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Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Temporarily ignore mismatched SSH host key
This command will bypass checking the host key of the target server against the local known_hosts file. When you SSH to a server whose host key does not match the one stored in your local machine's known_hosts file, you'll get a error like " WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!" that indicates a key mismatch. If you know the key has legitimately changed (like the server was reinstalled), a permanent solution is to remove the stored key for that server in known_hosts. However, there are some occasions where you may not want to make the permanent change. For example, you've done some port-forwarding trickery with ssh -R or ssh -L, and are doing ssh user@localhost to connect over the port-forwarding to some other machine (not actually your localhost). Since this is usually temporary, you probably don't want to change the known_hosts file. This command is useful for those situations. Credit: Command found at http://linuxcommando.blogspot.com/2008/10/how-to-disable-ssh-host-key-checking.html. Further discussion of how it works is there also. Note this is a bit different than command #5307 - with that one you will still be prompted to store the unrecognized key, whereas this one won't prompt you for the key at all.

start a tunnel from some machine's port 80 to your local post 2001
now you can acces the website by going to http://localhost:2001/

Search some text from all files inside a directory

find all active IP addresses in a network
There are several other options. This one is plain and simple. Another option is: nmap -sP 192.168.0.0/24

Run remote web page, but don't save the results
I have a remote php file that I want to run once an hour. I set up cron to run this wget. I don't really care about what's in the file though, I don't want to save the results, so I run the -O and send it to /dev/null

Truncate 0.3 sec from an audio file using sox
Using this command one can cut a piece from the end of an audio file.

split a multi-page PDF into separate files
Have to do this once per output file, because if device is 'pdfwrite', even if 'gs' sees '%d' in the OutputFile it still only creates one single output file. Embed it into a simple shell script if you want to split a document out into one file for every page.

Advanced python tracing
Trace python statement execution and syscalls invoked during that simultaneously

Extract HTTP Passwords in POST Requests


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