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MULTIBAK: A Multiple Generation File Backup Utility Copyright 1989 Gilbert Shapiro ********** I. Purpose Many microcomputer programs that modify files, such as word processors, data base managers, and spreadsheets, provide for a single generation of backup, usually renaming the old version of "filename.ext" to "filename.bak" before writing a new "filename.ext" to disk. When a new revision is again saved, the old version again becomes "filename.bak," wiping out the backup file saved earlier. This is not always satisfactory. We may change our minds about a major change later, and want to return the document or the spreadsheet to its state several generations earlier. We may even discover much later a major error and the loss of earlier versions could seriously set our work back. For these reasons, some mainframe operating systems provide the option of multiple generations of backup. Not only the previous version of a file, but as many generations as the user wishes (or as many as can fit in his disk space) can be preserved. MULTIBAK is a set of programs intended to provide the most important features of such mainframe services for MSDOS systems. Any computer work that creates multiple changes in files can be made less frustrating and safer from disaster by using this collection of programs. When editing a document or developing a spreadsheet, for example, one might create a backup almost at the stroke of a key whenever significant changes are made, accumulating them until a final version is completed and verified. The backup files can then be conveniently erased using the PURGE program provided. II. Versions of MULTIBAK This is the freely distributed version of MULTIBAK. You are invited to make as many copies of this program as you wish for your own use or the use of others, for non-commercial purposes. You may not, however, charge anything for MULTIBAK (except for user groups, who may charge a cost-based fee, not to exceed $10, to cover their own costs). The free version of MULTIBAK consists of the following files: MULTIBAK.DOC This file. MBC.EXE The COPY model of MULTIBAK. MBR.EXE The RENAME model of MULTIBAK. PURGE.EXE A program for conveniently and safely erasing backup files. These programs comprise a fully functional system that will be sufficient for many users. A more elaborate system, with additional conveniences, is also available. If you send $20 to: CN Software, Dept. 185 414 S. Craig St., Suite 280 Pittsburgh, PA 15213 as a registered user of MULTIBAK you will receive a copy of an enhanced system, which includes 1. MEMORY RESIDENT versions of both the COPY and RENAME models. These make MULTIBAK available to the user at the touch of a Hot Key of his choice, permitting execution from within programs that do not provide facilities for the execution of DOS commands. 2. Two additional utilities: REVERT, which quickly and simply returns you to an earlier version of your file while preserving the current version, and RENUMBER, a facility to change a broken series of backup names to an unbroken series beginning at number one. III. General Functions of MULTIBAK MULTIBAK saves the current version of a file under a new file name; it is normally called immediately prior to issuing a "save" command to some program, such as a word processor, to write a new version. The name of the backup file is, by default, provided by MULTIBAK. Unless over-ridden by the user, by means described below, it is constructed as follows: - The drive, directory, and first file name are identical with the original file. - The extension is the first character of the extension of the original file, followed by the lowest integer from 1 to 99 not yet used in backup versions of that file. If the original file has no extension, the backup file extension will begin with a dash: for example, the first backup of MYFILE. will be MYFILE.-1, the second MYFILE.-2. Thus, if the file to be backed up is MYFILE.EXT, the first call to MULTIBAK will produce a backup file named MYFILE.E1, the second backup will be called MYFILE.E2, and so on. If, after the call to MULTIBAK, a new version is saved by a spreadsheet or word processor, it can always have the original name, MYFILE.EXT. Note that the preservation of the first letter of the original extension permits us to distinguish the backups of MYPROG.C, MYPROG.EXE and MYPROG.DOC, which will, respectively, have extensions beginning with C, E, and D. (The backups of MYFILE.BAS, MYFILE.BAT, and MYFILE.BAK will be jumbled together, however.) The COPY model, MBC.EXE, creates a new backup file by copying the current version, without disturbing the original. The RENAME model, MBR.EXE, on the other hand, calls upon DOS to rename the original, changing the name in the directory. Generally, these two procedures behave like the DOS commands with the same names, but with one exception: the RENAME model of MULTIBAK permits backups to appear in a directory different from the directory of the original file, which the DOS command does not. Like the DOS "copy" command, the COPY model of MULTIBAK permits backups to a different drive, while the RENAME model, like the rename command in DOS, does not. Like the DOS "copy" command, the COPY model of MULTIBAK keeps the original file intact, under its original name; like the "rename" command, the RENAME model does not, since it changes the file's name. On the other hand, long files can take considerably longer to back up using the COPY model, although they can be RENAMEd in an instant, and, in fact, as quickly as short files. IV. How to Use MULTIBAK In the following discussion, we will use the name MULTIBAK when we wish to describe commands or features common to both the COPY model, MBC.EXE, and the RENAME model, MBR.EXE. At a DOS prompt (such as "C>") MULTIBAK is called as follows: C>MULTIBAK filespec [backup filename root] [max files] (the arguments in square brackets, as usual, being optional). "Filespec" refers to the specification of the file to be backed up. It can be a "full" specification, including an optional drive and directory path. The "backup filename root," if provided, over-rides the default filename for backup files, which is described above (Section III). The rules for constructing this argument are provided below, Section V. "Max files," the final argument, specifies the maximum number of versions to be saved. That value can be any number up to 99. If this optional argument is provided, it over-rides the program default of 50. In case very large files are saved when disk space is at a premium, it might be set as low as 2 or 3. When plenty of disk space is available, or files are short and the recovery of earlier versions might be critical, a value of 99 makes sense. Since the program seeks the lowest integer available for a new backup by searching for existing files starting at the maximum and proceeding down, an unnecessarily large number might slightly slow execution. Note that "max files" can not be entered unless an explicit "backup filename root" is also entered: otherwise the number entered as the maximum number of files will be taken as the file name root. For example, on its first execution MBC MYFILE 10 will produce a backup of MYFILE named "10.-1". MBC MYFILE MYFILE 10 will produce what is desired, a backup named "MYFILE.-1" searching only from 10 to 1 instead of from 50 to 1 for already existing backup files. In all of the following examples, the file to be backed up is understood to be C:\SUBDIR\MYFILE.EXT. MBC.EXE and MBR.EXE are either in the current default directory or in the directory path. MULTIBAK means either MBC or MBR. 1. Succession of executions of COPY model, with default backup filenames. Command Files existing after command executed. ------- -------------------------------------- C>MBC MYFILE.EXT C:\SUBDIR\MYFILE.EXT C:\SUBDIR\MYFILE.E1 C>MBC MYFILE.EXT c:\subdir\MYFILE.EXT c:\subdir\MYFILE.E1 c:\subdir\MYFILE.E2 ****** 2. Succession of executions of RENAME model, with default backup filenames. Command Files existing after command executed. ------- -------------------------------------- C>MBR MYFILE.EXT C:\SUBDIR\MYFILE.E1 C>MBR MYFILE.EXT C:\SUBDIR\MYFILE.E1 C:\SUBDIR\MYFILE.E2 Note: Ordinarily, in this case, another program such as a word processor would create a new version of MYFILE.EXT when MULTIBAK creates a backup. ***** 3. Backup to a different directory. Command Files existing after command executed. ------- -------------------------------------- C>MBC MYFILE.EXT \ALTDIR\MYFILE C:\SUBDIR\MYFILE.EXT C:\ALTDIR\MYFILE.E1 or C>MBR MYFILE.EXT \ALTDIR\MYFILE C:\ALTDIR\MYFILE.E1 ***** 4. Backup to a different drive. Command Files existing after command executed. ------- -------------------------------------- C>MBC MYFILE.EXT D:\ANYDIR\MYFILE C:\SUBDIR\MYFILE.EXT D:\ANYDIR\MYFILE.E1 ***** 5. Backup to a new backup filename. Command Files existing after command executed. ------- -------------------------------------- C>MULTIBAK MYFILE.EXT BACKFILE C:\SUBDIR\MYFILE.EXT C:\SUBDIR\BACKFILE.E1 ***** 5. Backup using the same filename, to a different drive and directory. Command Files existing after command executed. ------- -------------------------------------- C>MBC MYFILE.EXT D:\ANYDIR\MYFILE C:\SUBDIR\MYFILE.EXT D:\ANYDIR\MYFILE.E1 NOTE: In this example, the explicit filename MYFILE may NOT be omitted in specifying the backup filename, even though it may be omitted when calling the DOS COPY program. V. The Backup Filename Root The "backup filename root," if provided, over-rides the default filename for backup files. It is called a "root" since an extension including a sequence number is appended to it to construct the full backup filename. The filename root: MUST include a first name for the backup file; MAY include a directory path; MUST NOT include an extension. If one is entered, it is ignored. The extension will always be assigned by the program, by the rules described above. The rule on including a drive in the backup filename root differs for the COPY and the RENAME models. You MAY include ANY drive when executing the COPY model. You MUST include the same drive if any is named in "filespec," i.e., the drive of the original file, when executing the RENAME model. For example: C>MBR D:\SUBDIR\FILE.EXT D:\NEWDIR\BACKUP is a correct command line entered from the current default disk C:, which would rename the current version of FILE.EXT in directory \SUBDIR of disk D: to one of BACKUP.E1, BACKUP.E2, BACKUP.E3, etc. (using the first unused integer) in directory \NEWDIR of disk D:. If the second "D:" is omitted, C>MBR D:\SUBDIR\FILE.EXT \NEWDIR\BACKUP the command will be interpreted as an attempt to backup a file located on D:, by renaming, to drive C:, the default drive, and the error message "Can not back up to a different drive" will appear on the screen. On the other hand, C>MBC D:\SUBDIR\FILE.EXT \NEWDIR\BACKUP using the COPY version, will create the backup file demanded: C:\NEWDIR\BACKUP.E?? where ?? represents a sequence number. VI. PURGE PURGE permits the deletion of selected generations of backup files created by MULTIBAK. Particularly when files are long, storing many generations could use considerable disk space to little purpose. But the chore of erasing large numbers of backups might be burdensome, since wild cards would probably wipe out useful files, including the current version. PURGE permits the user to select the generations to be erased with a single command. On each execution of MULTIBAK, the user is advised of the size in bytes and the serial number of the new backup, so that he can use the purge facility when he feels the number of backups is becoming excessive. PURGE is called at the DOS prompt as follows: C>PURGE [filename] [highest sequence number] [starting sequence number] where the "filename" is the name of the file whose backups are to be erased, including an optional drive, directory, and extension. The "highest sequence number" option permits erasing only the oldest generations, up to the specified number. Thus, if a file has 12 generations of backup on disk it is possible to erase, for example, the first six, or the first eleven. The second argument to PURGE, the starting sequence number, permits still more flexibility, the erasing of only the generations beginning at the number entered. Thus, if a file named "PROGRAM.C" has been backed up 8 times the directory will show: PROGRAM.C1 PROGRAM.C2 PROGRAM.C3 PROGRAM.C4 PROGRAM.C5 PROGRAM.C6 PROGRAM.C7 PROGRAM.C8 After execution of C:>PURGE PROGRAM.C 6 3 the disk will hold: PROGRAM.C1 PROGRAM.C2 PROGRAM.C7 PROGRAM.C8 If, as in this case, the sequence is broken, C>PURGE PROGRAM.C will erase files only until it finds a missing backup, i.e., in this case, it will erase PROGRAM.C1 and PROGRAM.C2. If, however, an upper limit is given as an argument to the command line all files up to that limit will be erased, regardless of missing versions. Thus, all files in the broken list above will be deleted by the command C>PURGE PROGRAM.C 8. These rules present an apparent danger to any file with an extension composed exclusively of two digits. When MULTIBAK backs up a file called FILE.12 its first backup will be called FILE.11, and its second backup will be called FILE.13. (If FILE.12 exists, it will skip that name.) Now the original file, FILE.12, appears to the computer as it does to a human observer as indistinguishable from a backup, and the command PURGE FILE.12 would seem to destroy the current version, FILE.12, along with its backups. PURGE, however, is programmed to avoid this; it will never erase the current version entered as its first argument on the command line. Examples of the Use of PURGE ============================ Erasing all backup files: PURGE MYFILE Files existing before command Files existing after command ============================= ============================ MYFILE.EXT MYFILE.EXT MYFILE.E1 MYFILE.E2 MYFILE.E3 Erasing all backups except the most recent: PURGE MYFILE 2 Files existing before command Files existing after command ============================= ============================ MYFILE.EXT MYFILE.EXT MYFILE.E1 MYFILE.E3 MYFILE.E2 MYFILE.E3 Erasing all except the first two backups: PURGE MYFILE 4 3 Files existing before command Files existing after command ============================= ============================ MYFILE.EXT MYFILE.EXT MYFILE.E1 MYFILE.E1 MYFILE.E2 MYFILE.E2 MYFILE.E3 MYFILE.E4 VII. Executing MULTIBAK from Other Programs While MULTIBAK can be called from the DOS prompt like any other program, it is specifically designed to be called from within applications that write modifications to files and provide either a DOS command call facility or a DOS Shell option. For example, SPRINT is an editor that, like many others, provides a macro, "call," that executes a DOS command. The following macro can be bound to a function key, so that it executes each time that key is pressed: call MBR fname write fname This stores the current version of the file being edited (SPRINT calls it "fname") without destroying previous backup versions, and then writes the newly edited version to disk, under the original file name. This backup procedure is very fast, and can be called a dozen times or more in a given editing session, so as to provide the possibility of returning to many different versions if desired. At the end of an editing session, some or all of these backups can be PURGEd. The popular word processor Word Perfect offers a different method of using MULTIBAK while editing. Instead of a macro for executing a DOS command, Word Perfect offers a "shell" command. Pressing Control-F1, the user sees a DOS prompt, which enables him to execute any DOS command including MBR or MBC. VIII. Disclaimer Used properly, this software will perform as described. By using this software, you acknowledge that this software may not suit your particular requirements or be completely trouble-free. We are not responsible for your specific application or any problems resulting from use of this software. We have no liability to you or any other person or entity for any damage or loss, including special, incidental, or consequential damages, caused by this software, directly or indirectly. Some states do not allow the limitation or exclusion of liability for incidental or consequential damages, so the above limitation or exclusion may not apply to you. ----------------end-of-author's-documentation--------------- Software Library Information: This disk copy provided as a service of The Public (Software) Library We are not the authors of this program, nor are we associated with the author in any way other than as a distributor of the program in accordance with the author's terms of distribution. Please direct shareware payments and specific questions about this program to the author of the program, whose name appears elsewhere in this documentation. If you have trouble getting in touch with the author, we will do whatever we can to help you with your questions. All programs have been tested and do run. To report problems, please use the form that is in the file PROBLEM.DOC on many of our disks or in other written for- mat with screen printouts, if possible. 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