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)