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(7) 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(7),
standards(7) December 14, 2006 SYSTEM(3C)
