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

When things work on one server but are broken on another the following lets you compare all the related libraries:

export MYLIST=`ldd amule | awk ' { print $3; }'`; for a in $MYLIST; do cksum $a; done

Compare this list with the one between the machines and you can isolate differences quickly.

Answer 2

I find commandlinefu.com to be an excellent resource for various shell scripting recipes.

Examples

Common

# Run the last command as root
sudo !!

# Rapidly invoke an editor to write a long, complex, or tricky command
ctrl-x ctrl-e

# Execute a command at a given time
echo "ls -l" | at midnight

Esoteric

# output your microphone to a remote computer's speaker
dd if=/dev/dsp | ssh -c arcfour -C username@host dd of=/dev/dsp

Answer 3

Your shell is the most powerful tool you have available

1. being able to write simple loops etc
2. understanding file globbing (e.g. *.java etc.)
3. being able to put together commands via pipes, subshells. redirection etc.

Having that level of shell knowledge allows you to do enormous amounts on the command line, without having to record info via temporary text files, copy/paste etc., and to leverage off the huge number of utility programs that permit slicing/dicing of data.

Unix Power Tools will show you so much of this. Every time I open my copy I find something new.

Answer 4

Start all WebService(s)

     find -iname '*weservice*'|xargs -I {} service {} restart

Search a local class in java subdirectory

     find -iname '*.java'|xargs grep 'class Pool'  

Find all items from file recursivly in subdirectories of current path:

     cat searches.txt| xargs -I {} -d, -n 1 grep  -r {} 

P.S searches.txt: first,second,third, ... ,million

Answer 5

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

Answer 6

Finding PIDs without the grep itself showing up

export CUPSPID=`ps -ef | grep cups | grep -v grep | awk '{print $2;}'`