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instance method
IO#pid
pid → integer or nil
io.c
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static VALUE
rb_io_pid(VALUE io)
{
rb_io_t *fptr;
GetOpenFile(io, fptr);
if (!fptr->pid)
return Qnil;
return PIDT2NUM(fptr->pid);
}
Returns the process ID of a child process associated with the stream, which will have been set by IO#popen, or nil if the stream was not created by IO#popen:
Example
pipe = IO.popen("-") if pipe $stderr.puts "In parent, child pid is #{pipe.pid}" else $stderr.puts "In child, pid is #{$$}" end
Output:
In child, pid is 26209 In parent, child pid is 26209