SYSTEM(3C) Standard C Library Functions SYSTEM(3C)


NAME


system - issue a shell command

SYNOPSIS


#include <stdlib.h>

int system(const char *string);


DESCRIPTION


The system() function causes string to be given to the shell as input, as
if string had been typed as a command at a terminal. The invoker waits
until the shell has completed, then returns the exit status of the shell
in the format specified by waitpid(3C).


If string is a null pointer, system() checks if the shell exists and is
executable. If the shell is available, system() returns a non-zero
value; otherwise, it returns 0.


The system() function sets the SIGINT and SIGQUIT signals to be ignored,
and blocks the SIGCHLD signal for the calling thread, while waiting for
the command to terminate. The system() function does not affect the
termination status of any child of the calling processes other than the
process it creates.


The termination status of the process created by the system() function is
not affected by the actions of other threads in the calling process (it
is invisible to wait(3C)) or by the disposition of the SIGCHLD signal in
the calling process, even if it is set to be ignored. No SIGCHLD signal
is sent to the process containing the calling thread when the command
terminates.

RETURN VALUES


The system() function executes posix_spawn(3C) to create a child process
running the shell that in turn executes the commands in string. If
posix_spawn() fails, system() returns -1 and sets errno to indicate the
error; otherwise the exit status of the shell is returned.

ERRORS


The system() function may set errno values as described by fork(2), in
particular:

EAGAIN
A resource control or limit on the total number of processes,
tasks or LWPs under execution by a single user, task,
project, or zone has been exceeded, or the total amount of
system memory available is temporarily insufficient to
duplicate this process.


ENOMEM
There is not enough swap space.


EPERM
The {PRIV_PROC_FORK} privilege is not asserted in the
effective set of the calling process.


USAGE


The system() function manipulates the signal handlers for SIGINT and
SIGQUIT. It is therefore not safe to call system() in a multithreaded
process, since some other thread that manipulates these signal handlers
and a thread that concurrently calls system() can interfere with each
other in a destructive manner. If, however, no such other thread is
active, system() can safely be called concurrently from multiple threads.
See popen(3C) for an alternative to system() that is thread-safe.

ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | Unsafe |
+--------------------+-----------------+

SEE ALSO


ksh(1), sh(1), popen(3C), posix_spawn(3C), wait(3C), waitpid(3C),
attributes(5), standards(5)


December 14, 2006 SYSTEM(3C)