NodeOS-boot-multiuser> help
ReferenceError: help is not defined
    at repl:1:1
    at ContextifyScript.Script.runInContext (vm.js:35:29)
    at REPLServer.defaultEval (repl.js:348:29)
    at bound (domain.js:280:14)
    at REPLServer.runBound [as eval] (domain.js:293:12)
    at REPLServer.<anonymous> (repl.js:545:10)
    at emitOne (events.js:96:13)
    at REPLServer.emit (events.js:188:7)
    at REPLServer.Interface._onLine (readline.js:239:10)
    at REPLServer.Interface._line (readline.js:585:8)

zar@delta in ~
→ ./test.sh
ls: 10: No such file or directory
zar@delta in ~
→ cat test.sh
#!/usr/bin/dash
ls /proc/self/fd 3>/dev/null 4>/dev/null 5>/dev/null 6>/dev/null 7>/dev/null 8>/dev/null 9>/dev/null 10>/dev/null

Open files are represented by decimal numbers starting with zero. The largest possible value is implementation-defined; however, all implementations shall support at least 0 to 9, inclusive, for use by the application. These numbers are called "file descriptors". The values 0, 1, and 2 have special meaning and conventional uses and are implied by certain redirection operations; they are referred to as standard input, standard output, and standard error, respectively. Programs usually take their input from standard input, and write output on standard output. Error messages are usually written on standard error. The redirection operators can be preceded by one or more digits (with no intervening <blank> characters allowed) to designate the file descriptor number.