# LispKit System Call

Library `(lispkit system call)` currently defines a single procedure `system-call` for invoking external binaries as a sub-process of the LispKit interpreter. This library is macOS-specific and requires careful usage in portable code.

(system-call path args) [procedure]
(system-call path args env)
(system-call path args env port)
(system-call path args env port input)

Executes the binary at path passing the string representation of the elements of list args as command-line arguments. env is an association list defining environment variables. Both keys and values are strings. The output generated by executing the binary is directed towards port, which is a textual output port. The default for port corresponds to `current-output-port`, a parameter object defined by library `(lispkit port)`. Providing `#f` as port will send the output to `/dev/null`. input is an optional string which can be used to pipe data into the binary as input. The current implementation is not able to handle interactive binaries. `system-call` returns the result code for executing the binary (`0` refers to a regular exit).

    > (system-call "/bin/ls" '(-a -l))
    total 863816
    drwx------@  47 objecthub    1504 Jun  8 10:56 Desktop
    drwx------@  96 objecthub    3072 Jun  7 16:39 Documents
    drwx------@ 589 objecthub   18848 May 31 16:59 Downloads
    drwx------@  41 objecthub    1312 Dec 19 22:51 Google Drive
    drwx------@  84 objecthub    2688 Feb 15 18:32 Library
    drwx------+  16 objecthub     512 Oct 20  2019 Movies
    drwx------+  10 objecthub     320 Oct 20  2019 Music
    drwx------+  10 objecthub     320 May 17 18:37 Pictures
    drwxr-xr-x+   5 objecthub     160 Nov 23  2016 Public
    0
    > (system-call "/usr/bin/bc" '(-q) '() (current-output-port) "10*(11+9)/2\n")
    100
    0