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Symlink all files from a base directory to a target directory
Simple and easy to remember, if it already exists then it just ignores it.

Debug bash shell scripts.
Display commands and their arguments as they are executed. Useful for debugging shell scripts.

Remind yourself to leave in 15 minutes
If you spend most of your time in front of the terminal, leave is a useful reminder. Leave can have absolute form: leave 1555 reminds you to leave at 3:55PM

Show the number of current httpd processes

Copy recursivelly files of specific filetypes
Copying only wmv and mpg files recursively from to

list files recursively by size

Switch all connected PulseAudio bluetooth devices to A2DP profile
Tries to switch all audio devices to the A2DP profile for optimal sound quality. Useful for bluetooth speakers and headphones that always power up in HSP/HFP mode. Note however that this command is only a shorthand for the GUI, so it cannot fix stubborn BT controllers that leave your device stuck in HSP mode until a manual re-coupling.

cd up a number of levels
Instead of typing "cd ../../.." you can type ".. 3". For extremely lazy typists, you can add this alias: alias ...=".. 2" ....=".. 3" - so now you can write just .... !!! NB the .. function needs to be "source"d or included in your startup scripts, perhaps .bashrc.

To print a specific line from a file
Just one character longer than the sed version ('FNR==5' versus -n 5p). On my system, without using "exit" or "q", the awk version is over four times faster on a ~900K file using the following timing comparison: $ testfile="testfile"; for cmd in "awk 'FNR==20'" "sed -n '20p'"; do echo; echo $cmd; eval "$cmd $testfile"; for i in {1..3}; do time for j in {1..100}; do eval "$cmd $testfile" >/dev/null; done; done; done Adding "exit" or "q" made the difference between awk and sed negligible and produced a four-fold improvement over the awk timing without the "exit". For long files, an exit can speed things up: $ awk 'FNR==5{print;exit}'

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" }


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