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1500 questions
439
votes
2 answers

How to list keys added to ssh-agent with ssh-add?

How and where can I check what keys have been added with ssh-add to my ssh-agent?
Patryk
  • 14,096
436
votes
9 answers

When should I not kill -9 a process?

I am always very hesitant to run kill -9, but I see other admins do it almost routinely. I figure there is probably a sensible middle ground, so: When and why should kill -9 be used? When and why not? What should be tried before doing it? What kind…
Mikel
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435
votes
4 answers

refresh changed content of file opened in vi(m)

I have a config-file that I keep open in vim, but that sometimes gets changed on disk, without these changes being reflected on the terminal. Can I refresh the content on the screen without closing and re-opening the file? If so, how?
twan163
  • 5,690
432
votes
21 answers

GPU usage monitoring (CUDA)

I installed CUDA toolkit on my computer and started BOINC project on GPU. In BOINC I can see that it is running on GPU, but is there a tool that can show me more details about that what is running on GPU - GPU usage and memory usage?
pbm
  • 25,387
431
votes
2 answers

Compress a folder with tar?

I'm trying to compress a folder (/var/www/) to ~/www_backups/$time.tar where $time is the current date. This is what I have: cd /var/www && sudo tar -czf ~/www_backups $time" I am completely lost and I've been at this for hours now. Not sure if…
qwerty
  • 4,451
430
votes
16 answers

In Bash, when to alias, when to script and when to write a function?

Noone should need 10 years for asking this question, like I did. If I were just starting out with Linux, I'd want to know: When to alias, when to script and when to write a function? Where aliases are concerned, I use aliases for very simple…
ixtmixilix
  • 13,230
428
votes
3 answers

What are the shell's control and redirection operators?

I often see tutorials online that connect various commands with different symbols. For example: command1 | command2 command1 & command2 command1 || command2 command1 && command2 Others seem to be connecting commands to files: command1 >…
terdon
  • 242,166
423
votes
9 answers

Remove all files/directories except for one file

I have a directory containing a large number of files. I want to delete all files except for file.txt . How do I do this? There are too many files to remove the unwanted ones individually and their names are too diverse to use * to remove them all…
Kantura
  • 4,705
418
votes
5 answers

Does curl have a timeout?

So far I couldn't find anything really, but is it true that curl doesn't really time out at all? user@host:~# curl http://localhost/testdir/image.jpg I'm asking because I'm redirecting any request for images in testdir to a separate Apache module…
Preexo
  • 4,763
417
votes
17 answers

How to do integer & float calculations, in bash or other languages/frameworks?

Using echo "20+5" literally produces the text "20+5". What command can I use to get the numeric sum, 25 in this case? Also, what's the easiest way to do it just using bash for floating point? For example, echo $((3224/3807.0)) prints 0 :(. I am…
Michael Durrant
  • 42,013
417
votes
13 answers

How can I find broken symlinks

Is there a way to find all symbolic links that don't point anywere? find ./ -type l will give me all symbolic links, but makes no distinction between links that go somewhere and links that don't. I'm currently doing: find ./ -type l -exec file…
gabe.
  • 11,784
416
votes
9 answers

How to get over "device or resource busy"?

I tried to rm -rf a folder, and got "device or resource busy". In Windows, I would have used LockHunter to resolve this. What's the linux equivalent? (Please give as answer a simple "unlock this" method, and not complete articles like this one.…
ripper234
  • 31,763
412
votes
15 answers

What are the pros and cons of Vim and Emacs?

How would you compare these editors? What are the pros and cons of each? [note] This is not meant to be answered by those who "hate one and love another" or those who haven't used both.
John Berryman
  • 755
412
votes
4 answers

Specify identity file (id_rsa) with rsync

I need to make periodic backups of a directory on a remote server which is a virtual machine hosted by a research organisation. They mandate that access to VMs is through ssh keys, which is all good, except that I can't figure out how to point rsync…
Jangari
  • 4,538
411
votes
4 answers

What characters do I need to escape when using sed in a sh script?

Take the following script: #!/bin/sh sed 's/(127\.0\.1\.1)\s/\1/' [some file] If I try to run this in sh (dash here), it'll fail because of the parentheses, which need to be escaped. But I don't need to escape the backslashes themselves (between…
detly
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