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Re: [RFC] Patch implementing EXECUTE_COMMAND_LINE
Gerald Pfeifer wrote:
> On Sun, 17 May 2009, Steve Kargl wrote:
>> Are you sure that this is asynchronous? FreeBSD's manpage
>> indicates that system(3) is synchronous.
>> man 3 system
>> The system() function hands the argument string to the command inter-
>> preter sh(1). The calling process waits for the shell to finish execut-
>> ing the command, ignoring SIGINT and SIGQUIT, and blocking SIGCHLD.
> Same on GNU/Linux with glibc:
> system() executes a command specified in command by calling /bin/sh -c
> command, and returns after the command has been completed. During exe-
> cution of the command, SIGCHLD will be blocked, and SIGINT and SIGQUIT
> will be ignored.
Which is not too surprising as POSIX (IEEE Std 1003.1-2001) has the same:
> If command is a null pointer, the system() function shall
> determine whether the host environment has a
> command processor. If command is not a null pointer, the
> system() function shall pass the string pointed
> to by command to that command processor to be executed in an
> implementation-defined manner; this might
> then cause the program calling system() to behave in a
> non-conforming manner or to terminate.
> The environment of the executed command shall be as if a child
> process were created using fork(), and the
> child process invoked the sh utility using execl() as follows:
> execl(<shell path>, "sh", "-c", command, (char *)0);
> where <shell path> is an unspecified pathname for the sh utility.
> The system() function shall ignore the SIGINT and SIGQUIT
> signals, and shall block the SIGCHLD signal,
> while waiting for the command to terminate. If this might cause
> the application to miss a signal that
> would have killed it, then the application should examine the
> return value from system() and take what-
> ever action is appropriate to the application if the command
> terminated due to receipt of a signal.
> The system() function shall not affect the termination status
> of any child of the calling processes other
> than the process or processes it itself creates.
> The system() function shall not return until the child process
> has terminated.
For Windows: "system" there calls "cmd.exe", see: