One-liners

one_liners

Replace all instances of old_string with new_string recursively within the current directory and its sub-directories:

grep -rl old_string * | xargs sed -i '' 's/old_string/new_string/g'


Sum all numbers in your file (assuming that the numbers are the first column, one per line):

awk '{s+=$1} END {print s}' $filename  
  
  
List all ports a process is using:

lsof -a -pPID -i4 (or -i6)  
  
  
List what process is using a port:  
  
lsof -i :PORT