apenwarr-redo/docs/redo-ifcreate.md
Avery Pennarun f6fe00db5c Directory reorg: move code into redo/, generate binaries in bin/.
It's time to start preparing for a version of redo that doesn't work
unless we build it first (because it will rely on C modules, and
eventually be rewritten in C altogether).

To get rolling, remove the old-style symlinks to the main programs, and
rename those programs from redo-*.py to redo/cmd_*.py.  We'll also move
all library functions into the redo/ dir, which is a more python-style
naming convention.

Previously, install.do was generating wrappers for installing in
/usr/bin, which extend sys.path and then import+run the right file.
This made "installed" redo work quite differently from running redo
inside its source tree.  Instead, let's always generate the wrappers in
bin/, and not make anything executable except those wrappers.

Since we're generating wrappers anyway, let's actually auto-detect the
right version of python for the running system; distros can't seem to
agree on what to call their python2 binaries (sigh). We'll fill in the
right #! shebang lines.  Since we're doing that, we can stop using
/usr/bin/env, which will a) make things slightly faster, and b) let us
use "python -S", which tells python not to load a bunch of extra crap
we're not using, thus improving startup times.

Annoyingly, we now have to build redo using minimal/do, then run the
tests using bin/redo.  To make this less annoying, we add a toplevel
./do script that knows the right steps, and a Makefile (whee!) for
people who are used to typing 'make' and 'make test' and 'make clean'.
2018-12-04 02:53:40 -05:00

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# NAME
redo-ifcreate - rebuild the current target if source files are created
# SYNOPSIS
redo-ifcreate [sources...]
# DESCRIPTION
Normally redo-ifcreate is run from a .do file that has been
executed by `redo`(1). See `redo`(1) for more details.
redo-ifcreate takes a list of nonexistent files (*sources*)
and adds them as dependencies to the current target (the
one calling redo-ifcreate). If any of those files are
created in the future, the target will be marked as needing
to be rebuilt.
If one of the given files exists at the time redo-ifcreate
is called, it will return a nonzero exit code.
If you want to declare dependencies on files that already
exist, use `redo-ifchange`(1) instead.
# REDO
Part of the `redo`(1) suite.
# CREDITS
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.
# SEE ALSO
`redo`(1), `redo-ifchange`(1), `redo-always`(1), `redo-stamp`(1)