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(cvsbook.info)CVS And Implied Arguments

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CVS And Implied Arguments
-------------------------

In each of the CVS commands so far, you may have noticed that no files
were specified on the command line.  We ran

     floss$ cvs diff

instead of

     floss$ cvs diff hello.c

and

     floss$ cvs update

instead of

     floss$ cvs update hello.c

The principle at work here is that if you don't name any files, CVS acts
on all files for which the command could possibly be appropriate.  This
even includes files in subdirectories beneath the current directory; CVS
automatically descends from the current directory through every
subdirectory in the tree.  For example, if you modified
b-subdir/random.c and a-subdir/subsubdir/fish.c, running update may
result in this:

     floss$ cvs update
     cvs update: Updating .
     M hello.c
     cvs update: Updating a-subdir
     cvs update: Updating a-subdir/subsubdir
     M a-subdir/subsubdir/fish.c
     cvs update: Updating b-subdir
     M b-subdir/random.c
     floss$

or better yet:

     floss$ cvs -q update
     M hello.c
     M a-subdir/subsubdir/fish.c
     M b-subdir/random.c
     floss$

Note: The -q flag is a less emphatic version of -Q.  Had we used -Q, the
command would have printed out nothing at all, because the modification
notices are considered nonessential informational messages.  Using the
lowercase -q is less strict; it suppresses the messages we probably
don't want, while allowing certain, more useful messages to pass
through.

You can also name specific files for the update:

     floss$ cvs update hello.c b-subdir/random.c
     M hello.c
     M b-subdir/random.c
     floss$

and CVS will only examine those files, ignoring all others.

In truth, it's more common to run update without restricting it to
certain files.  In most situations, you'll want to update the entire
directory tree at once.  Remember, the updates we're doing here only
show that some files have been locally modified, because nothing has
changed yet in the repository.  When other people are working on the
project with you, there's always the chance that running update will
pull some new changes down from the repository and incorporate them into
your local files.  In that case, you may find it slightly more useful to
name which files you want updated.

The same principle can be applied to other CVS commands.  For example,
with diff, you can choose to view the changes one file at a time

     floss$ cvs diff -c b-subdir/random.c
     Index: b-subdir/random.c
     ===================================================================
     RCS file: /usr/local/cvs/myproj/b-subdir/random.c,v
     retrieving revision 1.1.1.1
     diff -c -r1.1.1.1 random.c
     *** b-subdir/random.c   1999/04/18 18:18:22     1.1.1.1
     --- b-subdir/random.c   1999/04/19 06:09:48
     ***************
     *** 1 ****
     ! /* A completely empty C file. */
     --- 1,8 --
     ! /* Print out a random number. */
     !
     ! #include <stdio.h>
     !
     ! void main ()
     ! {
     !   printf ("a random number\n");
     ! }

or see all the changes at once (hang on to your seat, this is going to
be a big diff):

     floss$ cvs -Q diff -c
     Index: hello.c
     ===================================================================
     RCS file: /usr/local/cvs/myproj/hello.c,v
     retrieving revision 1.1.1.1
     diff -c -r1.1.1.1 hello.c
     *** hello.c     1999/04/18 18:18:22     1.1.1.1
     --- hello.c     1999/04/19 02:17:07
     ***************
     *** 4,7 ****
     --- 4,8 --
       main ()
       {
         printf ("Hello, world!\n");
     +   printf ("Goodbye, world!\n");
       }
     Index: a-subdir/subsubdir/fish.c
     ===================================================================
     RCS file: /usr/local/cvs/myproj/a-subdir/subsubdir/fish.c,v
     retrieving revision 1.1.1.1
     diff -c -r1.1.1.1 fish.c
     *** a-subdir/subsubdir/fish.c   1999/04/18 18:18:22     1.1.1.1
     --- a-subdir/subsubdir/fish.c   1999/04/19 06:08:50
     ***************
     *** 1 ****
     ! /* A completely empty C file. */
     --- 1,8 --
     ! #include <stdio.h>
     !
     ! void main ()
     ! {
     !   while (1) {
     !     printf ("fish\n");
     !   }
     ! }
     Index: b-subdir/random.c
     ===================================================================
     RCS file: /usr/local/cvs/myproj/b-subdir/random.c,v
     retrieving revision 1.1.1.1
     diff -c -r1.1.1.1 random.c
     *** b-subdir/random.c   1999/04/18 18:18:22     1.1.1.1
     --- b-subdir/random.c   1999/04/19 06:09:48
     ***************
     *** 1 ****
     ! /* A completely empty C file. */
     --- 1,8 --
     ! /* Print out a random number. */
     !
     ! #include <stdio.h>
     !
     ! void main ()
     ! {
     !   printf ("a random number\n");
     ! }

Anyway, as you can see from these diffs, this project is clearly ready
for prime time.  Let's commit the changes to the repository.