Check out example codes for "ruby fork self service". It will help you in understanding the concepts better.
Code Example 1
env: hash name => val : set the environment variable name => nil : unset the environment variable the keys and the values except for +nil+ must be strings. command...: commandline : command line string which is passed to the standard shell cmdname, arg1, ... : command name and one or more arguments (This form does not use the shell. See below for caveats.) [cmdname, argv0], arg1, ... : command name, argv and zero or more arguments (no shell) options: hash clearing environment variables: :unsetenv_others => true : clear environment variables except specified by env :unsetenv_others => false : don't clear (default) process group: :pgroup => true or 0 : make a new process group :pgroup => pgid : join the specified process group :pgroup => nil : don't change the process group (default) create new process group: Windows only :new_pgroup => true : the new process is the root process of a new process group :new_pgroup => false : don't create a new process group (default) resource limit: resourcename is core, cpu, data, etc. See Process.setrlimit. :rlimit_resourcename => limit :rlimit_resourcename => [cur_limit, max_limit] umask: :umask => int redirection: key: FD : single file descriptor in child process [FD, FD, ...] : multiple file descriptor in child process value: FD : redirect to the file descriptor in parent process string : redirect to file with open(string, "r" or "w") [string] : redirect to file with open(string, File::RDONLY) [string, open_mode] : redirect to file with open(string, open_mode, 0644) [string, open_mode, perm] : redirect to file with open(string, open_mode, perm) [:child, FD] : redirect to the redirected file descriptor :close : close the file descriptor in child process FD is one of follows :in : the file descriptor 0 which is the standard input :out : the file descriptor 1 which is the standard output :err : the file descriptor 2 which is the standard error integer : the file descriptor of specified the integer io : the file descriptor specified as io.fileno file descriptor inheritance: close non-redirected non-standard fds (3, 4, 5, ...) or not :close_others => false : inherit current directory: :chdir => str The 'cmdname, arg1, ...' form does not use the shell. However, on different OSes, different things are provided as built-in commands. An example of this is 'echo', which is a built-in on Windows, but is a normal program on Linux and Mac OS X. This means that `Process.spawn 'echo', '%Path%'` will display the contents of the `%Path%` environment variable on Windows, but `Process.spawn 'echo', '$PATH'` prints the literal '$PATH'.
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