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List files older than one year, exluding those in the .snapshot directory
Useful when you want to cron a daily deletion task in order to keep files not older than one year. The command excludes .snapshot directory to prevent backup deletion. One can append -delete to this command to delete the files : $ find /path/to/directory -not \( -name .snapshot -prune \) -type f -mtime +365 -delete

List all symbolic links in a directory matching a string
Finds all symbolic links in the specified directory which match the specified string pattern. I used this when upgrading from an Apple-supported version of Java 6 (1.6.0_65) to an Oracle-supported version (1.7.0_55) on Mac OS X 10.8.5 to find out which executables were pointing to /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands (Apple version) vs. /Library/Java/JavaVirtualMachines/jdk1.7.0_55.jdk/Contents/Home/bin (Oracle version). However, it appears the current JDK installation script already takes care of modifying the links.

Wait for an already launched program to stop before starting a new command.
Referring to the original post, if you are using $! then that means the process is a child of the current shell, so you can just use `wait $!`. If you are trying to wait for a process created outside of the current shell, then the loop on `kill -0 $PID` is good; although, you can't get the exit status of the process.

Multi line grep using sed and specifying open/close tags
Working with log files that contains variable length messages wrapped between open and close tags it may be useful to filter the messages upon a keyword. This works fine with GNU sed version 4.2 or higher, so pay attention to some unix distros (solaris, hp-ux, etc.). Linux should be ok.

processes per user counter
use Linux ;)

Get the IP address of a machine. Just the IP, no junk.
Why use many different utilities all piped together, when you only need two?

Enable programmable bash completion in debian lenny
The really awesome bash completion in debian seems to be an extra package now, which has to be installed. After sourcing /etc/bash_completion it completes almost everything (package names in apt... etc) :-) To make this permanent, put something like this in your .bashrc: if [ -f /etc/bash_completion]; then source /etc/bash_completion fi

Display unique values of a column
the column number is '6'

Install pip with Proxy
Installs pip packages defining a proxy

Coping files, excluding certain files
Preserve file structure when coping and exclude some file o dir patterns


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