###### find dangling symlinks
	  find . -type l | while read f; do if [ ! -e "$f" ]; then ls -l "$f";fi;done

### last changed config files
	  find /etc -cmin -60

### files with nouser , nogroup under /bin, /sbin, /usr/bin, /usr/sbin, /usr/local/bin, /usr/local/sbin
	find {,/usr{,/local}}/{,s}bin -nouser
	find {,/usr{,/local}}/{,s}bin -nogroup

### packages installed except from our package management system
	find /usr/bin | xargs rpm -q --whatprovides | grep "not owned"

### in-place replacement at file
	perl -i -p -e "s/value/new_value/g" file

### find files owned by root and has sticky bit
	find / -perm /1000 -user root -ls

### find files owned by root and has sgid bit
	find / -perm /2000 -user root -ls

### find files owned by root and has suid bit
	find / -perm /4000 -user root -ls

### analyze inode usages inside an fs
	find . -xdev -type f | cut -d "/" -f 2 | sort | uniq -c | sort -rn | more

### colomn merging in command line
	# echo 1 > a
	# echo 3 >> a
	# echo 2 > b
	# echo 4 >> b
	# paste a b > c
	# cat c
	1       2
	3       4
	# cat c | tr '\t' ' '
	1 2
	3 4
	# 

### find which process created short-lived files
	# cd /folder
	# while true
	> do
	> ls -lrt | tail -1 | awk '{print $NF}' |xargs lsof
	> sleep 1
	> done
	COMMAND      PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
	java    15204468  was  465u  VREG   10,7  2097152  115 com.ab.platform.branchdata.BranchDataService.getApprovalsData.data

### calculate sum with awk
	# cat file | awk '{sum+=$1} END {print sum}'

### calculate average with awk
	# cat file | awk '{ sum += $1; n++ } END { if (n > 0) print sum / n; }'