1RCSINTRO(1L) RCSINTRO(1L)
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6 rcsintro - introduction to RCS commands
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9 The Revision Control System (RCS) manages multiple revisions of text
10 files. RCS automates the storing, retrieval, logging, identification,
11 and merging of revisions. RCS is useful for text that is revised fre‐
12 quently, for example programs, documentation, graphics, papers, form
13 letters, etc.
14 The basic user interface is extremely simple. The novice only needs to
16 learn two commands: ci(1L) and co(1L). Ci, short for "check in",
17 deposits the contents of a text file into an archival file called an
18 RCS file. An RCS file contains all revisions of a particular text file.
19 Co, short for "check out", retrieves revisions from an RCS file.
20 Functions of RCS
22 · Storage and retrieval of multiple revisions of text. RCS saves
24 all old revisions in a space efficient way. Changes no longer
25 destroy the original, because the previous revisions remain
26 accessible. Revisions can be retrieved according to ranges of
27 revision numbers, symbolic names, dates, authors, and states.
28 · Maintenance of a complete history of changes. RCS logs all
30 changes automatically. Besides the text of each revision, RCS
31 stores the author, the date and time of check-in, and a log mes‐
32 sage summarizing the change. The logging makes it easy to find
33 out what happened to a module, without having to compare source
34 listings or having to track down colleagues.
35 · Resolution of access conflicts. When two or more programmers
37 wish to modify the same revision, RCS alerts the programmers and
38 prevents one modification from corrupting the other.
39 · Maintenance of a tree of Revisions. RCS can maintain separate
41 lines of development for each module. It stores a tree structure
42 that represents the ancestral relationships among revisions.
43 · Merging of revisions and resolution of conflicts. Two separate
45 lines of development of a module can be coalesced by merging.
46 If the revisions to be merged affect the same sections of code,
47 RCS alerts the user about the overlapping changes.
48 · Release and configuration control. Revisions can be assigned
50 symbolic names and marked as released, stable, experimental,
51 etc. With these facilities, configurations of modules can be
52 described simply and directly.
53 · Automatic identification of each revision with name, revision
55 number, creation time, author, etc. The identification is like
56 a stamp that can be embedded at an appropriate place in the text
57 of a revision. The identification makes it simple to determine
58 which revisions of which modules make up a given configuration.
59 · Minimization of secondary storage. RCS needs little extra space
61 for the revisions (only the differences). If intermediate revi‐
62 sions are deleted, the corresponding deltas are compressed
63 accordingly.
64 Getting Started with RCS
67 Suppose you have a file f.c that you wish to put under control of RCS.
69 Invoke the check-in command
70 ci f.c
72 This command creates the RCS file f.c,v, stores f.c into it as revision
74 1.1, and deletes f.c. It also asks you for a description. The descrip‐
75 tion should be a synopsis of the contents of the file. All later check-
76 in commands will ask you for a log entry, which should summarize the
77 changes that you made.
78 Files ending in ,v are called RCS files (`v' stands for `versions'),
80 the others are called working files. To get back the working file f.c
81 in the previous example, use the check-out command
82 co f.c
84 This command extracts the latest revision from f.c,v and writes it into
86 f.c. You can now edit f.c and check it back in by invoking
87 ci f.c
89 Ci increments the revision number properly. If ci complains with the
91 message
92 ci error: no lock set by <your login>
94 then your system administrator has decided to create all RCS files with
96 the locking attribute set to `strict'. In this case, you should have
97 locked the revision during the previous check-out. Your last check-out
98 should have been
99 co -l f.c
101 Of course, it is too late now to do the check-out with locking, because
103 you probably modified f.c already, and a second check-out would over‐
104 write your modifications. Instead, invoke
105 rcs -l f.c
107 This command will lock the latest revision for you, unless somebody
109 else got ahead of you already. In this case, you'll have to negotiate
110 with that person.
111 Locking assures that you, and only you, can check in the next update,
113 and avoids nasty problems if several people work on the same file.
114 Even if a revision is locked, it can still be checked out for reading,
115 compiling, etc. All that locking prevents is a CHECK-IN by anybody but
116 the locker.
117 If your RCS file is private, i.e., if you are the only person who is
119 going to deposit revisions into it, strict locking is not needed and
120 you can turn it off. If strict locking is turned off, the owner of the
121 RCS file need not have a lock for check-in; all others still do. Turn‐
122 ing strict locking off and on is done with the commands
123 rcs -U f.c and rcs -L f.c
125 If you don't want to clutter your working directory with RCS files,
127 create a subdirectory called RCS in your working directory, and move
128 all your RCS files there. RCS commands will look first into that direc‐
129 tory to find needed files. All the commands discussed above will still
130 work, without any modification. (Actually, pairs of RCS and working
131 files can be specified in 3 ways: (a) both are given, (b) only the
132 working file is given, (c) only the RCS file is given. Both RCS and
133 working files may have arbitrary path prefixes; RCS commands pair them
134 up intelligently).
135 To avoid the deletion of the working file during check-in (in case you
137 want to continue editing), invoke
138 ci -l f.c or ci -u f.c
140 These commands check in f.c as usual, but perform an implicit check-
142 out. The first form also locks the checked in revision, the second one
143 doesn't. Thus, these options save you one check-out operation. The
144 first form is useful if locking is strict, the second one if not
145 strict. Both update the identification markers in your working file
146 (see below).
147 You can give ci the number you want assigned to a checked in revision.
149 Assume all your revisions were numbered 1.1, 1.2, 1.3, etc., and you
150 would like to start release 2. The command
151 ci -r2 f.c or ci -r2.1 f.c
153 assigns the number 2.1 to the new revision. From then on, ci will num‐
155 ber the subsequent revisions with 2.2, 2.3, etc. The corresponding co
156 commands
157 co -r2 f.c and co -r2.1 f.c
159 retrieve the latest revision numbered 2.x and the revision 2.1, respec‐
161 tively. Co without a revision number selects the latest revision on the
162 "trunk", i.e., the highest revision with a number consisting of 2
163 fields. Numbers with more than 2 fields are needed for branches. For
164 example, to start a branch at revision 1.3, invoke
165 ci -r1.3.1 f.c
167 This command starts a branch numbered 1 at revision 1.3, and assigns
169 the number 1.3.1.1 to the new revision. For more information about
170 branches, see rcsfile(5L).
171 Automatic Identification
174 RCS can put special strings for identification into your source and
176 object code. To obtain such identification, place the marker
177 $Header$
179 into your text, for instance inside a comment. RCS will replace this
181 marker with a string of the form
182 $Header: filename revision_number date time author state
184 $
185 With such a marker on the first page of each module, you can always see
187 with which revision you are working. RCS keeps the markers up to date
188 automatically. To propagate the markers into your object code, simply
189 put them into literal character strings. In C, this is done as follows:
190 static char rcsid[] = "$Header$";
192 The command ident extracts such markers from any file, even object code
194 and dumps. Thus, ident lets you find out which revisions of which mod‐
195 ules were used in a given program.
196 You may also find it useful to put the marker $Log$ into your text,
198 inside a comment. This marker accumulates the log messages that are
199 requested during check-in. Thus, you can maintain the complete history
200 of your file directly inside it. There are several additional identi‐
201 fication markers; see co(1L) for details.
202
204 Author: Walter F. Tichy, Purdue University, West Lafayette, IN, 47907.
205 Revision Number: 1.2 ; Release Date: 87/02/27 .
206 Copyright © 1982 by Walter F. Tichy.
207
209 ci(1L), co(1L), ident(1L), merge(1L), rcs(1L), rcsdiff(1L),
210 rcsmerge(1L), rlog(1L)
211 Walter F. Tichy, "Design, Implementation, and Evaluation of a Revision
212 Control System," in Proceedings of the 6th International Conference on
213 Software Engineering, IEEE, Tokyo, Sept. 1982.
214Purdue University May 11, 1983 RCSINTRO(1L)