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Slightly More Advanced Basic Bash

Let's explore some of the power that the command line gives us. Create your own small purpose-built 'programs' -- things you string together from existing programs and shell commands.

Hidden files and directories

ls
ls -alh # .EVILHACKERFILE_bwaaahahahahaaa

Input and Output redirection

echo "hi there" > logfile.log  # mistake! will overwrite each time
echo "hi again" >> logfile.log

We need dynamic stuff! Command substitution:

echo "$(/bin/date) - Checking in."

AND, OR

# AND (&&)
"hi there" && (AND IF THAT WORKS) echo "Done" >> success.log

# OR (||)
boodlehoffer || echo "no such command, dude" >> failure.log
ls -alh || echo "list failed" >> failure.log

grep

search for stuff and only print out matching lines

grep "addr" /etc/network/interfaces

Pipes -- tie together multiple commands

Got a command? Want to refine, sort, or continue doing stuff to its output? Use a pipe (or multiple pipes!)

grep "addr" /etc/network/interfaces | grep 192