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Create a DOS floppy image
mount with: mount -t msdos -o loop ./floppy.img /tmp/mnt

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"

Mapreduce style processing
parallel can be installed on your central node and can be used to run a command multiple times. In this example, multiple ssh connections are used to run commands. (-j is the number of jobs to run at the same time). The result can then be piped to commands to perform the "reduce" stage. (sort then uniq in this example). This example assumes "keyless ssh login" has been set up between the central node and all machines in the cluster. bashreduce may also do what you want.

Mac OS X: remove extra languages to save over 3 GB of space.
This will get the job done in the most efficient way - spawning only one `rm` process. "On-the-fly" find data is displayed through `tee` and you should have plenty of time to ctrl-c if needed before it's too late. You may need to re-run this after major Software Updates. To leave more languages in, add more ``-and \! -iname "lang*"'' statements: $ sudo find / -iname "*.lproj" -and \! -iname "en*" -and \! -iname "spanish*" -print0 | tee /dev/stderr | sudo xargs -0 rm -rfv **Edit: note the 2nd sudo near the end of the pipeline - this is necessary.

Emptying a text file in one shot
Within vi allow to empty a text file in one shot

mp3 streaming

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" }

Exclude grep from your grepped output of ps (alias included in description)
Surround the first letter of what you are grepping with square brackets and you won't have to spawn a second instance of grep -v. You could also use an alias like this (albeit with sed): alias psgrep='ps aux | grep $(echo $1 | sed "s/^\(.\)/[\1]/g")'

Show current pathname in title of terminal
This helps to keep track of what is going on when you have several tabs open in your terminal. The title automatically changes when you change directories.

Set name of windows in tmux/byobu to hostnames of servers you're connected to
*I run this with byobu as as a custom status bar entry that runs every 10 seconds by putting it in a script here: $ .byobu/bin/10_update_windows There's no output to stdout, so nothing is displayed on the status bar. *Presumes that #{pane_title} is set to the hostname or prompt containing the host name. In my case, it's in this format: $ $USER@$HOSTNAME:$PWD The sed commands may need to be modified if your pane_title is different. *If you want to strip out a common part of a hostname, add the following before '| uniq' $ -e 's/[COMMON PART]//' I use that to strip out the domain of the servers I connect to, leaving the subdomain.


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