I have implemented the build system redo as designed by DJB in Bourne Shell. To understand how redo can be simpler, more flexible, more powerful and more reliable than make, read Introduction to redo and/or redo: a top-down software build system.

The implementation itself depends only on GNU Core Utilities or BusyBox. It takes around twice the time of apenwarr's Python redo implementation to return from a dependency check while using fewer resources.

redo
the main program
redo-always
marks the current target as always needing to be rebuilt
redo-dot
prints redo dependency graph in DOT format (example output, example rendering)
redo-ifchange
adds dependencies for the current target (if a dependency changes, the target will be rebuilt)
redo-ifcreate
adds non-existence dependencies for the current target (if a non-existence dependency is created, the target will be rebuilt)
redo-ood
prints a list of all target files that are out of date
redo-targets
prints a list of all target files that exist (a target is a file redo can build)
redo-sources
prints a list of all source files that exist (a source is a dependency that is not a target)
redo-stamp
detects if the current target has changed (see apenwarr's documentation)

Frequently Asked Questions

How do I build a file with redo?

To build a file target, you have to create a dofile target.do with shell commands that write the intended result of the build either to standard output or to its parameter $3. Then run redo target.

The default target is all: redo without arguments executes commands from all.do.

What do the redo parameters $1, $2, $3 mean?

When redo runs a dofile, it gives it three parameters:

$1filename of target
$2basename of target, without extension if default dofile is used
$3filename of temporary output file that is renamed on build success

How does the extension removal in parameter $2 work?

Redo removes the extension that it gets from the default dofile filename:

TargetDofileParameter $2
a.b.ca.b.c.doa.b.c
a.b.cdefault.doa.b.c
a.b.cdefault.c.doa.b
a.b.cdefault.b.c.doa

How do I declare dependencies with redo?

Use the redo-ifchange command in a dofile: redo-ifchange dependency inside target.do means: If the target is built, the dependency is built if it does not exist and recorded as a dependency. On subsequent builds, if dependency does not exist or has changed since the last build, both dependency and target are rebuilt.

How does this redo implementation check dependencies?

For dependency checking, this implementation of redo checks the dependencies' ctime against the stored ctime. If the ctime differs, it checks the dependencies' md5sum against the stored md5sum. This is arguably more useful than just using ctime.

How do I declare non-existence dependencies with redo?

Use the redo-ifcreate command in a dofile: redo-ifcreate ne_dependency inside target.do means: If target is built, the non-existing file ne_dependency is recorded as a non-existence dependency. If ne_dependency exists on subsequent builds, target is rebuilt.

What are command line options for this redo implementation?

Short optionLong optionEffect
-d--debugprint dependency checks as they happen
-h--helpprint usage instructions and exit
-s--shufflerandomize build order to find dependency bugs
-x--xtraceprint commands as they are executed (variables expanded)

How can I use this redo implementation to build in parallel?

You can use the shell builtins & and wait to execute commands asynchronously. The following line in a dofile builds targets a and b in parallel: redo-ifchange a & redo-ifchange b & ; wait