I've noticed that sometimes commands can be tab completed.
e.g. the xm command in xen.
you type xm[space][tab] and it prints out the valid options
which are:
addlabel destroy info network-attach resume sysrq vnet-delete
block-attach dmesg labels network-detach rmlabel top vnet-list
block-detach domid list network-list save trigger vtpm-list
block-list domname loadpolicy new sched-credit unpause
cfgbootpolicy dry-run log pause sched-sedf uptime
console dump-core makepolicy reboot serve vcpu-list
create dumppolicy mem-max rename shutdown vcpu-pin
debug-keys getlabel mem-set resources start vcpu-set
delete help migrate restore suspend vnet-create
That's pretty slick!
How can I implement my own tab command completion in Linux?
This is a pretty broad question, but the general idea is that you register something with the either the compgen or complete builtin. They're both documented in the manual. The previous section documents the general topic of programmable completion, going through how completion attempts are processed.
For a whole ton of examples, see /etc/bash_completion, which provides all the default completion that comes with bash (beyond the totally built-in stuff like filename completion). For even more examples, see anything in /etc/bash_completion.d; those are automatically sourced by /etc/bash_completion as a way of extending the default completion.
This is done via the shell through the use of the GNU Readline library in the case of bash
bash's smart completion is handled by a series of scripted bash functions. On Debian, probably Ubuntu, and maybe other Linux distributions, you can find your system's installed completions in /etc/bash_completion.d.
The official documentation on this mechanism is at http://www.gnu.org/software/bash/manual/bash.html#Programmable-Completion
See this:
How does bash tab completion work?
and this:
http://www.debian-administration.org/articles/316
Related
I want to run following Linux command which opens the document with application registered with the system:
xdg-open mydocument.pdf
I see that many commands for this are available: run, run*, capture, shell, execute, system* etc.
from: http://wiki.call-cc.org/eggref/4/shell and https://wiki.call-cc.org/man/4/Unit%20utils
I also need the result of the command (ran successfully or not) from this.
Following (system without *), although not listed, also seem to work well:
(define result (system "xdg-open mydocument.pdf"))
Which of these will be the safest way to run system commands as above?
If the name of the document is hardcoded, it doesn't matter much what you use. If the file name is user-supplied, you must use qs to quote the arguments if you're relying on a string-based API like system's. It might be easier to pass arguments separately using process.
I don't know the shell egg very well, but if you want to get really fancy with shell calls, the scsh-process egg is a very nice alternative (full disclosure: I'm its author).
I am on windows machine, when I temporarily change to console using :sh then back to vim with exit command and then again back to console and it starts over. this causes me to lose my previous directory. Is there other way returning back to vim won't start the shell over?
Not really
https://stackoverflow.com/a/12089631/1427295
GVIM does not retain a "handle" to the shell that launched it in a way
that allows it to send commands back to it. Because of they
synchronous execution, you also cannot launch a shell from GVIM, keep
feeding it commands while also continue working in GVIM.
I'm afraid you have to use the functionality of your window manager to
launch (and then later re-activate) a shell window, and send the
commands as keystrokes to it. On Windows, this can be done (e.g. in
VBScript) via WshShell's Run(), AppActivate() and SendKeys() methods;
there are probably similar mechanisms for window control on Linux,
too.
If you don't mind having that shell inside your GVIM (emulated, with
all its drawbacks), though, there are plugins that enable that.
https://serverfault.com/a/95405
The Windows command interpreter ("cmd.exe") doesn't provide any
support for saving/exporting/keeping history, of, if it does,
Microsoft didn't document it and nobody was ever able to find it. You
can of course try to work around that, like Sean suggested, but
there's (or does appear to be) no built-in support for this
You may be able to output your command history using echo %cd% > prev_dir.txt then create a script that cds to the directory in prev_dir.txt, but you'd still have to remember to save your directory to the file before you exit the shell each time.
EDIT, the question might have not been totally clear, short version:
How to popup a dialog asking for user input if the script is running in the background and not in an active console?
/EDIT
When I run a bash script from udev or cron, it usually runs quietly somewhere in the background. Example could be plugging in an external harddrive runs rsync for data backup. So not every time I plug in the harddrive do I want to launch this action.
What is the most minimal way to fire up some user input dialog and ask yes or no? I could write some interface with PyQt but I want as little dependencies as possible, ideally cross window manager and maybe even without window manager.
Thanks!
EDIT 2: The lightweight (and hence as ugly as expected) version is xmessage, this would probably be the answer to the question, unless you have a better one:
xmessage "Do you want to run the backup script?" -buttons yes,no
http://linux.byexamples.com/archives/87/using-gui-dialog-box/
EDIT: So there's KDialog for kde, is there something really lightweight for X?
http://www.linux-magazine.com/Issues/2009/99/Zenity-and-KDialog
kdialog --title "Do you want to run the backup script?"
--yesno "Do you want to run the backup script?"
I'm currently leaning towards zenity, only trouble is it pulls in a whole array of gtk dependencies on kde, but is cross platform and works on windows. In essence, this is exaclty what I was looking for:
if zenity --question --text="Please press a button."; then
zenity --info --text="You pressed Yes\!"
else
zenity --error --text="You pressed No\!"
fi
But was hoping it would be a lot lighter on the resources / dependencies. Any alternative suggestions?
A simple approach would be for the automated script to simply email you, or perhaps alert with wall with instructions (containing the location of the real script).
Another approach would be for the automated script to touch a file in /var/lib and proceed if the file is still present after 5 minutes. This gives the user the option to stop the process (by removing the file), but maintains some automation.
This is not something you should have cron or udev handling in the first place. Write a userland daemon that listens for the appropriate D-Bus messages and performs the appropriate actions.
This should be post in linux or superuser or serverfault.
But, the number one google search on linux read user input links back here to StackOverflow:
https://www.google.com/search?q=linux+read+user+input&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=fflb
so I guess it's not too off base.
Again, the third or so google result for linux invoke command usb device plugin links to ServerFault:
https://serverfault.com/questions/399698/execute-a-command-when-a-device-is-connected-via-usb
I'll leave combining those two as an exercise.
I have implemented a simple linux shell in c. Now, I am adding some features and one I immediately thought about was to be able to show the last commands with the up arrow.
Question 1:
However, I have no idea how to accomplish this. Do you?
Question 2:
Any comment on how to store the "history" commands are also appreciated. I suppose something like a queue which allows access to all elements would be a good idea. Am I wrong? Do I have to implement it or is there already some good implementation out there I should know about?
Thanks.
Build libedit or readline support into your shell.
If you want to be lazy, you can use rlwrap:
rlwrap prog
I wrote the shell for HelenOS. Grab the bzr repo and navigate to uspace/app/bdsh (bdsh stands for the (b)rain (d)ead (sh)ell).
Other contributors have since added line editing / history / tab completion to the functions that handle input. Its written purely in ANSI C, does not link against glibc and implements its own functions. The code (both in the shell and underlying HelenOS libc) is 3 clause BSD, you can use it in anything.
If nothing else, it might help to just examine the implementation to get started.
I have some directories with a number of "hidden" files. One example of this is I'm in a source controlled sandbox and some of the files have not been checked out yet.
When I hit TAB, I'd like the option of seeing these files.
A similar question has been asked before: CVS Tab completion for modules under linux
The answers to that question summarize to: "Ubuntu's got that built in".
I don't have the option of switching to Ubuntu, but surely I can use the same mechanisms.
how can I hook into the TAB-completion feature of tcsh to add additional file Support for CVS, SVN and BitKeeper would all be useful.
More important than support for a specific source control system is the ability to control the returned list myself.
An acceptable solution would also be to use a key-binding other than TAB. (ctrl- perhaps)
From the manpage:
the complete builtin command can be used to tell the shell how to complete words other than filenames, commands and variables
might get you started
I do not know how to program in tcsh. But if you can, then you could look at the file named "bash_completion" from the archive (find the download link here.)
On line 1673 begins CVS completion code - and this might be portable to csh if you are familiar with the differences between bash/tcsh.
On my ubuntu machine, there is also a section for SVN completion (in /etc/bash_completion) that doesn't seem to be present in the maintainer's archive.
That's not Ubuntu-specific behavior, it's the bash-completion project.
You could use that, if you can switch from tcsh to bash.