php.net on exec() function
