Introduction to Revise

Revise.jl may help you keep your Julia sessions running longer, reducing the need to restart when you make changes to code. With Revise, you can be in the middle of a session and then update packages, switch git branches or stash/unstash code, and/or edit the source code; typically, the changes will be incorporated into the very next command you issue from the REPL. This can save you the overhead of restarting, loading packages, and waiting for code to JIT-compile.

Installation

You can obtain Revise using Julia's Pkg REPL-mode (hitting ] as the first character of the command prompt):

(v0.7) pkg> add Revise

or with using Pkg; Pkg.add("Revise").

Usage example

(v0.7) pkg> dev Example
[...output related to installation...]

julia> using Revise        # importantly, this must come before `using Example`

julia> using Example

julia> hello("world")
"Hello, world"

julia> Example.f()
ERROR: UndefVarError: f not defined

julia> edit(hello)   # opens Example.jl in the editor you have configured

# Now, add a function `f() = π` and save the file

julia> Example.f()
π = 3.1415926535897...

Revise is not tied to any particular editor. (The EDITOR or JULIA_EDITOR environment variables can be used to specify your preference.)

It's even possible to use Revise on code in Julia's Base module or its standard libraries: just say Revise.track(Base) or using Pkg; Revise.track(Pkg). For Base, any changes that you've made since you last built Julia will be automatically incorporated; for the stdlibs, any changes since the last git commit will be incorporated.

See Using Revise by default if you want Revise to be available every time you start julia.

What Revise can track

Revise is fairly ambitious: if all is working you should be able to track changes to

any package that you load with import or using
any script you load with includet
any file defining Base julia itself (with Revise.track(Base))
any file defining Core.Compiler (with Revise.track(Core.Compiler))
any of Julia's standard libraries (with, e.g., using Unicode; Revise.track(Unicode))

The last two require that you clone Julia and build it yourself from source.

If Revise doesn't work as expected

If Revise isn't working for you, here are some steps to try:

See Configuration for information on customization options. In particular, some file systems (like NFS) might require special options.
Revise can't handle all kinds of code changes; for more information, see the section on Limitations.
Try running test Revise from the Pkg REPL-mode. If tests pass, check the documentation to make sure you understand how Revise should work. If they fail (especially if it mirrors functionality that you need and isn't working), see Fixing a broken or partially-working installation for some suggestions.

If you still encounter problems, please file an issue.