redo - rebuild target files when source files have changed
redo [options...] [targets...]
redo is a simple yet powerful tool for rebuilding target
files, and any of their dependencies, based on a set of
rules. The rules are encoded in simple
called '.do scripts.'
redo supports GNU
make(1)-style parallel builds using the
-j option; in fact, redo's parallel jobserver is compatible
with GNU Make, so redo and make can share build tokens with
each other. redo can call a sub-make (eg. to build a
subproject that uses Makefiles) or vice versa (eg. if a
make-based project needs to build a redo-based subproject).
Unlike make, redo does not have any special syntax of its own; each target is built by running a .do file, which is simply a shell script that redo executes for you with a particular environment and command-line arguments.
If no targets are specified, redo pretends you specified
exactly one target named
Note that redo always rebuilds the given targets
(although it may skip rebuilding the targets' dependencies
if they are up to date). If you only want to rebuild
targets that are not up to date, use
A .do script can call redo recursively to build its dependencies.
To avoid confusion caused by multiple programs trying to
use the terminal, inside .do scripts, stdin is normally
redirected to /dev/null. The only exception is if the
option is not given and
--no-log is used.
-j, --jobs=maxjobs : execute at most maxjobs .do scripts in parallel. The default value is 1.
: print dependency checks as they happen. You can use
this to figure out why a particular target is/isn't being
rebuilt when your .do script calls it using
: pass the -v option to /bin/sh when executing scripts.
This normally causes the shell to echo the .do script lines
to stderr as it reads them. Most shells will print the
exact source line (eg.
echo $3) and not the
substituted value of variables (eg.
: pass the -x option to /bin/sh when executing scripts.
This normally causes the shell to echo exactly which
commands are being executed. Most shells will print
the substituted variables (eg.
mytarget.redo.tmp) and not the original source line
-k, --keep-going : keep building as many targets as possible even if some of them return an error. If one target fails, any target that depends on it also cannot be built, of course.
: randomize the order in which requested targets are
built. Normally, if you run
redo a b c, the targets
will be built exactly in that order: first
c. But if you use
-j, they might end up
being built in parallel, so it isn't safe to rely on
this precise ordering. Using
--shuffle, redo will
build its targets in random order even without
which makes it easier to find accidental dependency
problems of this sort. NOTE: if you really just want
to guarantee that
a is built, then
can just run three
redo commands consecutively.
Because your .do script is just a script, it will not
be accidentally parallelized.
--no-details : display only the messages from redo itself, not the other messages produced by build scripts. Generally this gives you a list of which targets were built, but not detailed logs, warnings, or errors.
--no-status : don't display the running build status at the bottom of the screen. (Unless this option is specified, the status line will be enabled if using --follow, if stderr is a terminal.) If stderr is not a terminal, you can force enable the status line using --status.
--no-pretty : display "raw" redo log lines (@@REDO events) rather than using a human-readable format. The default is --pretty.
--no-color : when using --pretty and writing to a terminal, colorize the output to make results stand out more clearly. If not writing to a terminal, you can use --color to force colorized output.
--no-log : don't capture stderr log messages from build scripts. This prevents redo-log from redisplaying the logs later, and if using --jobs, causes output from all parallel jobs to be jumbled together. This was the only behaviour available before redo-0.30. The default is --log.
--debug-locks : print messages about acquiring, releasing, and waiting on locks. Because redo can be highly parallelized, one instance may end up waiting for a target to be built by some other instance before it can continue. If you suspect this is causing troubles, use this option to see which instance is waiting and when.
--debug-pids : add the process id of the particular redo instance to each output message. This makes it easier to figure out which sub-instance of redo is doing what.
--version : displays the redo version number.
The core of redo is extremely simple. When you type
targetname, then it will search for a matching .do file
based on a simple algorithm. For example, given a target
mytarget.a.b.c.d, redo will look for a .do file in
the following order:
In all cases, the .do file must be in the same directory as
the target file, or in one of the target's parent
directories. For example, if given a target named
../a/b/xtarget.y, redo will look for a .do file in the
The first matching .do file is executed as a
script. The .do script is always executed with the current
working directory set to the directory containing the .do
file. Because of that rule, the
following two commands always have exactly identical
redo path/to/target cd path/to && redo target
make(1), these commands have confusingly
different semantics. The first command would look for a
./Makefile, while the
second command would look for a target named
./path/to/Makefile. The two Makefiles might give
completely different results, and it's likely that the
first command would have incomplete dependency information.
redo does not have this problem.)
The three arguments passed to the .do script are:
- $1: the target name (eg. mytarget.a.b)
- $2: the basename of the target, minus its extension (eg. mytarget)
- $3: a temporary filename that the .do script should write its output to.
Instead of using $3, the .do script may also write the produced data to stdout.
If the .do file is in the same directory as the target, $1 is guaranteed to be a simple filename (with no path component). If the .do file is in a parent directory of the target, $1 and $3 will be relative paths (ie. will contain slashes).
redo is designed to update its targets atomically, and only if the do script succeeds (ie. returns a zero exit code). Thus, you should never write directly to the target file, only to $3 or stdout.
Normally, a .do script will call other .do scripts
recursively, by running either
redo (which will always
build the sub-target) or
redo-ifchange (which only
rebuilds the sub-target if its dependencies have changed).
redo-ifchange is also the way your .do script
declares dependencies on other targets; any target that is
redo-ifchanged during your .do script's execution is both
executed (if needed) and added as a dependency.
You may have heard that 'recursive make is considered
make(1), redo does correct locking, state
management, and global dependency checking, so none of the
arguments in that essay apply to redo. In fact, recursive
redo is really the only kind of redo.
When writing a .do script, it will probably need to run one or more of the following commands:
: to build a sub-target unconditionally.
: to declare dependencies on the given files, and build them if
they don't yet exist or are outdated.
: to tell redo that the current target must be rebuilt if
the given source files (which must not yet exist) get created.
: to tell redo that the current target must always be
rebuilt, even if none of its dependencies have changed.
(You might need this for targets that depend on more than just
file contents. For example, the output of
changes when files are created or deleted, but there is no way
for redo to know that without re-running the command.)
echo "stamp contents..." | redo-stamp
: to tell redo that even though the current target has
been rebuilt, it may not actually be any different from
the previous version, so targets that depend on it
might not need to be rebuilt. Often used in
redo-always to reduce the impact of
always rebuilding a target.
There are also some less common ones:
: Get a list of all known targets that have been built before, but
are currently out of date.
: Get a list of all known targets that have been built before.
: Get a list of all known redo source files that still exist.
: Explain the search path used to find a .do file for the given
The original concept for
redo was created by D. J.
Bernstein and documented on his web site
(http://cr.yp.to/redo.html). This independent implementation
was created by Avery Pennarun and you can find its source
code at http://github.com/apenwarr/redo.