% Modulus
/ Division
34 % 5 = 4
34 / 5 = 6
Modulus is the remainder.
echo
‘   ‘
$(    ) 
$((   ))
echo $(($RANDOM%100))        values 0-99
echo $(($RANDOM%100)+1))   values 1-100

#!/bin/bash
choice=$((($RANDOM%100)+1))
guess=0
while [ ”$guess” -lt 6 ];do
     echo -n “Guess a number:”
   read number
     if [ “$number” -eq “$choice” ]; then
     echo “You have correct now”
exit 0
elif [ “$number” -lt “$choice” ]; then
     echo “Higher”
   else
     echo “Lower”
fi
     let guess=$guess+1
done
exit 0

 cat data | grep ‘2’ | wc -l
 bc = binary calculator
 obase=16
 quit
 answer=’echo “2+2” | bc’
 echo $answer

#!/bin/bash
total=0
evens=0
for number in `cat data`; do
        evenchk=`echo "$number%2"|bc`
        if [ "$evenchk" -eq 0 ]; then
                let evens=$evens+1
fi
let total=$total+1
done
echo "Out of $total numbers, there are $evens even numbers."
exit 0

1. calculate project points
2. calculate opus points
3. calculate attendance
4. calculate project % -36%
5. calculate opus % -36%
6. calculate attendance % -28%
7. calculate current grade

<codebash> echo “6/7” | bc -l echo “(6/7)*100” | bc -l go to man bc* echo “(6/7)*100” | bc -l | cut -d`.` -f1 echo “$(echo ”(6/7)*100“ | bc -l | cut -c1-5)%” </code>

    attendance - username
    status unix | grep mgleaso7

   Only one “Enter” at the end.
   status unix | grep mgleaso7 | tr -s ' ' '\n'
   ^ new line
   $ end of a line
   grep -v ‘^$”

   missed=$(status unix | grep mgleaso7 | tr -s ' ' '\n' | grep X | wc -l)

? - match any single char
[  ] - character class. match any one of the enclosed characters.
*- match 0 or more of anything inverted character class

 . - match any single character
 * - 0 or more of the previous char class
 [^ ] - do not match one of the enclosed
 \< - match start of word
 \> - match end of word
 ^ - match start of line
 $ - match end of line

 | or
 (   ) grouping → \(  \)
 + - match one or more of the previous.
 

<codebash> cat words | grep '^[a-z][a-z][a-z][a-z]*$' | wc -l

cat words | grep '^.*[aeiouy].*[aeiouy].*[aeoiouy].*$' |wc -l

ccat words | egrep '(ed)$|(ing)$' | wc -l </code>

 egrep = grep + moar
 fgrep = fast grep, no regex

<codebash>

status unix | grep ‘opus’ | grep ‘week[02468]’

		        egrep ‘week([02468] | [0-9] [02468] )’

1 : opus : week2entry

getent passwd | grep '^[mg]' | sed 's/^\([a-z][a-z0-9]*\):x:\([0-9][0-9][0-9][0-9]\):5000:\(.*\):\/home.*$/\3 is user \1 with userid \2 /g' </code>

*/4 /usr/bin/who where is status

at commands

at - executes command at specified time

atrm - deletes job by job number

at 16:16 - sets command at 4:16 Linux time

ls > out - command that will run at 4:16

atq - shows the list of commands that you set to run

crontab -e - lets you choose an editor to create a repeating command

*/4 * * * * /usr/bin/who - runs that command every 4 minutes of every hour, day, week, month

After a successful crontab command it should say: crontab: installing new crontab

last - shows when a user logged in

last | grep $USER | wc -l - shows how many times you logged in

last | grep $USER| grep Oct | wc -l - shows how many times you logged in October