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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"

Clean apt-get and gpg cache and keys
Cleans apt-get and gpg cache and keys

Find the biggest files
Also: * find . -type f -exec ls -s {} \; | sort -n -r | head -5 * find . -type f -exec ls -l {} \; | awk '{print $5 "\t" $9}' | sort -n -r | head -5

Test I/O performance by timing the writing of 100Mb to disk
Write 200 blocks of 512k to a dummy file with dd, timing the result. The is useful as a quick test to compare the performance of different file systems.

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" }

while using lxde and being blinded by your laptop screen, you can type:
I'm not sure what apt this is, but it seems to work on most X screens, an is useful for saving power, and not straining your eyes

Run a script in parrallel over ssh
Runs a local script over ssh assuming ssh keys are in place. -P argument prints results to stdout. # Uses - https://code.google.com/p/parallel-ssh/

Retrieve "last modified" timestamp of web resource in UTC seconds
This command line assumes that "${url}" is the URL of the web resource. It can be useful to check the "freshness" of a download URL before a GET request.

Recursively Add Changed Files to Subversion
Extracted from http://www.howtogeek.com/wiki/Recursively_Add_Changed_Files_to_Subversion

Get the full path of a bash script's Git repository head.
Rather than complicated and fragile paths relative to a script like "../../other", this command will retrieve the full path of the file's repository head. Safe with spaces in directory names. Works within a symlinked directory. Broken down: $cd "$(dirname "${BASH_SOURCE[0]}")" temporarily changes directories within this expansion. Double quoted "$(dirname" and ")" with unquoted ${BASH_SOURCE[0]} allows spaces in the path. $git rev-parse --show-toplevel gets the full path of the repository head of the current working directory, which was temporarily changed by the "cd".


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