I am writing an application that spawns a child process and interacts with
it via STDIN/STDOUT/STDERR through the life of the program.
When I run my script (the one that Node.JS spawns) from the terminal, it
waits for user input, as expected. In addition, if I write a short C
script that spawns the process via *execvp* (the same way that Node seems
to do it under the hood), the program waits for user input. However, when
I use Node's API, the process is killed soon after it is created, perhaps
when it starts waiting for input. Consider the code:
var spawn = require("child_process").spawn;
var shell = spawn("./run_shell.sh");
// Write the child's STDOUT to the main STDOUT
shell.stdout.on("data", function(data){
console.log(data.toString("utf8"));
});
// Listen for the exit event
shell.on("exit", function(code){
console.log("Exited with code "+code);
});
// Detect signals on the child process (for debugging)
var allSignals = ["SIGHUP", "SIGINT", "SIGQUIT", "SIGILL", "SIGABRT",
"SIGFPE", "SIGKILL", "SIGSEGV", "SIGPIPE", "SIGALRM", "SIGTERM", "SIGUSR1",
"SIGUSR2", "SIGCHLD", "SIGCONT", "SIGSTOP", "SIGTSTP", "SIGTTIN",
"SIGTTOU", "SIGBUS", "SIGPOLL", "SIGPROF", "SIGSYS", "SIGTRAP", "SIGURG",
"SIGVTALRM", "SIGXCPU", "SIGXFSZ", "SIGIOT", "SIGEMT", "SIGSTKFLT",
"SIGIO", "SIGCLD", "SIGPWR", "SIGINFO", "SIGLOST", "SIGWINCH", "SIGUNUSED"];
for(var i=allSignals.length-1; i>=0; i--){
var signal = allSignals[i];
shell.on(signal, (function(signal){
return function(){ console.log(signal+" received by child"); };
})(signal));
}
When I run the above application, all I get is the lines of my *run_shell.sh
* before that script starts waiting for STDIN, and then a "Exited with code
0". No signals are detected.
This behavior is *not* exhibited with *all* programs that wait for input on
STDIN.
It it is important, my shell script involves the use of an SELinux sandbox,
and the issue is exhibited only when SELinux is in enforcing mode. (When
run outside of Node, the script works as expected regardless of whether
SELinux is running.)
When I run the application in debug mode, when the following line (in *
child_process.js*) is run, I can tell by monitoring the shell's process
that the script starts and exits, even when the debugger keeps Node paused:
*915 var r = this._handle.spawn(options);
The debugger won't let me step inside that method. I assume this is
because that particular method is an entrypoint into the C++ backend of
Node.
What might be causing Node to kill the process? How could I go about
debugging to find out what part of Node is the culprit? Thanks!
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