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back ssh from firewalled hosts
host B (you) redirects a modem port (62220) to his local ssh. host A is a remote machine (the ones that issues the ssh cmd). once connected port 5497 is in listening mode on host B. host B just do a ssh 127.0.0.1 -p 5497 -l user and reaches the remote host'ssh. This can be used also for vnc and so on.

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.

Get playlist for Livestream on YouTube

Non Numeric Check
use to execute a block of code only if $var is numeric

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" }

Swap a file or dir with quick resotre
This lets you replace a file or directory and quickly revert if something goes wrong. For example, the current version of a website's files are in public_html. Put a new version of the site in public_html~ and execute the command. The names are swapped. If anything goes wrong, execute it again (up arrow or !!).

Bypass with hexencoding, dump /etc/passwd

Set gnome wallpaper to a random jpg from the specified directory
Every time this is run it will change your background picture. For added fun Add some DBUS magic: . $HOME/.dbus/session-bus/`cat /var/lib/dbus/machine-id`-0 export DBUS_SESSION_BUS_ADDRESS and a crontab entry: */5 * * * * above_command_in_script.sh >/dev/null 2>/dev/null now wallpaper changes every 5 mins

backup directory. (for bash)

nohup that doesn't generate nohup.out
I'm sure this can be piped into another way. Please share!


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