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1500 questions
105
votes
3 answers
What's the purpose of the randomart image for user (not host) SSH keys?
The ssh-keygen generates the following output:
The key fingerprint is:
dd:e7:25:b3:e2:5b:d9:f0:25:28:9d:50:a2:c9:44:97 user@machine
The key's randomart image is:
+--[ RSA 2048]----+
| .o o.. |
| o +Eo |
| + . |
| …
syntagma
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105
votes
6 answers
How to use a shell command to only show the first column and last column in a text file?
I need some help to figure out how to use the sed command to only show the first column and last column in a text file. Here is what I have so far for column 1:
cat logfile | sed 's/\|/ /'|awk '{print $1}'
My feeble attempt at getting the last…
user70573
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105
votes
3 answers
How to install dig on CentOS?
I can't find the dig command on my new CentOS installation. I've tried dnf install dig but it say that it cannot find the package.
How do I install dig on CentOS?
Mikael Dúi Bolinder
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104
votes
7 answers
How can I edit symlinks?
My basic understanding of a symlink is that it's a special file, a file that contains a string path to another file. The kernel's VFS abstracts a lot of that away but is there any reason why symlinks seem to be impossible to edit?
In other words:…
Oli
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104
votes
5 answers
Installing a .deb package on Arch - Is it possible?
The problem is simple - I have a .deb package and I want to install it on my Arch Linux. Is this possible? If yes, how?
BKC
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104
votes
5 answers
How to check if a user can access a given file?
*nix user permissions are really simple, but things can get messy when you have to take in account all the parent directory access before reaching a given file. How can I check if the user has enough privileges? If not, then which directory is…
Metalcoder
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104
votes
3 answers
What are character special and block special files in a unix system?
How are character special files and block special files different from regular files in a Unix-like system? Why are they called “character special” and “block special” respectively?
Geek
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104
votes
2 answers
What is the difference between interactive shells, login shells, non-login shell and their use cases?
Possible Duplicate:
Difference between Login Shell and Non-Login Shell?
I have been looking at /etc/profile. bash.bashrc to see how they are run, and notice that some are executed by non-login shells, some work with interactive shells etc.
What…
vfclists
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104
votes
13 answers
How can I remove duplicates in my .bash_history, preserving order?
I really enjoying using control+r to recursively search my command history. I've found a few good options I like to use with it:
# ignore duplicate commands, ignore commands starting with a space
export HISTCONTROL=erasedups:ignorespace
# keep the…
cwd
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104
votes
10 answers
How to do nothing forever in an elegant way?
I have a program which produces useful information on stdout but also reads from stdin. I want to redirect its standard output to a file without providing anything on standard input. So far, so good: I can do:
program > output
and don't do anything…
a3nm
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104
votes
6 answers
Can I set up system mail to use an external SMTP server?
Is it possible to set up system mail on a linux box to be sent via a different smtp server - maybe even with authentication? If so, how do I do this?
If that's unclear, let give an example. If I'm at the command line and type:
cat body.txt | mail -s…
cwd
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104
votes
3 answers
How to signal the end of stdin input
In Bash, I learned that the ending signal can be changed by here document. But by default how can I signal the end of stdin input?
I happened to find that with cat and chardet, their stdin inputs can be signaled as finished by Ctrl+D. But I seems…
Tim
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104
votes
4 answers
What is the difference between 'rm' and 'unlink'?
Assuming you know the target is a symbolic link and not a file, is there any difference between using rm and unlink to remove the link?
IQAndreas
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104
votes
12 answers
How to find out which interface am I using for connecting to the internet?
I have eth0 and wlan0 according to ifconfig and I can ping google.com.
How can I find out (with a normal user, not root) what interface is active, as in, what interface did the ping (or whatever, ping is not mandatory) use?
I am using Ubuntu 11.04…
LanceBaynes
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104
votes
5 answers
Differences between sed on Mac OSX and other "standard" sed?
I am having some issues in using an answer provided on this site for this question about a sed command to replace a blank line with two other lines of content, and it was brought up if the sed command on Mac OS (10.6.7 for me) is different. I don't…
Peter Grill
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