NAME
comb — combine SCCS deltas
SYNOPSIS
comb
[-p
SID]
[-c
list]
[-o]
[-s]
file ...
DESCRIPTION
The
comb
command generates a shell procedure (see
sh(1))
which, when run, reconstructs the given
SCCS
files.
The reconstructed files are usually smaller than the original files.
Arguments can be specified in any order,
but all options apply to all named
SCCS
files.
If a directory is named,
comb
behaves as though each file in the directory
were specified as a named file, except that non-SCCS
files (last component of the path name does not begin with
s.)
and unreadable files are silently ignored.
If a name of
-
is given, the standard input is read;
each line of the standard input is taken to be the name of an
SCCS
file to be processed; non-SCCS
files and unreadable files are silently ignored.
The generated shell procedure is written on the standard output.
Options
comb
recognizes the following options.
Each is explained as if only one named file is to be processed,
but the effects of any option apply independently to each named file.
- -pSID
The
SCCS IDentification
string
(SID)
of the oldest delta to be preserved.
All older deltas are discarded in the reconstructed file.
- -clist
A
list
of deltas to be preserved
(see
get(1)
for the syntax of a
list).
All other deltas are discarded.
- -o
For each
get -e
generated, this option causes the reconstructed file to be accessed
at the release of the delta to be created,
otherwise the reconstructed file would be accessed
at the most recent ancestor.
Use of the
-o
option can decrease the size of the reconstructed
SCCS
file.
It can also alter the shape of the delta tree of the original file.
- -s
This option causes
comb
to generate a shell procedure which, when run,
produces a report giving, for each file:
the file name, size (in blocks) after combining,
original size (also in blocks), and percentage change computed by:
100 × (original - combined) / original
It is recommended that this option be used before any
SCCS
files are actually combined to determine exactly
how much space is saved by the combining process.
If no options are specified,
comb
preserves only leaf deltas
and the minimal number of ancestors
needed to preserve the tree.
EXTERNAL INFLUENCES
International Code Set Support
Single- and multi-byte character code sets are supported.
EXAMPLES
The command:
comb -c1.1,1.3,1.6 s.document > save_file
creates a shell script named
save_file,
which if executed, creates a new
s.document
using only the deltas
1.1,
1.3,and
1.6
from the old
s.document.
The script overwrites the old
s.document;
thus, it might be wise to copy the original elsewhere.
Here is an example of typical technique:
cp s.document s.save
comb -c1.1,1.3,1.6 s.document > save_file
sh save_file
WARNINGS
comb
may rearrange the shape of the tree of deltas.
Combining files may or may not save space;
in fact, it is possible for the reconstructed file
to actually be larger than the original.
FILES
- s.COMB?????
Temporary file
- comb?????
Temporary file
