brock@montreat:~/csci431/webpage/notes$ echo $SHELL
/bin/bash
brock@montreat:~/csci431/webpage/notes$ test -e /etc/passwd
brock@montreat:~/csci431/webpage/notes$ echo $?
0
brock@montreat:~/csci431/webpage/notes$ test -b /etc/passwd
brock@montreat:~/csci431/webpage/notes$ echo $?
1
brock@montreat:~/csci431/webpage/notes$ foo=5
brock@montreat:~/csci431/webpage/notes$ echo foo
foo
brock@montreat:~/csci431/webpage/notes$ echo $foo
5
brock@montreat:~/csci431/webpage/notes$ bar=7
brock@montreat:~/csci431/webpage/notes$ test -z ""
brock@montreat:~/csci431/webpage/notes$ echo $?
0
brock@montreat:~/csci431/webpage/notes$ test 5 -lt 4
brock@montreat:~/csci431/webpage/notes$ echo $?
1
brock@montreat:~/csci431/webpage/notes$ test 4 -lt 5 ; echo $?
0
brock@montreat:~/csci431/webpage/notes$ expr 5 + 6
11
brock@montreat:~/csci431/webpage/notes$ set x=5
brock@montreat:~/csci431/webpage/notes$ echo $x

brock@montreat:~/csci431/webpage/notes$ echo $(x=5)

brock@montreat:~/csci431/webpage/notes$ x="expr 5 + 6"
brock@montreat:~/csci431/webpage/notes$ echo x
x
brock@montreat:~/csci431/webpage/notes$ x=`expr 5 + 6`
brock@montreat:~/csci431/webpage/notes$ echo x
x
brock@montreat:~/csci431/webpage/notes$ echo $x
11
brock@montreat:~/csci431/webpage/notes$ x="expr 5 + 6"
brock@montreat:~/csci431/webpage/notes$ echo $x
expr 5 + 6
brock@montreat:~/csci431/webpage/notes$ a=3
brock@montreat:~/csci431/webpage/notes$ b=5
brock@montreat:~/csci431/webpage/notes$ c=17
brock@montreat:~/csci431/webpage/notes$ x=100
brock@montreat:~/csci431/webpage/notes$ expr $a
3
brock@montreat:~/csci431/webpage/notes$ expr $a*$x*$x
3*100*100
brock@montreat:~/csci431/webpage/notes$ eval $a*$x*$x
3*100*100: command not found
brock@montreat:~/csci431/webpage/notes$ expr $a * $x * $x
expr: syntax error
brock@montreat:~/csci431/webpage/notes$ expr 5 * 6
expr: syntax error
brock@montreat:~/csci431/webpage/notes$ expr 5 \* 6
30
brock@montreat:~/csci431/webpage/notes$ expr $a \* $x \* $x + $b \* $x + $c
30517
brock@montreat:~/csci431/webpage/notes$ which [
/usr/bin/[
brock@montreat:~/csci431/webpage/notes$ ls -l /usr/bin/[
-rwxr-xr-x 1 root root 51384 Jan 18  2018 '/usr/bin/['
brock@montreat:~/csci431/webpage/notes$
brock@montreat:~/csci431/webpage/notes$ which [
/usr/bin/[
brock@montreat:~/csci431/webpage/notes$ which test
/usr/bin/test
brock@montreat:~/csci431/webpage/notes$ ls -l /usr/bin/[
-rwxr-xr-x 1 root root 51384 Jan 18  2018 '/usr/bin/['
brock@montreat:~/csci431/webpage/notes$ ls -l /usr/bin/test
-rwxr-xr-x 1 root root 47288 Jan 18  2018 /usr/bin/test
brock@montreat:~/csci431/webpage/notes$ which let
brock@montreat:~/csci431/webpage/notes$ let x=5+11
brock@montreat:~/csci431/webpage/notes$ echo $x
16
brock@montreat:~/csci431/webpage/notes$ echo $x
17
brock@montreat:~/csci431/webpage/notes$ $(( 4 + 5 ))
9: command not found
brock@montreat:~/csci431/webpage/notes$ $(( 235 + 431 ))
666: command not found
brock@montreat:~/csci431/webpage/notes$ x=$(( 235 + 431 ))
brock@montreat:~/csci431/webpage/notes$ echo $x
666
brock@montreat:~/csci431/webpage/notes$