I wanted to know if there was any way to check the contents of a file before it was modified in linux.
As in suppose i have a file called example.cpp where i have a C++ code written in it. Now if i made some changes and saved it, is it possible to check the older example.cpp file without the changes made?
Thanks in advance
No it's not possible. Linux does not store versioned copies of files.
What you can do is store your source files in a source control system such as git, subversion or cvs. These provide full versioning of all files stored within their repositories.
The file system does not make backups or do versioning. However, some editors make backups before saving. At least Gedit saves a backup of example.cpp as example.cpp~.
There are two ways to accomplish your goal:
Use a versioning file system. Then what you want to do happens automatically.
Use a VCS, such as Subversion, Mercurial or Git, and commit after (resp. before) every change.
Related
To let you understand my problem, i must give some brief explanation about the way my client application works.
First, we create workspaces with allwrite set, this is because our programming language (PowerBuilder) does not writes directly to txt files, it writes to 'pbl' files, which are binary.
However we dont version pbl files and to be able to version each object inside a pbl we need to run some cmdcommand, which will output the classes within the pbl file to text files (one file per class), these text files is what Perforce must version.
The problem now is that the pbls are being listed as modified files (in fact they are), but we dont want them to be marked as modified.
I could put them in a ignore file, but there are some Pbls in the repository which must be synced.
I know i could specify in the ignore file to ignore Pbls except the Pbls which are in the repository, but then these specific pbls would keep showing up as modified files when i run a reconcile..
What i want is to have the PBL file exactly the way it was before running the reconcile, unopened by perforce but modified.
Its would be ok, if i could revert them without undoing its modifications...
Or if i could run a reconcilefor all the files, except the pbls.
Does anyone knows a way to do that? Thank you.
You can revert files without refreshing their content from the repository by running 'revert -k': http://perforce.com/perforce/doc.current/manuals/cmdref/p4_revert.html
Recently I was asked the following question in an interview.
Suppose I try to create a new file named myfile.txt in the /home/pavan directory.
It should automatically create myfileCopy.txt in the same directory.
A.txt then it automatically creates ACopy.txt,
B.txt then BCopy.txt in the same directory.
How can this be done using a script? I may know that this script should run in crontab.
Please don't use inotify-tools.
Can you explain why you want to do?
Tools like VIM can create a backup copy of a file you're working on automatically. Other tools like Dropbox (which works on Linux, Windows, and Mac) can version files, so it backs up all the copies of the file for the last 30 days.
You could do something by creating aliases to the tools you use for creating these file. You edit a file with the tools you tend to use, and the alias could create a copy before invoking a tool.
Otherwise, your choice is to use crontab to occasionally make backups.
Addendum
let me explain suppose i have directory /home/pavan now i create the file myfile.txt in that directory , immediately now i should automatically generate myfileCopy.txt file in the same folder
paven
There's no easy user tool that could do that. In fact, the way you stated it, it's not clear exactly what you want to do and why. Backups are done for two reasons:
To save an older version of the file in case I need to undo recent changes. In your scenario, I'm simply saving a new unchanged file.
To save a file in case of disaster. I want that file to be located elsewhere: On a different computer, maybe in a different physical location, or at least not on the same disk drive as my current file. In your case, you're making the backup in the same directory.
Tools like VIM can be set to automatically backup a file you're editing. This satisfy reason #1 stated above: To get back an older revision of the file. EMACs could create an infinite series of backups.
Tools like Dropbox create a backup of your file in a different location across the aether. This satisfies reason #2 which will keep the file incase of a disaster. Dropbox also versions files you save which also is reason #1.
Version control tools can also do both, if I remember to commit my changes. They store all changes in my file (reason #1) and can store this on a server in a remote location (reason #2).
I was thinking of crontab, but what would I backup? Backup any file that had been modified (reason #1), but that doesn't make too much sense if I'm storing it in the same directory. All I would have are duplicate copies of files. It would make sense to backup the previous version, but how would I get a simple crontab to know this? Do you want to keep the older version of a file, or only the original copy?
The only real way to do this is at the system level with tools that layer over the disk IO calls. For example, at one location, we used Netapps to create a $HOME/.snapshot directory that contained the way your directory looked every minute for an hour, every hour for a day, and every day for a month. If someone deleted a file or messed it up, there was a good chance that the version of the file exists somewhere in the $HOME/.snapshot directory.
On my Mac, I use a combination of Time Machine - which backs up the entire drive every hour, and gives me a snapshot of my drive that stretches back over a year and a half) and Dropbox which keeps my files stored in the main Dropbox server somewhere. I've been saved many times by that combination.
I now understand that this was an interview question. I'm not sure what was the position. Did the questioner want you to come up with a system wide way of implementing this, like a network tech position, or was this one of those brain leaks that someone comes up with at the spur of the moment when they interview someone, but were too drunk the night before to go over what they should really ask the applicant?
Did they want a whole discussion on what backups are for, and why backing up a file immediately upon creation in the same directory is a stupid idea non-optimal solution, or were they attempting to solve an issue that came up, but aren't technical enough to understand the real issue?
After few weeks of struggle i am able to create a medium native package debian package which works well in installation and removing of the package.
As http://www.quietsche-entchen.de/cgi-bin/wiki.cgi/-wiki/CreatingDebianPackages
Debian wiki
http://wiki.debian.org/HowToPackageForDebian http://www.debian.org/doc/manuals/maint-guide/ these are the quite good material for beginners,
I have basic problem, in updating the package all the files data.tar.gz are updated by default.
I want only few files to get updated in the data.tar.gz based on a key variable stored in all the files.
After the unpacking that is executing preinst script, all the files in data.tar.gz are already updated..
my idea was to take back up of the files intially before upgrading the package, and check key variable in files.. if the key variable is greater than the current variable replace it..
which means i am writing a simple backup script.. and executing in the postinst file..
i donot think this is good idea.. and more over limitations in dash script make it a very tough job..
What are you trying to accomplish here? During the reinstallation (or upgrading) of a Debian package, replacement of all of the non-conffiles with the latest version is exactly what's supposed to happen. If the file hasn't changed since the last installed version of the package then there's no harm in updating it anyway, and if is has changed, it's supposed to be updated.
If you have specific files which might be modified by the user and should be preserved across upgrades, make then conf files. The package system will prompt the user and ask them if they want to keep the package maintainer's version or the locally modified version.
(But if you're going to make every file a conf file, then you're probably doing something wrong.)
To make a file a conffile, list it in debian/conffiles. But if the file is going to be installed under /etc then you don't need to do this because dh_installdeb will do it for you.
EDIT following additional information in comment:
Suppose you have files test1.sh and test2.sh (among others) in your package. In the Debian world, they are either conffiles are intended to be modified by the end user, or they're not.
conffiles should be relatively few in number and as short as possible, to minimize the burden of having to reconcile changes made by the package maintainer with conflicting changes made by the end user.
If there are things mixed into the code that the end user is likely to want to tune, try to factor them out into a configuration file. If you put that file in /etc, you don't even have to manually designate it as a conffile.
If the end user needs to make a change to a non-conffile, they should use the dpkg-divert protocol to (1) move the original file aside, and (2) edit a copy. Diverted files are respected by package upgrades. The end user who uses dpkg-divert should be aware that things might break after upgrades as a result, because the package maintainer hasn't foreseen that these files would be modified by end users and the locally modified version might be incompatible with a newly upgraded version of a different file. dpkg-divert should be used carefully and sparingly.
I have a bunch of files that I've changed that I don't really want to commit, but I would like to back them up locally in case I would like to use them again. (Then I'll revert them.)
TortoiseSvn working status helps to view the modified files, but I want a way to save them all to a separate directory like Backups\, preferably with their folder heirararchy still in tact.
How can I do that?
UPDATE:
Apparently branching is the way to go.
But what I did was just copied the modified files paths to the clipboard (which is an option in tortoisesvn) then to a file, and created a program to copy them to a backup folder.
You can create a branch and commit those files only in that branch.
You can commit it inside a branch, so it doesn't affect your current 'trunk' or branch.
If you had a try with bazaar , that is compatible with SVN, there is a shelf command to temporarily store a set of modification and apply back them later.
in perforce, i have a pending list with some changed files. now i want to revert to the base, but without loosing my changes, so i want to back them up somewhere. like saving the DIFFs of each file. at a later time, i want to restore those changes and continue my work.
is this possible? if so, how?
thanks!
there is no need for external tools at all, assuming you are on a unix machine (or have a proper cygwin setup under Windows, haven't tested it.) The only caveat is that Perforce's p4 diff produces an output that is slightly incompatible with patch, therefore you need it to point to your unix diff-command. In your client-root you can do
P4DIFF=/usr/bin/diff p4 diff -du > pending-changes.patch
optional (if you want to revert the open files from the command-line, otherwise use p4v):
p4 revert `p4 opened|awk -F\# '{print $1}'`
Later you would open the files for edit (can be automated by extracting the affected files from the patchfile pending-changes.patch and then:
patch < pending-patches
Depending on your path-layout in your client-root, you have to use the -p#num option of patch to get the patch applied cleanly.
You should be able to do a shelve. It's a way of saving a changelist for future editing. The link below is a Python add-in for Perforce that implements shelve. Also, I know that Practical Perforce has a couple of ways to shelve current changes without an external script. I don't have the book in front of me but I'll try to update this question tonight when I do.
http://public.perforce.com/wiki/P4_Shelve
Linked to from P4Shelve, is P4tar which looks very useful, and does the operations on the client, rather than branching on the server.
Certainly I'll be looking into doing similar things soon.
See also this question:
Sending my changelist to someone else without checking in.
It's basically the same thing.
Create a branch of these files in some appropriate location
Check out the branch versions of the files you have edited
Copy the edited files over from the trunk and submit them
Revert the files on the trunk
Now you've got those "diffs" you wanted safely archived. When your ready to apply those changes later on, just integrate them back into the trunk.
This is what the Python script, that Brett mentioned, does. This is the way to do it manually without any special tools.