Introduction

lcli (pronounced "Elk-ly") is a semi-opinionated library for creating command line tools and supporting options (flags) and arguments (non-flag parameters) parsing. Regular options parsing is done using the Erlang getopt community library. lcli manages the handling of commands and nested subcommands.

This library attempts to provide CLI-tool-building capabilities to LFE developers in such a way that it feels LFE-idiomatic. Two excellet libraries have served as inspiration, from two different programming languages: Rust's clap and Go's kong (with the former having a bigger influence).

Erlang `getopt` Wrapper and More

lcli provides a very thing wrapper around getopt, basically converting to and from the getopt spec tuple with LFE/Erlang maps.

In addition, lcli provides command and subcommand support where the command spec is a superset of the getopt spec (thus allowing us to use the getopt library transparently).

With lcli, you have the option of defining specs as maps or as getopt specs; each has its own aestheic tradeoffs. Note that with maps, the name is optional (taken from the long option name if missing).

Example map specs:

'(#m(long "host" short #\h type string default "localhost"
     help "Database server host")
  #m(long "port" short #\p type integer
     help "Database server port")
  #m(long "dbname" type string default "users"
     help "Database name")
  #m(name xml short #\x help "Output data in XML")
  #m(long "verbose" short #\v type integer help "Verbosity level")
  #m(name file type string help "Output file"))

Example getopt specs:

'(#(host #\h "host" #(string "localhost") "Database server host")
  #(port #\p "port" integer "Database server port")
  #(dbname undefined "dbname"#(string "users") "Database name")
  #(xml #\x "xml" undefined undefined "Output data in XML")
  #(verbose #\v "verbose" integer "Verbosity level")
  #(file undefined undefined string "Output file"))

Differences from `lfescript` ↟

This library does not use lfescript as its basis, but rather the lfe executable itself. As such, a main function is not run automatically. Instead, the final line of the script must call the entrypoint function.