An Introduction to the Source Code Control System
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1. type the value of this fag replaces the Y keyword fix Remove a delta and reedit it delget Do a delta followed by a get deledit Do a delta followed by an edit 2 Id Keywords Z Expands to for the what command to fi nd M The current module name e g prog c 1 The highest SID applied W A shorthand for Z M lt tab gt 1 G The date of the delta corresponding to the 1 keyword PR The current release number i e the fi rst component of the 1 keyword Y Replaced by the value of the t fhg set by admin2. 14 Further Information The SCCS PWB User s Manual gives a deeper description of how to use SCCS Of particular interest are the numbering of branches the 1 fi le which gives a description of what deltas were used on a get and certain other SCCS commands The SCCS manual pages are a good last resort These should be read by software managers and by people who want to know everything about everything Both of these documents were written without the sccs front end in mind so most of the examples are slightly different from those in this document SCCS Introduction 14 Quick Reference 1 Commands The following commands should all be preceded with 8ccs This list is not exhaustive for more options see Further Information get edit delta unedit prt info check tell clean what admin Gets files for compilation not for editing Id keywords are expanded rSID Version to get p Send to standard output rather than to the actual fi le k Don t expand id keywords ilist List of deltas to include xlist List of deltas to exclude m Precede each line with SID of creating delta cdate Don t apply any deltas created after date Gets files for editing Id keywords are not expanded Should be matched with a delta com mand rSID Same as get If SID specifies a release that does not yet exist the highest numbered delta is retrieved and the new delta is numbered with SID b Create a b
3. text use prt t The admin command can be used safely any number of times on files A file need not be gotten for admin to work 12 Maintaining Different Versions Branches Sometimes it is convenient to maintain an experimental version of a program for an extended period while normal maintenance continues on the version in production This can be done using a branch Normally deltas continue in a straight line each depending on the delta before Creating a branch forks off a version of the program The ability to create branches must be enabled in advance using sccs admin fb prog c The fb fhg can be specifi ed when the SCCS fi le is fi rst created 12 1 Creating a branch To create a branch use sccs edit b prog c This will create a branch with for example SID 1 5 1 1 The deltas for this version will be numbered 1 5 1 n 12 2 Getting from a branch Deltas in a branch are normally not included when you do a get To get these versions you will have to say secs get r1 5 1 prog c 12 3 Merging a branch back into the main trunk At some point you will have fi nished the experiment and if it was successful you will want to incor porate it into the release version But in the meantime someone may have created a delta 1 6 that you don t want to lose The commands secs edit 11 5 1 1 1 5 1 prog c sccs delta prog c will merge all of your changes into the release system If some of the
4. But notice if you were to get them expanded accidently then your file would appear to be the same version forever more which would of course defeat the purpose Also if you should install a version of the program without expanding the id keywords it will be impossible to tell what version it is since all it will have is W or what ever 3 Creating SCCS Files To put source fi les into SCCS format run the following shell script from csh mkdir SCCS save foreach i ch sccs admin i i i mv i save i end This will put the named fi les into s fi les in the subdirectory SCCS The fi les will be removed from the cur rent directory and hidden away in the directory Save so the next thing you will probably want to do is to get all the fi les described below When you are convinced that SCCS has correctly created the s fi les you should remove the directory Save If you want to have id keywords in the files it is best to put them in before you create the s files If you do not admin will print No Id Keywords cm7 which is a warning message only This matches normal usage where the previous changes are not saved at all so all changes are automatically based on all other changes that have happened through history SCCS Introduction 3 4 Getting Files for Compilation To get a copy of the latest version of a file run sccs get prog c SCCS will respond 1 1 87 lines meaning that ver
5. any changes made to a file retrieved in this way will probably be lost 2 Geta file for editing This operation also retrieves a version of the file from the s file but this file is intended to be edited and then incorporated back into the s file Only one person may be editing a file at one time 3 Merge a file back into the s file This is the companion operation to 2 A new version number is assigned and comments are saved explaining why this change was made 2 Learning the Lingo There are a number of terms that are worth learning before we go any farther 2 1 S file The s file is a single file that holds all the different versions of your file The s file is stored in differ ential format i e only the differences between versions are stored rather than the entire text of the new version This saves disk space and allows selective changes to be removed later Also included in the s file This is version 1 21 of this document It was last modified on 12 5 80 SCCS Introduction 1 SCCS Introduction 2 is some header information for each version including the comments given by the person who created the version explaining why the changes were made 2 2 Deltas Each set of changes to the s fi le which is approximately but not exactly equivalent to a version of the file is called a delta Although technically a delta only includes the changes made in practice it is usual for each delta to be made with respect t
6. changes confict get will print an error the generated result should be carefully examined before the delta is made SCCS Introduction 10 12 4 A more detailed example The following technique might be used to maintain a different version of a program First create a directory to contain the new version mkdir newxyz cd newxyz Edit a copy of the program on a branch sccs d xyz edit prog c When using the old version be sure to use the b fhg to info check tell and clean to avoid confusion For example use sccs info b when in the directory xyz If you want to save a copy of the program still on the branch back in the s fi le you can use secs d xyz deledit prog c which will do a delta on the branch and reedit it for you When the experiment is complete merge it back into the s fi le using delta sccs d xyz delta prog c At this point you must decide whether this version should be merged back into the trunk i e the default version which may have undergone changes If so it can be merged using the i fhg to edit as described above 12 5 A warning Branches should be kept to a minimum After the first branch from the trunk SID s are assigned rather haphazardly and the structure gets complex fast 13 Using SCCS with Make SCCS and make can be made to work together with a little care A few sample makefi les for common applications are shown There are a few basic entries that eve
7. e flag to get as sccs get e prog c Keep this in mind when reading other documentation Yes this is a stupid default Changes to a line are counted as a line deleted and a line inserted SCCS Introduction 4 5 3 When to make deltas It is probably unwise to make a delta before every recompilation or test otherwise you tend to get a lot of deltas with comments like fixed compilation problem in previous delta or fixed botch in 1 3 However it is very important to delta everything before installing a module for general use A good tech nique is to edit the fi les you need make all necessary changes and tests compiling and editing as often as necessary without making deltas When you are satisfied that you have a working version delta everything being edited re get them and recompile everything 5 4 What s going on the info command To fi nd out what fi les where being edited you can use sccs info to print out all the files being edited and other information such as the name of the user who did the edit Also the command sccs check is nearly equivalent to the info command except that it is silent if nothing is being edited and returns non zero exit status if anything is being edited it can be used in an install entry in a makefile to abort the install if anything has not been properly deltaed If you know that everything being edited should be deltaed you can use sccs delta sccs tell The
8. file and then get that file This can be done by using sccs delget prog c which is entirely equivalent to using sccs delta prog c sccs get prog c The deledit command is equivalent to delget except that the edit command is used instead of the get command 8 2 Fix Frequently there are small bugs in deltas e g compilation errors for which there is no reason to maintain an audit trail To replace a delta use secs fi x r1 4 prog c This will get a copy of delta 1 4 of prog c for you to edit and then delete delta 1 4 from the SCCS file When you do a delta of prog c it will be delta 1 4 again The r fhg must be specifi ed and the delta that is specifi ed must be a leaf delta i e no other deltas may have been made subsequent to the creation of that delta 8 3 Unedit If you found you edited a fi le that you did not want to edit you can back out by using sccs unedit prog c 8 4 The d flag If you are working on a project where the SCCS code is in a directory somewhere you may be able to simplify things by using a shell alias For example the alias alias syssccs sccs d usr srce will allow you to issue commands such as syssccs edit cmd who c which will look for the file 7usr src emd SCCS who c The file who c will always be created in your SCCS Introduction 8 current directory regardless of the value of the d fhg 9 Using SCCS on a Project Working on a proj
9. get lt The trick here is that the DEFAULT rule is called every time something is needed that does not exist and no other rule exists to make it The explicit dependency of the o file on the c file is important Another way of doing the same thing is SRCS prog c prog h example c LDFLAGS i s prog prog o CC LDFLAGS o prog prog o prog o prog h example example o CC LDFLAGS o example example o sources SRCS SRCS sccs get There are a couple of advantages to this approach 1 the explicit dependencies of the o on the c files are not needed 2 there is an entry called sources so if you want to get all the sources you can just say make sources and 3 the makefi le is less likely to do confusing things since it won t try to get things that do not exist 13 2 To maintain a library Libraries that are largely static are best updated using explicit commands since make doesn t know about updating them properly However libraries that are in the process of being developed can be handled quite adequately The problem is that the o fi les have to be kept out of the library as well as in the library SCCS Introduction confi guration information OBJS a o b o c o d o SRCS a c b c c c d s x h y h z h TARG usr lib programs GET sccs get REL AR ar RANLIB ranlib lib a OBJS AR rvu lib a OBJS RANLIB lib a install lib a sccs check cp lib a TARG lib a
10. stated secs get c 80 07 22 12 00 00 prog c 6 2 Selectively deleting old deltas Suppose that you later decided that you liked the changes in delta 1 4 but that delta 1 3 should be removed You could do this by excluding delta 1 3 sccs edit x1 3 prog c When delta 1 5 is made it will include the changes made in delta 1 4 but will exclude the changes made in delta 1 3 You can exclude a range of deltas using a dash For example if you want to get rid of 1 3 and 1 4 you can use secs edit x1 3 1 4 prog c which will exclude all deltas from 1 3 to 1 4 Alternatively secs edit x1 3 1 prog c will exclude a range of deltas from 1 3 to the current highest delta in release 1 In certain cases when using x or i see below there will be conficts between versions for exam ple it may be necessary to both include and delete a particular line If this happens SCCS always prints out a message telling the range of lines effected these lines should then be examined very carefully to see if the version SCCS got is ok Since each delta in the sense of a set of changes can be excluded at will that this makes it most useful to put each semantically distinct change into its own delta 7 Auditing Changes 7 1 The prt command When you created a delta you presumably gave a reason for the delta to the comments prompt To print out these comments later use sccs prt prog c This will produce a report for
11. tell command is similar to info except that only the names of files being edited are output one per line All of these commands take a b flag to ignore branches alternate versions described later and the u flag to only give files being edited by you The u flag takes an optional user argument giving only fi les being edited by that user For example sccs info ujohn gives a listing of fi les being edited by john 5 5 ID keywords Id keywords can be inserted into your fi le that will be expanded automatically by get For example a line such as static char SccsId 7W t G will be replaced with something like static char SccsId prog c 1 2 08 29 80 This tells you the name and version of the source fi le and the time the delta was created The string is a special string which signals the beginning of an SCCS Id keyword 5 5 1 The what command To fi nd out what version of a program is being run use sccs what prog c usr bin prog which will print all strings it finds that begin with This works on all types of fi les including bina ries and libraries For example the above command will output something like prog c prog c 1 2 08 29 80 usr bin prog prog c 1 1 02 05 79 From this I can see that the source that I have in prog c will not compile into the same version as the binary SCCS Introduction 5 in usr bin prog 5 5 2 Where to put id keywords ID keywo
12. An Introduction to the Source Code Control System Eric Allman Project Ingres University of California at Berkeley This document gives a quick introduction to using the Source Code Control System SCCS The pre sentation is geared to programmers who are more concerned with what to do to get a task done rather than how it works for this reason some of the examples are not well explained For details of what the magic options do see the section on Further Information This is a working document Please send any comments or suggestions to csvax er ic 1 Introduction SCCS is a source management system Such a system maintains a record of versions of a system a record is kept with each set of changes of what the changes are why they were made and who made them and when Old versions can be recovered and different versions can be maintained simultaneously In projects with more than one person SCCS will insure that two people are not editing the same file at the same time All versions of your program plus the log and other information is kept in a file called the s file There are three major operations that can be performed on the s file 1 Geta file for compilation not for editing This operation retrieves a version of the file from the s file By default the latest version is retrieved This file is intended for compilation printing or whatever it is specifically NOT intended to be edited or changed in any way
13. RANLIB TARG lib a sources SRCS SRCS GET REL print sources pr h cs clean rm f o rm f core a out LIB The REL in the get can be used to get old versions easily for example make b o REL r1 3 12 The install entry includes the line Sccs check before anything else This guarantees that all the s files are up to date i e nothing is being edited and will abort the make if this condition is not met 13 3 To maintain a large program OBJS a o b o c o d o SRCS a c b c c y d s x h y h z h GET scces get REL a out OBJS CC LDFLAGS OBJS LIBS sources SRCS SRCS GET REL The print and clean entries are identical to the previous case This makefi le requires copies of the source and object fi les to be kept during development It is probably also wise to include lines of the form a o x h y h b o z h c o x h y h z h z h x h so that modules will be recompiled if header fi les change SCCS Introduction 13 Since make does not do transitive closure on dependencies you may find in some makefi les lines like z h x h touch z h This would be used in cases where fi le z h has a line include x h in order to bring the mod date of z h in line with the mod date of x h When you have a makefi le such as above the touch command can be removed completely the equivalent effect will be achieved by doing an automatic get on z h
14. a SCCS You will be prompted for comments only once 5 7 Creating new releases When you want to create a new release of a program you can specify the release number you want to create on the edit command For example secs edit r2 prog c will cause the next delta to be in release two that is it will be numbered 2 1 Future deltas will automati cally be in release two To change the release number of an entire system use secs edit r2 SCCS 6 Restoring Old Versions 6 1 Reverting to old versions Suppose that after delta 1 2 was stable you made and released a delta 1 3 But this introduced a bug so you made a delta 1 4 to correct it But 1 4 was still buggy and you decided you wanted to go back to the old version You could revert to delta 1 2 by choosing the SID in a get sccs get r1 2 prog c This will produce a version of prog c that is delta 1 2 that can be reinstalled so that work can proceed In some cases you don t know what the SID of the delta you want is However you can revert to the version of the program that was running as of a certain date by using the c cutoff fag For example SCCS Introduction 6 sccs get c800722120000 prog c will retrieve whatever version was current as of July 22 1980 at 12 00 noon Trailing components can be stripped off defaulting to their highest legal value and punctuation can be inserted in the obvious places for example the above line could be equivalently
15. each delta of the SID time and date of creation user who created the delta number of lines inserted deleted and unchanged and the comments associated with the delta For exam ple the output of the above command might be D 1 2 80 08 29 12 35 31 bill 2 1 00005 00003 00084 removed q option D 1 1 79 02 05 00 19 31 eric 1 0 00087 00000 00000 date and time created 80 06 10 00 19 31 by eric 7 2 Finding why lines were inserted To find out why you inserted lines you can get a copy of the file with each line preceded by the SID that created it sccs get m prog c You can then fi nd out what this delta did by printing the comments using prt To find out what lines are associated with a particular delta e g 1 3 use SCCS Introduction 7 sccs get m p prog c grep 1 37 The p fhg causes SCCS to output the generated source to the standard output rather than to a file 7 3 Finding what changes you have made When you are editing a fi le you can fi nd out what changes you have made using sccs diffs prog c Most of the diff fags can be used To pass the c fhg use C To compare two versions that are in deltas use secs sccsdiff r1 3 r1 6 prog c to see the differences between delta 1 3 and delta 1 6 8 Shorthand Notations There are several sequences of commands that get executed frequently Sccs tries to make it easy to do these 8 1 Delget A frequent requirement is to make a delta of some
16. ect with several people has its own set of special problems The main problem occurs when two people modify a file at the same time SCCS prevents this by locking an s file while it is being edited As a result files should not be reserved for editing unless they are actually being edited at the time since this will prevent other people on the project from making necessary changes For example a good scenario for working might be sccs edit a c g c t c Vi a c g c t c do testing of the experimental version secs delget a c g c t c sccs info should respond Nothing being edited make install As a general rule all source files should be deltaed before installing the program for general use This will insure that it is possible to restore any version in use at any time 10 Saving Yourself 10 1 Recovering a munged edit file Sometimes you may find that you have destroyed or trashed a file that you were trying to edit Unfortunately you can t just remove it and re edit it SCCS keeps track of the fact that someone is trying to edit it so it won t let you do it again Neither can you just get it using get since that would expand the Id keywords Instead you can say sccs get k prog c This will not expand the Id keywords so it is safe to do a delta with it Alternately you can unedit and edit the file 10 2 Restoring the s file In particularly bad circumstances the SCCS file itself may get munged The most comm
17. o all the deltas that have occurred before However it is pos sible to get a version of the fi le that has selected deltas removed out of the middle of the list of changes equivalent to removing your changes later 2 3 SID s or version numbers A SID SCCS Id is a number that represents a delta This is normally a two part number consisting of a release number and a level number Normally the release number stays the same however it is possible to move into a new release if some major change is being made Since all past deltas are normally applied the SID of the fi nal delta applied can be used to represent a version number of the fi le as a whole 2 4 Id keywords When you get a version of a file with intent to compile and install it e something other than edit it some special keywords are expanded inline by SCCS These Id Keywords can be used to include the current version number or other information into the file All id keywords are of the form x where x is an upper case letter For example I is the SID of the latest delta applied W includes the module name SID and a mark that makes it findable by a program and G is the date of the latest delta applied There are many others most of which are of dubious usefulness When you get a file for editing the id keywords are not expanded this is so that after you put them back in to the s fi le they will be expanded automatically on each new version
18. on way this happens is that it gets edited Since SCCS keeps a checksum you will get errors every time you read the file To fix this checksum use sccs admin z prog c 11 Using the Admin Command There are a number of parameters that can be set using the admin command The most interesting of these are fhgs Flags can be added by using the f fhg For example sccs admin fd1 prog c sets the d fhg to the value 1 This fhg can be deleted by using sccs admin dd prog c The most useful fags are Or given up and decided to start over SCCS Introduction 9 b Allow branches to be made using the b fhg to edit dSID Default SID to be used on a get or edit If this is just a release number it constrains the version to a particular release only i Give a fatal error if there are no Id Keywords in a file This is useful to guarantee that a version of the fi le does not get merged into the s fi le that has the Id Keywords inserted as constants instead of internal forms y The type of the module Actually the value of this fhg is unused by SCCS except that it replaces the Y keyword The tfile fag can be used to store descriptive text from file This descriptive text might be the docu mentation or a design and implementation document Using the t fhg insures that if the SCCS file is sent the documentation will be sent also If file is omitted the descriptive text is deleted To see the descriptive
19. ranch ilist Same as get xlist Same as get Merge a file gotten using edit back into the s file Collect comments about why this delta was made Remove a fi le that has been edited previously without merging the changes into the s fi le Produce a report of changes t Print the descriptive text e Print nearly everything Give a list of all fi les being edited b Ignore branches u user Ignore fi les not being edited by user Same as info except that nothing is printed if nothing is being edited and exit status is returned Same as info except that one line is produced per fi le being edited containing only the fi le name Remove all fi les that can be regenerated from the s fi le Find and print id keywords Create or set parameters on s fi les ifi le Create using fi le as the initial contents z Rebuild the checksum in case the fi le has been trashed fflag Turn on the flag dflag Turn off delete the flag SCCS Introduction 15 tfi le Replace the descriptive text in the s file with the contents of fi le If fi le is omitted the text is deleted Useful for storing documentation or design amp implementation docu ments to insure they get distributed with the s fi le Useful fags are b Allow branches to be made using the b fhg to edit dsID Default SID to be used on a get or edit i Cause No Id Keywords error message to be a fatal error rather than a warning t The module
20. rds can be inserted anywhere including in comments but Id Keywords that are compiled into the object module are especially useful since it lets you find out what version of the object is being run as well as the source However there is a cost data space is used up to store the keywords and on small address space machines this may be prohibitive When you put id keywords into header files it is important that you assign them to different vari ables For example you might use static char AccessSid 7W G in the file access h and static char OpsysSid 7W G in the file opsys h Otherwise you will get compilation errors because SccsId is redefi ned The problem with this is that if the header fi le is included by many modules that are loaded together the version number of that header fi le is included in the object module many times you may find it more to your taste to put id keywords in header fi les in comments 5 6 Keeping SID s consistent across files With some care it is possible to keep the SID s consistent in multi fi le systems The trick here is to always edit all files at once The changes can then be made to whatever fi les are necessary and then all fi les even those not changed are redeltaed This can be done fairly easily by just specifying the name of the directory that the SCCS files are in secs edit SCCS which will edit all fi les in that directory To make the delta use sccs delt
21. ry makefi le ought to have These are a out or whatever the makefile generates This entry regenerates whatever this makefile is supposed to regenerate If the makefile regenerates many things this should be called all and should in turn have dependencies on everything the makefi le can generate install Moves the objects to the final resting place doing any special chmod s or ranlib s as appropriate sources Creates all the source fi les from SCCS fi les clean Removes all cruft from the directory print Prints the contents of the directory The examples shown below are only partial examples and may omit some of these entries when they are deemed to be obvious The clean entry should not remove files that can be regenerated from the SCCS files It is suffi ciently important to have the source fi les around at all times that the only time they should be removed is when the directory is being mothballed To do this the command sccs clean can be used This will remove all fi les for which an s fi le exists but which is not being edited SCCS Introduction 11 13 1 To maintain single programs Frequently there are directories with several largely unrelated programs such as simple commands These can be put into a single makefi le LDFLAGS i s prog prog o CC LDFLAGS o prog prog o prog o prog c prog h example example o CC LDFLAGS o example example o example o example c DEFAULT sccs
22. sion 1 1 was retrieved and that it has 87 lines The file prog c will be created in the cur rent directory The fi le will be read only to remind you that you are not supposed to change it This copy of the file should not be changed since SCCS is unable to merge the changes back into the s file If you do make changes they will be lost the next time someone does a get 5 Changing Files or Creating Deltas 5 1 Getting a copy to edit To edit a source file you must fi rst get it requesting permission to edit it sccs edit prog c The response will be the same as with get except that it will also say New delta 1 2 You then edit it using a standard text editor Vi prog c 5 2 Merging the changes back into the s file When the desired changes are made you can put your changes into the SCCS file using the delta command sccs delta prog c Delta will prompt you for comments before it merges the changes in At this prompt you should type a one line description of what the changes mean more lines can be entered by ending each line except the last with a backslash Delta will then type 1 2 5 inserted 3 deleted 84 unchanged saying that delta 1 2 was created and it inserted five lines removed three lines and left 84 lines unchanged The prog c file will be removed it can be retrieved using get Actually the SID of the fi nal delta applied was 1 1 gt The edit command is equivalent to using the
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