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Binary Clock
Binary clock with separate H:M:S.

Make a directory named with the current date
Create a directory named with the current date in ISO 8601 format (yyyy-mm-dd). Useful for storing backups by date. The --iso switch may only work with GNU date, can use format string argument for other date versions.

Convert string to uppercase

Sum columns from CSV column $COL
More of the same but with more elaborate perl-fu :-)

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" }

list block devices
Shows all block devices in a tree with descruptions of what they are.

Delete all but the latest 5 files
yes 6 (tail from 6th line)

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

urldecoding with one pure BASH builtin
You can use ordinary printf to convert "%23%21%2fbin%2fbash" into "#!/bin/bash" with no external utilities, by using a little known printf feature -- the "%b" specifier converts shell escapes. Replace % with \x and printf will understand the urlencoded string. BASH's printf has an extension to set a variable directly, too. So you get to convert urlencoded strings from garble to plaintext in one step with no externals and no backticks.

send tweets to twitter (and get user details)
great for outputting tweets from cron jobs and batch scripts


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