Process.spawn
static VALUE
rb_f_spawn(int argc, VALUE *argv, VALUE _)
{
rb_pid_t pid;
char errmsg[CHILD_ERRMSG_BUFLEN] = { '\0' };
VALUE execarg_obj, fail_str;
struct rb_execarg *eargp;
execarg_obj = rb_execarg_new(argc, argv, TRUE, FALSE);
eargp = rb_execarg_get(execarg_obj);
fail_str = eargp->use_shell ? eargp->invoke.sh.shell_script : eargp->invoke.cmd.command_name;
pid = rb_execarg_spawn(execarg_obj, errmsg, sizeof(errmsg));
if (pid == -1) {
int err = errno;
rb_exec_fail(eargp, err, errmsg);
RB_GC_GUARD(execarg_obj);
rb_syserr_fail_str(err, fail_str);
}
#if defined(HAVE_WORKING_FORK) || defined(HAVE_SPAWNV)
return PIDT2NUM(pid);
#else
return Qnil;
#endif
}
Creates a new child process by doing one of the following in that process:
-
Passing string
command_lineto the shell. -
Invoking the executable at
exe_path.
This method has potential security vulnerabilities if called with untrusted input; see Command Injection.
Returns the process ID (pid) of the new process, without waiting for it to complete.
To avoid zombie processes, the parent process should call either:
-
Process.wait, to collect the termination statuses of its children. -
Process.detach, to register disinterest in their status.
The new process is created using the exec system call; it may inherit some of its environment from the calling program (possibly including open file descriptors).
Argument env, if given, is a hash that affects ENV for the new process; see Execution Environment.
Argument options is a hash of options for the new process; see Execution Options.
The first required argument is one of the following:
-
command_lineif it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more meta characters. -
exe_pathotherwise.
Argument command_line
String argument command_line is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:
spawn('if true; then echo "Foo"; fi') # => 798847 # Shell reserved word. Process.wait # => 798847 spawn('exit') # => 798848 # Built-in. Process.wait # => 798848 spawn('date > /tmp/date.tmp') # => 798879 # Contains meta character. Process.wait # => 798849 spawn('date > /nop/date.tmp') # => 798882 # Issues error message. Process.wait # => 798882
The command line may also contain arguments and options for the command:
spawn('echo "Foo"') # => 799031 Process.wait # => 799031
Output:
Foo
See Execution Shell for details about the shell.
Raises an exception if the new process could not execute.
Argument exe_path
Argument exe_path is one of the following:
-
The string path to an executable to be called.
-
A 2-element array containing the path to an executable to be called, and the string to be used as the name of the executing process.
Examplespawn('/usr/bin/date') # Path to date on Unix-style system. Process.wait
Output:
Mon Aug 28 11:43:10 AM CDT 2023
Ruby invokes the executable directly. This form does not use the shell; see Arguments args for caveats.
If one or more args is given, each is an argument or option to be passed to the executable:
spawn('echo', 'C*') # => 799392 Process.wait # => 799392 spawn('echo', 'hello', 'world') # => 799393 Process.wait # => 799393
Output:
C* hello world
Raises an exception if the new process could not execute.