The easy way to run another program is to use the system
function. This function does all the work of running a subprogram, but
it doesn't give you much control over the details: you have to wait
until the subprogram terminates before you can do anything else.
This function executes command as a shell command. In the GNU C Library, it always uses the default shell
shto run the command. In particular, it searches the directories inPATHto find programs to execute. The return value is-1if it wasn't possible to create the shell process, and otherwise is the status of the shell process. See Process Completion, for details on how this status code can be interpreted.If the command argument is a null pointer, a return value of zero indicates that no command processor is available.
This function is a cancellation point in multi-threaded programs. This is a problem if the thread allocates some resources (like memory, file descriptors, semaphores or whatever) at the time
systemis called. If the thread gets canceled these resources stay allocated until the program ends. To avoid this calls tosystemshould be protected using cancellation handlers.The
systemfunction is declared in the header file stdlib.h.
Portability Note: Some C implementations may not have any
notion of a command processor that can execute other programs. You can
determine whether a command processor exists by executing
system (NULL); if the return value is nonzero, a command
processor is available.
The popen and pclose functions (see Pipe to a Subprocess) are closely related to the system function. They
allow the parent process to communicate with the standard input and
output channels of the command being executed.