Modes

V provides multiple modes of running while the default (v or v runrepl) throws you into the REPL (Read-Execute-Print-Loop) console where you can try the language or write small scripts.

REPL

Although not in the way as it is for Python or JavaScript, this interpreter-like mode takes your code and in the background writes it to a temporary .v file which is then compiled and run. V then returns the output back to you in the console.

v  # or v runrepl
root@16b5a9d05074:/opt/vlang# v
V 0.1.21 b51b885
Use Ctrl-C or `exit` to exit
>>>

The console provides a simple help command that lists all available console commands:

>>> help

V 0.1.21 b51b885
  help                   Displays this information.
  Ctrl-C, Ctrl-D, exit   Exits the REPL.
  clear                  Clears the screen.

Note

Currently there is a hidden step between compiling .v file and running the final program. V requires a C compiler present on the system and attempts to compile .v file to .c which is then compiled to machine code a CPU understands. After that V runs the binary produced by the C compiler and retrieves output back.

Warning

Currently there is no support for command history, therefore arrows, Control-P, Alt-P or any combination of them will result in an escape code printed to the console.

>>> ^[[A
>>> ^P
>>> ^[p
>>> ^[^P
>>> ^[[1;5A
>>> ^[[1;3A

By default you have an access to the builtin module

>>> println("Hello, world!")
Hello, world!

// or even

>>> print("Hello, world!")
Hello, world!

In its simplest form it can be used as a calculator:

>>> print(1 + 1)
2

For more examples check Calculator test cases.

Compiler

V executable when provided with an argument that contains a .v suffix will open that file, compile it and produce a same-named binary.

// helloworld.v
println("Hello, world!")  // with a new like character \n
print("Hello, world!")    // without a new like character

Compile with:

v helloworld.v
./helloworld

Note

In case you can’t execute the output file try changing the file into an executable with chmod +x <file>.

Runner

Similar to REPL mode, this mode in the background compiles and attempts to run your file.

v run helloworld.v