I count shell scripting and SQL as two skills that will never go out of date. Both have been around since the early 1970s, and I don’t see either being replaced anytime soon. Spend your time learning these technologies, and you will have an excellent return on investment.

Here are some of what I consider to be the best resources for learning the magical spells you can cast at the command prompt.

UNIX for the Beginning Mage - Joe Topjian

UFBM is focused on teaching you how to effectively navigate the UNIX Shell.

Up and Running with Bash Scripting - Scott Simpson

This course on Linda.com

Linda.com access is free to Boston Public Libray card holders.

UNIX for Mac OS X Users - Kevin Skoglund

Another course on Linda.com

Other Stuff

Syntax Highlighting in nano

$ brew tap homebrew/dupes
$ brew install nano

Add include /usr/local/share/nano/*.nanorc to ~/.nanorc.

Update Bash

$ brew install bash

Bash Homepage

Basic Commands

pwd
ls
ls -l folder_name
mkdir folder_name
rmdir folder_name
clear
cd folder_name
cp filename new_filename
rm filename
cat filename
more filename
head filename
tail filename

Expansions

cd ~
cd ~-
touch {file_one,file_two,file_three,file_four}
echo {01..100}

Pipes and Redirection

| - pipe the output of one command to the input of another > - redirect output 1 - stdout 2 - stderr & - stdout & stderr

ls | more
cp -v * ../otherfolder 1>../success.txt 2>../error.txt
cp -v * ../otherfolder &>../log.txt
grep -i break-in auth.log | awk {'print $12'}
sed
ping -c 1 example.com | grep 'bytes from' | cut -d = -f 4

Create Bash Scripts

#!/bin/bash
# my.sh
ls

chmod +x my.sh

Variables

#!/bin/bash
greeting_one=Hello
greeting_two="Good Morning"
age=35

echo $greeting_one, $greeting_two, $age

declare -i thing_one=123  # thing_one is an integer
declare -r thing_two=456  # thing_two is read-only
declare -l datatype="String"  # to lowercase
declare -l datatype="String"  # to uppercase

echo $HOME
echo $PWD
echo $MACHTYPE
echo $HOSTNAME
echo $BASH_VERSION
echo $SECONDS
echo $0  # name of the script

Bash Variables

Command Substitution

#!/bin/bash
current_directory=$(pwd)
echo $current_directory

response_time=$(ping -c 1 example.com | grep 'bytes from' | cut -d = -f 4)
echo "The response time was $response_time"

Strings

a="hello"
b="world"

c=$a$b      # concatenation
echo ${#a}  # length
d=${c:3}    # substring
d=${c:3:4}  # substring

# find/replace
fruit="apple banana banana cherry"
echo ${fruit/banana/durian}
echo ${fruit//banana/durian}

echo ${fruit/#apple/durian}
echo ${fruit/%cherry/durian}
echo ${fruit/c*/durian}

Math in Bash

Wrap expressions in double parenthesis: (( 5 + 3 )) Variable assignment: result=$(( 5 + 3 ))

Operation	Operator
Exponentiation	$x ** $y
Multiplication	$x * $y
Division	$x / $y
Modulo	$x % $y
Addition	$x + $y
Subtraction	$x - $y
Increment	$x++
Decrement	$x–

Warning: Integer division. Use bc

#!/bin/bash
$one_third=$(echo 1/3 | bc -l)

Comparison Operations for Strings

Use double square brackets when making comparisons: [[ $x < $y ]]

1 is FALSE
0 is TRUE

Operation	Operator
Less than	$x < $y
Greater than	$x > $y
Less than or equal to	$x <= $y
Greater than or equal to	$x >= $y
Equal	$x == $y
Not Equal	$x != $y
Is null?	-z $x
Is not null?	-n $x

[[ "zebra" == "zebra" ]]
echo $?  # return value

Comparison Operations for Numbers

Operation	Operator
Less than	$x -lt $y
Greater than	$x -gt $y
Less than or equal to	$x -le $y
Greater than or equal to	$x -gt $y
Equal	$x -eq $y
Not Equal	$x -ne $y

Logic Operations

Operation	Operator
Logical AND	$x && $y
Logical OR	$x	$y
Logical NOT	! $a

Conditional Statements

if [[ -a ~/.vars ]]; then
  source ~/.vars
fi

Looping and Arrays

RubyVersions=( '2.3.1' '2.2.5' '2.0.0-p648' );
for version in "${RubyVersions[@]}"; do
  ruby-install ruby $version
done

Functions

sms() {
  number=$1
  shift
  curl -X POST http://textbelt.com/text -d number=$number -d "message=$*"
}