UNIX / LINUX quick reference

I have compiled the Unix/Linux code snippets below as a quick reference covering the "how to" on various topics. Please feel free to leave a comment with your own "Unix command line gems".

How to:

# list top memory processes on a Linux machine:
ps aux | awk '{print $4"\t"$11}' | sort | uniq -c | awk '{print $2" "$1" "$3}' | sort -nr

# show how many CPUs on a Linux machine:
cat /proc/cpuinfo

# create a symbolic link:
ln -s originalPath newLinkPath
e.g. ln -s /usr/local/apache/logs /tmp/apachelogs

# list largest files in Linux (good for file system cleanup):
find / -type f -size +20000k -exec ls -lh {} \; 2> /dev/null | awk '{ print $NF ": " $5 }' | sort -nk 2,2

# list largest directories in Linux:
du -h / | grep ^[0-9.]*G | sort -g
du -h / | grep ^[0-9.]*M | sort -g | more
find / -type d -size +1G

# split big text files into smaller and more manageable files
split --lines=100000 --suffix-length=3 application.log application.log.a

# redirect Linux output:
ls 1> out.log 2> err.log

# do global string replaces in the VI editor:
:%s/old_string/new_string/g

# set executable tag in shell script files recursivelly:
find . -name "*.sh" -exec chmod +x+x+x {} \;

# delete bak and log files recursivelly:
find . -name "*.bak" -exec rm {} \;
find . -name "*.log" -exec rm {} \;

# recursively determine how much space a directory is taking:
df -h : shows how much space we have on each partition
du -sh * : show how much space the current directory is taking
du -h | grep -v '/' | awk '{print $1}' : does the same without iterating thru the subdirs

# find files that contain a given text string
grep -lir "/data/platform" *

# find files that contain a given text string recursively
find . * -exec grep -li "/data" {} \;
find . * -exec grep -li "/data" {} \; > files.txt

# poll the number of files in a folder every 3 seconds
ksh
while true
do
ls *.retry.xml | wc -l
sleep 3
done

# archive a folder and sub-directories in tar/gz
tar -zcvf archive.tgz directory
e.g. tar -zcvf apacheLogs.tgz /usr/local/apache/logs

# extract a tar/gz archive
tar -xvf archive.tgz directory
e.g. tar -xvf  apacheLogs.tgz .

These are just some of the ones I use the most. You can also find many more at the Unix Toolbox here.