NAME
File::Revision - return a name of non-existing backup file with a revision idSYNOPSIS
#######
# Subroutine interface
#
use File::Revision qw(new_revision num2revision parse_options revision2num revision_file rotate);
($file_name, $next_revsion) = new_revision($file, @options);
($file_name, $next_revsion) = new_revision($file, \@options);
($file_name, $next_revsion) = new_revision($file, \%options);
$revision_letter = num2revision($revision_number);
$options = parse_options($file, @options);
$options = parse_options($file, \@options);
$options = parse_options($file, \%options);
$revision_number = revision2num($revision_letter;
$file_name = revision_file($revision_number, $options);
$file_name = rotate($file, @options);
$file_name = rotate($file, \@options);
$file_name = rotate($file, \%options);
#######
# Object interface
#
$self = 'File::Revision'; # or
$self = new $class; # where $class::@ISA contains 'File::Revision'
($file_name, $next_revsion) = $self->new_revision($file, @options);
($file_name, $next_revsion) = $self->new_revision($file, \@options);
($file_name, $next_revsion) = $self->new_revision($file, \%options);
$revision_letter = $self->num2revision($revision_number);
$options = $self->parse_options($file, @options);
$options = $self->parse_options($file, \@options);
$options = $self->parse_options($file, \%options);
$revision_number = $self->revision2num($revision_letter;
$file_name = $self->revision_file($revision_number, $options);
$file_name = $self->rotate($file, @options);
$file_name = $self->rotate($file, \@options);
$file_name = $self->rotate($file, \%options);DESCRIPTIONS
The File::Revision program modules provides the name of a non-existing file with a revision identifier based on the a file name $file. This has many uses backup file uses. There are no restrictions on the number of backup files or the time to live of the backup files.
A typical use would be to create a backup file for If the revised file passes does not pass all validity checks, use the backup file to replace or repair the revised file. This minimizes loses import data when revising files.
Better yet, create a temporary file, using one of the temp file name program modules. Revise the temp file. Once it passes all valitity checks, rename the original file to the backup file and rename the temp file to the original file. This allows full use of the original file until a validated revison is ready to replace it.
The File::Revision program module also supports limiting the backup files and delete the oldest once File::Revision reaches the rotation limit.
SUBROUTINES
new_revision
($file_name, $next_revsion) = new_revision($file, @options);The new_revision subroutine returns the name of a non-existing file by appending revision letters to the base name of a supplied file. The supplied file usually exists.
num2revsion
$revision = num2revsion($number)The num2revision is the inverse of revision2num as described below.
parse_options
$options = parse_options($file, @options);The parse_options subroutine pre-process the options and used internally by the other routines. The only external ues is as an input to the revision_file subroutine.
The rotate and new_revision subroutine embeds the revision in the $file input to produce the $file_name output as follows:
"$vol$dir$base$pre_revision$lead_revision$revision$ext"The $vol $dir $base $ext are obtained from the $file input but may be overrided by the options vol dir base ext. The $pre_revision is the pre_revision option and has a default of '-'. The $lead_revision comes in play when a the places option has a number. It contains just enough characters so that places revision is exactly
length(($lead_revision$revision")The lead_revision default to a '_' for drafing style letter revisions and '0' for numeric revisions.
options description
----------------------------------------------------------
base overide the $file_name base
dir overide the $file_name dir
ext overide the $file_name ext
lead_places fill for places
places the maximum places of the embedded revision
revision the lowest revision embedded in $file_name
(new_revision subroutine only)
rotate the highest revision embeded in $file_name
(rotate subroutine only)
vol overide the $file_name volrevision2num
$number = revision2num($revision)The revision2num subroutine converts a drawing revision letter(s) that complies to American industry, US DOD, and International drawing practices to a number, where 0 is the drawing release, 1 the 1st revision, 2 the 2nd revision and so forth.
The old DOD-STD-100C which itself cited a slew of American National Standards, may itself been superceded by an American National Standard. Anyway drawing revisions are pretty the same across commerical, military and national boundaries. The US Navy provides DOD-STD-100C free. However, comericalized American Nation Standards are not so generous. They do not have the American taxpayer to support their generosity.
DOD-Std-100C 5003.2, Drawing Practices, states
'5003.2 Revision Letters. Upper-case letters shall be used in alphabetical sequence. The letters "I", "O", "Q", "S', "X" and "Z" shall be omitted. When revisions are numberous enough to exhaust the alphabet the revision following Y shall be "AA" and the next "AB", the "AC", etc. Revision letters shall not exceed two characters. The first revision to a drawing shall be assigned the letter A. Release (initial issue) of a drawing does not constitute a need for a revision letter.'
The convention is to use rev - for the initial release. The requirement that the revision does not exceed two letters, maximum of 400 revisions, is not realistic for automation of drawings. The revision for index drawings that index large databases can easy exceed this very quickly.
During the development of software programs, there can easily be more than 400 builds. When this happens, for strcit compliance, the drawing had to be rolled over to a new drawing and start out with rev -. Isn't more sensible to allow more than two letters for revisions, especially since it is easy to convert revision letters into a number.
When using hard paper media, 400 revisions never exist. Management lowers the hammer about revision MN. They fire the development team and bring in a new one.
Once there was a software engineer (SE) working on a Laser Printer and the lead mechanical engineer (ME) came it and starting examining a part. The SE asked him why he was looking so intensely at that part. The ME replied that they where going to revise it. SE: "Whey are you revising it?" ME: "It is the only part that has not been changed." That is funny unless you are the manager paying for it.
The standard drawing revision conventions is an interesting number system with no symbol for zero (absence of a revision is zero) and is base 20. The Persians successfully argued that the lack of a zero makes the arith twisted back in what is now Iran, Iraq around 600 A.D. However, the drafing disciplines never went along with this concept. Maybe they feel a symbol for zero makes the arith twisted. Anyway with non-zero digit arith there are additions and subtractions of one to shift around numbers to line up with the computer arith which uses arith with a zero symbol.
Actually this is being unkind. The reason drafting uses letters is because they are trying to make it hard to confuse the drawing revision with the drawing number. Then again, the American drafting standards and Internationl drafting standards allow letters in the drawing number. In other words, do not tried to understand drafting standards or make sense out of them. Just live with them.
Take a look at a base 4 number system without zero.
digits 1 2 3 4
Weights zero base ten
16 4 1 number
--------------------------
0
1 1
2 2
3 3
4 4
1 1 5
1 2 6
1 3 7
1 4 8
2 1 9
2 4 12
3 1 13
3 4 16
4 1 17
4 4 20
1 1 1 21
base 10 non-zero digit
digits 1 2 3 4 5 6 7 8 9 A
Weights zero base ten
100 10 1 number
9A A 1
--------------------------
0
1 1
2 2
3 3
4 4
A 10
1 1 11
9 A 100
A 1 101
A A 110
1 1 1 111
A A A 1110
base 20 non-zero digit
1111111112
12345678901234567890
ABCDEFGHJKLMNPRTUVWY
non-zero digit
400 20 1 number
- 0
A 1
Y 20
A A 21
A Y 40
W Y 400
Y A 401
Y Y 420 revision_file
$file_name = revision_file($revision_number, parse_options($file, @options));The revision_file subroutine returns the backup file name for $file with the $revision_number embedded. This subroutine does not check to see if the $file_name exists. The rotate and new_revision subroutines use it extensively internally.
rotate
$file_name = rotate($file, @options);The rotate subroutine returns is similar to the new_file subroutine except that it uses rotate as the highest revision that will be embedded in $file_name. When the subroutine finds that the highest revision file exists, it unlinks the oldest revision and rotates the rest of the files by renaming them to the next lowest revision. The subroutine returns the a $file_name with the vacated rotate revision embedded in the name.
REQUIREMENTS
Someday.
DEMONSTRATION
#########
# perl Revision.d
###~~~~~~ Demonstration overview ~~~~~
The results from executing the Perl Code follow on the next lines as comments. For example,
2 + 2
# 4~~~~~~ The demonstration follows ~~~~~
use File::AnySpec;
use File::Package;
use File::Path;
use File::Copy;
my $fp = 'File::Package';
my $uut = 'File::Revision';
my ($file_spec, $from_file, $to_file, $backup_file, $rotate);
my $loaded = '';
##################
# Load UUT
#
my $errors = $fp->load_package($uut)
Cannot load File::Revision
Global symbol "%options" requires explicit package name at E:\User\SoftwareDiamonds\installation\lib/File/Revision.pm line 140.
Global symbol "%options" requires explicit package name at E:\User\SoftwareDiamonds\installation\lib/File/Revision.pm line 144.
Global symbol "%options" requires explicit package name at E:\User\SoftwareDiamonds\installation\lib/File/Revision.pm line 149.
BEGIN not safe after errors--compilation aborted at E:\User\SoftwareDiamonds\installation\lib/File/Revision.pm line 169.
Compilation failed in require at (eval 12) line 1.
# 'Cannot load File::Revision
# Global symbol "%options" requires explicit package name at E:\User\SoftwareDiamonds\installation\lib/File/Revision.pm line 140.
# Global symbol "%options" requires explicit package name at E:\User\SoftwareDiamonds\installation\lib/File/Revision.pm line 144.
# Global symbol "%options" requires explicit package name at E:\User\SoftwareDiamonds\installation\lib/File/Revision.pm line 149.
# BEGIN not safe after errors--compilation aborted at E:\User\SoftwareDiamonds\installation\lib/File/Revision.pm line 169.
# Compilation failed in require at (eval 12) line 1.
# '
#
##################
# revision2num('-')
# QUALITY ASSURANCE
Running the test script Revision.t verifies the requirements for this module.
The <tmake.pl> cover script for Test::STDmaker automatically generated the Revision.t test script, Revision.d demo script, and t::File::Revision STD program module POD, from the t::File::Revision program module contents. The t::File::Revision program module is in the distribution file File-Revision-$VERSION.tar.gz.
NOTES
Author
The holder of the copyright and maintainer is
<support@SoftwareDiamonds.com>
Copyright Notice
Copyrighted (c) 2002 Software Diamonds
All Rights Reserved
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