Most powerful examples of Unix commands or scripts every programmer should know

Question

There are many things that all programmers should know, but I am particularly interested in the Unix/Linux commands that we should all know. For accomplishing tasks that we may

Answer 1

The tr command is the most under-appreciated command in Unix:

#Convert all input to upper case
ls | tr a-z A-Z

#take the output and put into a single line 
ls | tr  "\n" " "

#get rid of all numbers
ls -lt | tr -d 0-9