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Show crontabs for all users
added echo "### Crontabs for $user ####"; to make clear whose crontab is listed.

List files
Shortcut to list files in the current path.

Use the builtin ':' bash command to increment variables
I just found another use for the builtin ':' bash command. It increments counters for me in a loop if a certain condition is met... : [arguments] No effect; the command does nothing beyond expanding arguments and performing any specified redirections. A zero exit code is returned.

List files with full path
This version is a bit more portable although it isn't extended as easily with '-type f' etc. On AIX the find command doesn't have -maxdepth or equivalent.

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"

Python extract json

Share your terminal session (remotely or whatever)
Force the user you want to watch doing things into doing his things in a screen session. Then simply attach yourself to that session with the command shown above. Works only if you are on the same machine, of course

a fast way to repeat output a byte
the speed is about 500MB/s on my machine. i think it's fast enough to output not too many bytes. while a C program may output 1GB per sencond on my machine. if the size is not the power of 512,you may change the bs and count in dd.

Convert a mp3 file to m4a
I use this to convert mp3 files to m4a files that can be used as ringtones on the iPhone. I've documented the process here: http://www.control-d.com/?p=60

Awk: Perform a rolling average on a column of data
Sometimes jittery data hides trends, performing a rolling average can give a clearer view.


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