The easy way to run another program is to use the
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.
Preliminary: | MT-Safe | AS-Unsafe plugin heap lock | AC-Unsafe lock mem | See POSIX Safety Concepts.
This function executes command as a shell command. In the GNU C Library,
it always uses the default shell
sh to run the command.
In particular, it searches the directories in
PATH to find
programs to execute. The return value is
-1 if 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
called. If the thread gets canceled these resources stay allocated
until the program ends. To avoid this calls to
system should be
protected using cancellation handlers.
system function is declared in the header file
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.
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.