Basic concepts

• RCS repository: either foo,v or RCS/foo,v
• Checking files in and out
• Locks

Basic commands

ci

checks in and removes existing copy

ci -u

checks in and releases lock (file becomes read-only)

ci -l

checks in and retains lock (file is rw)

co

checks out with no lock (read-only)

co -u

checks out with no lock (read-only)

co -l

checks out and obtains exclusive lock

rlog

look at log

rcsdiff

compare revisions and create patches. Example:

	rcsdiff -r1.4 -u foo.c
	

rcs -u

break locks

rcs

do random things to rcs file

Lots of other options

• History trees
• Merging versions
• Symbolic version names
• For info, read man pages:
  • rcsintro, rcsdiff, ci, co, rcs, rcsmerge

Logs and headers in files

• Put strings into files and RCS will expand them:

  	$Header$
  	$Id$
  	$Date$
  	$Log$
  	$Author$
  	

• For example, $Header$ gets expanded to something like this:

  	$Header: /afs/sipb.mit.edu/project/iap/unixsoftdev/examples/rcs/RCS/foo,v 1.3 95/01/19 19:24:27 nygren Exp $
  	

Reverting to old versions without dealing with branch messiness

• Reverting to an old version by checking out the old version and then checking it back in would normally force you to deal with branches which can get messy.
• An easier way is to do something like:

    ci -l foo     # save old version before clobbering
                  # plus get a lock on the file
    co -r1.5 foo  # revert to version 1.5
    ci -u foo     # check in the reverted file and unlock
  	

Diffs and patches

• Creating diff's:

      diff file1 file2
  
  	 or
  
      rcsdiff -r1.5 -c foo  # changes from 1.5 to present
  	

• Types of diffs
  • Old style: diff
  • Context: diff -c
  • Unified (my favorite): diff -u
  • Ed (I've never seen them used): diff -e
• Examples
• Applying diffs/patches:

  	patch < foo.patch -p -E
  	

  • Modifies the file with the old filename
  • Patch can have more than one diff in it
  • Pre-patch file is renamed to file.orig
  • Rejected parts of patch are renamed to file.rej in the proper directory

Alternatives

• SCCS - like RCS but not as available at MIT
• CVS - layer on top of RCS which allows for dealing with really big source trees