Host 2!:

2!:0 y Host. list y is executed by host system, and result is returned. 例如, 2!:0 'dir *.exe'. Not available for 視窗 or 麥金塔.
2!:1 y Spawn. Like 2!:0, but 得到 '' without waiting for host to finish. Any output is ignored. 例如, 2!:1 can be used to invoke a text-editor. Not available for 視窗 or 麥金塔.
2!:2 y Host IO. (Unix only.) host 指令行 y is passed to /bin/sh for processing, connecting two file numbers to command's standard input與output. result is a 3-分子 list of process id of task started與 file numbers associated with its standard input與output. se file numbers also appear 在result of 1!:20. In this case, instead of appearing with a name y appear with 指令行, prefixed by > (standard input) or < (standard output). files associated with process should be closed with 1!:22 when no longer in use. See also 2!:3 for 動詞 to wait for processes to complete.
2!:3 y Wait. (Unix only.) Wait for process id y to terminate. result is status code returned by process.
2!:4 y 指令行. When J is used as a shell, result of 2!:4 is a boxed list representing 指令行. first 分子 is name of shell script itself; subsequent 分子 are 引數, if any.
2!:5 y Getenv. value of shell environment variable named y.If named variable is undefined, result is 0.
2!:55 y Terminate Session. y is an 整數 return code