Commands tagged GNU (3)

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Display the list of all opened tabs from Firefox via a python one-liner and a shell hack to deal with python indentation.
You have to do that before : $ cd ~/.mozilla/firefox/ Require bash. If you use something else, you may use $ echo | python Forked from ArkSeth python script.

Make a server's console beep when the network is down
This is like ping -a, but it does the opposite. It alerts you if the network is down, not up. Note that the beep will be from the speaker on the server, not from your terminal. Once a second, this script checks if the Internet is accessible and beeps if it is not. I define the Net as being "UP", if I can ping Google's public DNS server (8.8.8.8), but of course you could pick a different static IP address. I redirect the beep to /dev/console so that I can run this in the background from /etc/rc.local. Of course, doing that requires that the script is run by a UID or GID that has write permissions to /dev/console (usually only root). Question: I am not sure if the -W1 flag works under BSD. I have only tested this under GNU/Linux using ping from iputils. If anybody knows how portable -W is, please post a comment.

most used commands in history (comprehensive)
Most of the "most used commands" approaches does not consider pipes and other complexities. This approach considers pipes, process substitution by backticks or $() and multiple commands separated by ; Perl regular expression breaks up each line using | or < ( or ; or ` or $( and picks the first word (excluding "do" in case of for loops) note: if you are using lots of perl one-liners, the perl commands will be counted as well in this approach, since semicolon is used as a separator

Watch active calls on an Asterisk PBX
Only the number of calls nothing else.

save stderr only to a file
taken from http://www.unix.com/shell-programming-scripting/158311-how-tee-stderr.html " What does it mean? The redirection operator n>&m makes file descriptor n to be a copy of file descriptor m. So, whe are: - Opening a new file descriptor, 3, that is a copy of file descriptor 1, the standard output; - Making file descriptor 1 a copy of file descriptor 2, the standard error output; - Making file descriptor 2 to be a copy of file descriptor 3 (the "backup" of the standard output) in a short: we swapped the standard output and the standard error output. "

extract email adresses from some file (or any other pattern)
find all email addresses in a file, printing each match. Addresses do not have to be alone on a line etc. For example you can grab them from HTML-formatted emails or CSV files, etc. Use a combination of $...|sort|uniq$ to filter them.

Copy your ssh public key to a server from a machine that doesn't have ssh-copy-id
This one is a bit more robust -- the remote machine may not have an .ssh directory, and it may not have an authorized_keys file, but if it does already, and you want to replace your ssh public key for some reason, this will work in that case as well, without duplicating the entry.

list all files in a directory, sorted in reverse order by modification time, use file descriptors.
It's both silly, and infinitely useful. Especially useful in logfile directories where you want to know what file is being updated while troubleshooting.

port scan using parallel
It takes over 5 seconds to scan a single port on a single host using nmap $ time (nmap -p 80 192.168.1.1 &> /dev/null) real 0m5.109s user 0m0.102s sys 0m0.004s It took netcat about 2.5 minutes to scan port 80 on the class C $ time (for NUM in {1..255} ; do nc -w 1 -z -v 192.168.1.${NUM} 80 ; done &> /dev/null) real 2m28.651s user 0m0.136s sys 0m0.341s Using parallel, I am able to scan port 80 on the entire class C in under 2 seconds $ time (seq 1 255 | parallel -j255 'nc -w 1 -z -v 192.168.1.{} 80' &> /dev/null) real 0m1.957s user 0m0.457s sys 0m0.994s

Two command output
Summarize established connections after netstat output. Using tee and /dev/stderr you can send one command output to terminal before executing wc so you can summarize at the bottom of the output.


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