my tech blog

To iterate is human, to recurse divine

Erlang Shell Cheat Sheet

The erlang shell, erl, is a great tool while developing erlang code. Since I’m writing code in erlang sporadically I thought that writing a cheat sheet for the erl shell might help me to remember the basic commands better.

The man pages for the erlang shell can be found here, man shell and man c. The implementation of the modules can be found here on github, shell module and c module.

getting help

  • help() - will display all of the available commands in the shell, which makes the list below pointless :-)

quit the shell

  • q() - will call init:stop() internally, however be careful when using this since you will be shutting down the erlang runtime, not a good idea if you have connected to a remote shell.
  • Ctrl-G and then q - use this when connected to a remote shell.

command history

  • h() - displays the latest 20 (default value) commands used in the shell.
  • history(N) - sets the history length of the command above.
  • results(N) - sets the history length of the results for previous commands.
  • e(N) - executes command N again (the prompt in the shell is showing the current N for each command). Can be negative, e.g. e(-1), will execute previous command.
  • v(N) - get the value from command N and use it in the current command. Can be negative, e.g. v(-1), will use the value from the previous command.
  • - will navigate backward in the history list.
  • - will navigate forward in the history list.

variables

  • b() - displays all the current variable bindings in the shell.
  • f() - drops all the current variable bindings in the shell.
  • f(Variable) - drops the specified variable binding in the shell.

navigate the filesystem

  • pwd() - print working directory, the pwd() will start in the same directory as the shell were started.
  • ls() - list directory contents.
  • cd(Path) - change working directory, Path is a string, e.g. cd(“..”) or cd(“src”).

working with source code and modules

  • c(File) - compiles the given file and loads the code in the shell. It will also make some extra work if you recompile the code so that no old code is running.
  • lc(Files) - compiles the given files the same way as the command above.
  • m() - displays all loaded modules in the shell.
  • m(Module) - displays information about the given module.

editing expressions

The erlang shell is using the same key bindings as emacs when you are working/editing text in the shell.

  • C-a - move the cursor to the beginning of the line.
  • C-e - move the cursor to the end of the line.
  • C-b - move the cursor left one character.
  • C-f - move the cursor right one character.

what else

This is just some basic stuff that is good to know about the erlang shell. There is a lot more stuff to know and learn about the shell like connect to remote shells, user switch command (Ctrl-G), working with records and more. However more about these things can be found in the links to the man pages at the beginning of this post.

Comments