-% NIT(1)
-
# NAME
-Interprets and debugs Nit programs.
+nit - interprets and debugs Nit programs.
+
+# SYNOPSIS
+
+nit [*options*] FILE [ARG]...
+
+nit [*options*] - [ARG]...
+
+nit [*options*] -e COMMAND [ARG]...
+
+# DESCRIPTION
+
+`nit` is the current official interpreter.
+It takes the main module of a program as the first argument then the options and commands of the program.
+
+ $ nit examples/hello_world.nit
+ hello world
+
+If `-` is used instead of a module, then the program is read from the standard input.
+The whole program is read before its interpretation starts.
+
+The Nit interpreter is usable and valid as a *shebang* interpreted directive.
+It is however recommended to use with `/usr/bin/env` because the location of the executable is not standardized.
+
+ #!/usr/bin/env nit
+ print "hello world"
+
+The interpreter includes an interactive debugger, it supports basic commands used for debugging a program much like GDB or such.
+See the `DEBUGGER` section for details.
-# SYNOPSYS
-nit [*options*]...
+The behavior of the interpreter may differs slightly from the compiler.
+
+First, the interpreted is the reference implementation for the specification of the Nit language.
+That means if `nitc` and `nit` have a different behavior on a same program, it is likely that `nit` is right and `nitc` is wrong.
+
+Second, the FFI is not yet implemented in the interpreter.
+Only a subset of the standard methods are implemented with some hard-coded behaviors.
+While it is enough to use most of the standard library, a lot of additional libraries may not be usable by the interpreter.
+
+Last, `nit` is the *Naive Interpretation Tool*, it means that it is slow and may take an average of 50.000% in overhead comparatively to `nitc`(it also means that `nitc` is fast).
+In practice, the slowness is not an issue for simple Nit scripts;
+it is not a big deal if `nit` takes millisecond to execute programs even if `nitc` only need microseconds.
+
# OPTIONS
-`-W`, `--warn`
-: Show more warnings
+Most options are the same than `nitc(1)`.
+Here, only the specific one are indicated.
+
+Note that, unlike in other Nit tools, the options *MUST* be indicated before the main module of a program.
+Whatever follows it is used as arguments of the interpreted program.
+
+ $ nit -e 'print args.first' -v
+ -v
+
+## COMMAND
+
+### `-e`
+Specifies the program from command-line.
+
+The `-e` option runs a program written on the command line.
+Like with ruby, perl, bash and other script language.
+
+ $ nit -e 'print 5+5'
+ 10
+
+### `-n`
+Repeatedly run the program for each line in file-name arguments.
+
+If no arguments are given, then `nit` iterates over the lines of the standard input (stdin).
+
+ $ echo "hello world" | nit -n -e 'print sys.line.capitalized'
+ Hello World
+
+If some arguments are given, then `nit` considers that each argument is a filepath then it iterates on their lines.
+
+## INTERPRETATION OPTIONS
+
+### `--discover-call-trace`
+Trace calls of the first invocation of methods.
+
+Each time a method is invoked for the first time, its information is printed on the standard output for error (`stderr`).
+
+This option helps the user to have a simplified but humanly readable overview of the behavior of a particular program execution.
+
+## DEBUGGER OPTIONS
+
+### `-d`
+Launches the target program with the debugger attached to it.
+
+### `-c`
+Launches the target program with the interpreter, such as when the program fails, the debugging prompt is summoned.
+
+### `--socket`
+Launches the target program with raw output on the network via sockets.
+
+### `--websocket`
+Launches the target program with output on the network via websockets.
+
+### `--port`
+Sets the debug port (Defaults to 22125) - Must be contained between 0 and 65535.
+
+## OTHER OPTIONS
+
+### `--vm`
+Run the virtual machine instead of the naive interpreter (experimental).
+
+The virtual machine is currently under heavy development and, unless you are developing the vm, there is no reason to use this option yet.
+
+### `-o`
+Does nothing. Used for compatibility.
+
+
+# DEBUGGER
+
+To use use the debugger, launch your program using the nit interpreter `nit` with `-d` option.
+
+It is also possible to execute the program normally until an error is encountered using the `-c` option.
+
+A remote debugger is also available, it can be used with the client-side executable `nitdbg_client`.
+
+On the client side, the debugger works like the previous one, input some commands when debugging a program, except you have to launch the server before trying to debug.
+
+## DEBUGGER FEATURES
-`-w`, `--warning`
-: Show/hide a specific warning
+When using a debugger, a must-have is the possibility to control execution of your program by stepping over, in and out of a line/snippet of code. The nit debugger allows you to do that.
-`-q`, `--quiet`
-: Do not show warnings
+You can add/remove breakpoints on instructions, so that the execution will stop when the execution reaches the specified line of the specified file.
-`--stop-on-first-error`
-: Stop on first error
+When an error is encountered, the debugger gives you the chance of inputting commands before exiting.
-`--no-color`
-: Do not use color to display errors and warnings
+The debugger also gives the possibility of printing the values of the requested variables.
-`--log`
-: Generate various log files
+The modification of variables at runtime is possible too, but only if the variables are of primitive types (until it becomes possible).
-`--log-dir`
-: Directory where to generate log files
+Also, you probably won't want to type a long variable name every time you wish to print its value, the debugger has the possibility of setting aliases to replace the awfully long and cryptic name of that variable you try to access by a beautiful alias.
-`-h`, `-?`, `--help`
-: Show Help (This screen)
+If you want to trace the modifications or uses of a variable of your choice, the trace command will be perfect for you as it will print or break when encountering the variable of your choice.
-`--version`
-: Show version and exit
+## DEBUGGER COMMANDS
-`--set-dummy-tool`
-: Set toolname and version to DUMMY. Useful for testing
+### `n`
+Proceeds to the next instruction (step-over)
-`-v`, `--verbose`
-: Verbose
+### `s`
+Steps in an instruction
-`--bash-completion`
-: Generate bash_completion file for this program
+### `finish`
+Steps out of an instruction
-`--stub-man`
-: Generate a stub manpage in pandoc markdown format
+### `c`
+Continues the execution until a breakpoint is encountered or until an error/end of program
-`--disable-phase`
-: DEBUG: Disable a specific phase; use `list` to get the list.
+### `b/break line_number`
+Adds a breakpoint on line *line_number* for the current file
-`-I`, `--path`
-: Set include path for loaders (may be used more than once)
+### `b/break file line_number`
+Adds a breakpoint on line *line_number* for the file *file* (Don't forget to add the .nit extension to the command)
-`--only-parse`
-: Only proceed to parse step of loaders
+### `d/delete line_number`
+Removes a breakpoint on line *line_number* for the current file
-`--only-metamodel`
-: Stop after meta-model processing
+### `d/delete file line_number`
+Removes a breakpoint on line *line_number* for the file *file*
-`--ignore-visibility`
-: Do not check, and produce errors, on visibility issues.
+### `kill`
+Kills the current program (produces a stack trace)
-`--discover-call-trace`
-: Trace calls of the first invocation of a method
+### `variable = value`
+Sets the value of *variable* to *value* (Only supports primitive types for now : Bool, Char, Int, Float)
-`-d`
-: Launches the target program with the debugger attached to it
+### `p/print variable_name`
+Prints the value of the variable *variable_name*
-`-c`
-: Launches the target program with the interpreter, such as when the program fails, the debugging prompt is summoned
+### `p/print stack`
+Prints a stack trace starting with the current frame
-`--socket`
-: Launches the target program with raw output on the network via sockets
+### `p/print variable_name[index]`
+Prints the value of the variable contained at the index *index* of variable *variable_name* (*variable_name* must be a subtype of SequenceRead)
-`--websocket`
-: Launches the target program with output on the network via websockets
+### `p/print variable_name[index_from..index_to]`
+Prints the values of all the variables contained from index *index_from* up to *index_to* in the variable *variable_name*
-`--port`
-: Sets the debug port (Defaults to 22125) - Must be contained between 0 and 65535
+All the print commands also work on any dimension SequenceRead collection.
-`-o`
-: compatibility (does noting)
+### `variable_name as alias`
+Sets an alias *alias* for the variable *variable_name*
-`-m`
-: Additionals module to min-in
+### `trace variable_name [break/print]`
+Traces the uses of the variable you chose to trace by printing the statement it appears in or by breaking on each use. (The [break/print] part is not mandatory, by default, the print option will be used)
-`-e`
-: Specifies the program from command-line
+### `untrace variable_name`
+Removes the trace on the variable you chose to trace earlier in the program
-`-n`
-: Repeatedly run the program for each line in file-name arguments
# SEE ALSO
nitlanguage / nit.git / blobdiff