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Tag: readline

Readline shortcuts: Ctrl-s and XOFF

And another contribution to my list of Readline keyboard shortcuts. This time it’s a note by Joo Matos, pointing me to problems with the Ctrl-s shortcut. (It acts as a flow control character that pauses transmission on some terminals.)

He adds that:

It’s easy to disable special treatment of Ctrl-s by the terminal with stty -ixon.

Remember also that, if you accidentally hit Ctrl-s, it’s easy to undo the effects with Ctrl-q.

Thanks Joo!

Another contributed Readline keyboard shortcut

Last Wednesday, I was given a very nice response with a great tip to my table of Readline keyboard shortcuts by Luca City. Yesterday, Lance Levine gave me another extremely nice response and another great tip:

Just wanted to say appreciate the nice readline cheatsheet. There were a couple I never knew (the ctrl-alt-asterisk is gonna be a real time saver) and I never knew about ctrl-G or ctrl-J to end incremental searches either.

One that might be worth knowing for a lot of people if you ever make updates, would be the ctrl-x-x cmd. which takes you to the beginning of the line (and then back again if you hit it again). I enjoy working in screen, and the default ctrl-a escapes you from readline when you’re in a screen session so I never use it lest get confused.

Best Regards,
Lance Levine

Well, Lance, I’m an avid GNU screen user myself, so your tip is very useful to me! I’ve added it to the table to ease the suffering of our fellow GNU screen users. 🙂

Indeed I did, but I found it difficult to come up with a concise and clear description of the shortcut. So difficult, in fact, that I didn’t succeed at it:

Ctrl+x+x readline keyboard shortcut with ugly description

So, what does the Readline user manual have to say that may help me with a description?

exchange-point-and-mark (C-x C-x)
Swap the point with the mark. The current cursor position is set to the saved position, and the old cursor position is saved as the mark.

While typing, the mark normally is at the beginning of the line. Pressing Ctrl-x-x will move the cursor to the mark and set the mark to the old cursor position. If you now move the cursor and press Ctrl-x-x again, the mark won’t be at the beginning of the line but at place where you moved the cursor to. This means that the Ctrl-x-x shortcut is more than just a way to move back and forth between the beginning and ending of a line.

Another goody worth mentioning is the Ctrl-@ shortcut which will simply set the mark at the current cursor position or at the position specified by a numeric argument.

Now, I just need to think of a way to integrate these two Readline command bindings into the table without the descriptions taking up as many lines as this blog post. 😕 Any bright ideas, anyone?

Bypassing smart completion in Bash

Luca Citi, a nice Italian Ubuntu user, just gave me an excellent tip in response to my list of Readline keyboard shortcuts. Modern Linux distributions such as Ubuntu and Gentoo can easily be configured for Bash to use smart completion. With smart completion enabled, instead of just looking among all the available files and directories without discrimination, TAB will be able to more accurately adjust its list of available completions depending on the program for which arguments are being sought.

An example of smart completion is that completions for the cd command will only include actual directories and no longer any regular files. Luca gave me another good example: completions for the kpdf command will only include files with the .pdf extension.

Myself, I’ve been bitten by smart completion a few times because I’d want to complete a command argument towards a filename which wasn’t supported by the smart completion rules. Luca gave me his typical example of such a case: his smart completion configuration includes only entries from the fstab as valid mount points for the mount command. But, what if you want to do an ad-hoc mount? Will you just have to type out the full mount point without auto completion? That’s what I used to think before Luca told me about the Alt+/ shortcut. In Bash, this shortcut will act as the TAB-key would without smart completion enabled.

Of course, I’ve updated my list of Readline keyboard shortcuts to include Alt+/.Thanks Luca! 🙂

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