How to undo linux

Best Answer: How do I undo changes in Linux?

Type u to undo the last change. To undo the last two changes, you must type 2u. Press Ctrl-r to redo the changes that were undone.

Is there an undo command in Linux?

There is no undo on the command line. However, you can run commands like rm -i and mv -i .

What is the command to undo the changes?

Try Git checkout – to discard uncommitted changes to a file. Git reset —hard is for when you want to discard all uncommitted changes. Use Git reset —hard to point the repository to a previous commit.

How do I undo changes in Ubuntu?

You cannot directly undo a command. Unfortunately, Linux does not support this feature. You can use command history to list all the previous commands you used. You need to find the reverse command for all of them (for example, if you called a sudo apt-get install command, you need to call sudo apt-get purge).

How do I undo a previous command?

To reverse your last action, press CTRL+Z. You can reverse more than one action. To revert your last undo, press CTRL+Y.

How do I undo a delete on Linux?

Short answer: you can’t. rm delete files blindly, without concept of ‘garbage’. Some Unix and Linux systems try to limit its destructiveness by aliasing rm -i by default, but not all do.

How can I undo on Unix?

Unix does not natively provide an undo function.. The philosophy is that if it’s gone, it’s gone. If it was important, it should have been backed up. Instead of deleting a file, you can move it to a temporary «trash» directory.

How do I undo a local change?

1. To overwrite local changes: git checkout —
2. To save local changes so you can reuse them later: git stash.
3. To discard local changes to all files, permanently: git reset –hard.

How do I undo a git push change?

1. Go to Git history.
2. Right-click the commit you want to roll back.
3. Select reverse commit.
4. Make sure Commit Changes is checked.
5. Click revert.

How do you undo an error?

The Undo function is most commonly found in the Edit menu. Many programs have an Undo button on the toolbar that usually looks like a curved arrow pointing to the left, like this one in Google Docs. Ctrl+Z (or Command+Z on a Mac) is a common keyboard shortcut for Undo.

How do I undo insert mode?

But there is a better way: Pressing while in insert mode, it will undo everything you’ve entered on the current line and leave you in insert mode. Just saved replacing 3 keystrokes with a single key combination.

What is revert in Ubuntu?

Note: git revert is used to log some new commits to reverse the effect of some previous commits (often just one faulty). If you want to discard all uncommitted changes to your working directory, you should see git-reset(1), particularly the —hard option.

How do I backup my entire Ubuntu?

How to make a backup in Ubuntu

1. With Deja Dup open, go to the Summary tab.
2. Press Back Up Now to get started.
3. Various software packages may require installation. …
4. Ubuntu backup prepares your files. …
5. The utility prompts you to secure the backup with a password. …
6. The backup runs for a few more minutes.

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Is there an «undo» command on the Unix comand line?

I get the feeling I’m going to need it one day, like if I’ve just deleted something I shouldn’t have, or renamed something and can’t remember what it should be called, etc.

No OS that I know of supports such a feature. To be able to support undo for a rm -Rf / would require that there be a complete backup of the drive in existence somewhere. This is never going to be possible (or desired due to the immense time maintaining these types of backups would take). That’s just one thing that one program could do; never mind undo for something like mke2fs /dev/hdb1 .

Ah, I got here thinking more along the lines of undoing a paste (or text entered at the command line), e.g. askubuntu.com/questions/444966/…

3 Answers 3

Negative. There is no magic undo button in Linux.

But if you screw something up with a typo, you can frequently use the command history to find out what you actually did as opposed to what you thought you did.

Unix doesn’t natively provide an undo feature. The philosophy is that if it’s gone, it’s gone. If it was important, it should have been backed up.

Instead of removing a file, you can move it to a temporary “trash” directory. Some desktop environments make their “delete” command move the file to the trash. But beware that only a few applications will use it; others will just remove the file.

Many commands can be reversed, e.g., a file move can be undone by moving the file back. Commands that delete or overwrite a file can’t easily be undone if at all; some of them can be made more robust against accidental data loss through shell settings. In particular:

On the command line, cp and mv will overwrite any existing target file, but you can make them prompt:

alias cp='cp -i' alias mv='mv -i' 

There is a FUSE filesystem that automatically keeps copies of old versions: copyfs, available for most unices (*BSD, Linux, OS X, Solaris). Of course, that can use a lot of resources.

If you’ve moved a file to a different directory and remember (part of) its name but not its location, you can use the locate command to find it.

The best way to protect against such accidents is to use a version control system (cvs, bazaar, darcs, git, mercurial, subversion, . ). It takes a little time to learn, but it pays off awesomely in the medium and long term.

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How to undo changes in the commands-history?

In UNIX systems you can press top and bottom arrows to navigate through the previous commands. This is extremely handy. Sometimes, I go up and find a command that I want to use again, but with some variations. If I do such changes, then I don’t have a way to get the original command back, unless I check it in history . Is there any way to «undo» the changes to the command in the history accessed through keys? My current workaround is to prepend a # to the command. This way the current command is performed as a comment, so nothing happens. Then, I can browse again through the commands with the keys. The problem is that the command I was using may be veeeery far away in the list, so going up again two hundred times is a bit . Control + R is not a solution either, since I may not remember exactly what I was looking for.

Example

My environment

$ echo $SHELL /bin/bash $ echo $TERM xterm 

That the command history is changed is likely a (mis-)feature of the shell you are using. In ksh , for example, you can edit history entries and invoke them without deleting the «previous version» of the entry; you have all invoked commands available.

With «it changes» I mean that: given a previous command that I changed after reaching it with the arrows, if I go up and down with the arrows, the old command won’t show the way it was, but the way I modified it. Of course, if I type «enter» performing a command, that old command will be as it was initially; but this is precisely what I am trying to avoid and looking for a way to «reset» the command to its initial value.

Also in this case, ksh ‘s behaviour differs here, it seems. And your history edit options also depend on the choosen editing mode. In ksh ‘s vi-mode, for example, the old entry is not overwritten, and I can also issue an undo command, like in vi , with ‘u’.

Uhms, this sounds very promising. I am now working in Bash and currently not considering to change to ksh , but it is good to know such thing exists there.

I’d like to know where bash stores recent command history before writing to the history file when the shell is closed. It may help in determining if this is possible. Anybody? I thought it might be in a one of the shell variables, but don’t have time to pore over the manual right now.

3 Answers 3

As long as you’ve edited a history entry but not pressed Enter yet, to go back to the original entry, repeatedly press Ctrl + _ — the undo command — until it doesn’t make any further change. You’re back to the original entry.

@MarkJeronimus No, it doesn’t, not from bash’s perspective. Maybe your terminal emulator converts Ctrl+- to Ctrl-_ — but that would be specific to your keyboard layout, and not all terminal emulators do this.

Ah you’re right. It works different in different terminals. gnome-terminal zooms out with Ctrl + — whereas xfce4-terminal undos

Revert to the original command when you’ve have made multiple changes to the line:

revert-line (M-r) Undo all changes made to this line. This is like executing the undo command enough times to get back to the beginning. 

M is the meta key, which is alt

Gratuitous, Yet Helpful Info

When you have executed a command like OP had previously done (it happens), there is nothing to «undo» because the commands are handled and remembered by the GNU Readline library and are not written to $HISTFILE until the shell exits. The reason I mention this is because you can’t just grep the $HISTFILE like one might expect and it may not be ideal to exit the shell.

So here are a couple of options to save you from scrolling back through all previous readline commands.

If you remember some of the command, press ctrl + r and type what you remember to search through previous commands containing that string. Pressing ctrl + r again will display the next most recent, searching backwards.

For example, type ls -l then ctrl + r as many times as it takes to find the previous command you seek. If you scroll past it, ctrl +s will search forward from the current position.

The fc bash builtin command is helpful to list the index numbers alongside previous readline commands.

fc -l -100 will list the previous 100 commands in readline.

Additionally, if OP knows he’s looking for a previous ls -l command, he could pipe the output to grep such as: fc -l -100 | grep ‘ls -l’

This should output a list of previous ls -l commands preceded by an index number. The output looks like this:
2065 ls -l

Now you can use the event designator !n where n is the index number. In this example, executing !2065 will expand to ls -l .

Although it doesn’t help after the fact, anyone looking to preserve the recent command history when modifying previous commands should see the HISTORY EXPANSION section of man bash . Here are some alternative methods for modifying old commands without overwriting the history.

The Event Designators section shows how you can easily edit string from the most recently used command.

^string1^string2^ Quick substitution. Repeat the previous command, replacing string1 with string2. Equivalent to ``. s/string1/string2/'' (see Modifiers below). 

$ echo foo foo $ ^foo^bar echo bar bar 

The most recent commands will now show:

The above example also explains how to use sed to replace a string in an event designator.

!-n Refer to the current command minus n. 

So if 3 commands up in the history is echo foo then you would use:
!-3:s/foo/bar

Note that event designators will appear in your history as the command executed, in this case echo bar . It will not appear in the history as !-3:s/foo/bar .

Just throwing that out there as it seems closely related, even if it is more of a «don’t do» than the «undo» solution OP is looking for.

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