IT 244: Introduction to Linux/Unix

IT 244: Introduction to Linux/Unix
Class 22 Exercise

Use test with the -eq (equality for numbers) operator
```
test 4 -eq 5; echo $?
```
Since anything other than 0 as an exit status signals failure, this means that the equality test has failed.
Use the -eq operator with the same number on both sides
```
test 4 -eq 4; echo $?
```
Since 0 means success, this means that the expression evaluated to true.
Use test with the -ne (not equal for numbers) operator
```
test 4 -ne 5; echo $?
```
0 means true.
Use -ne again
```
test 4 -ne 4; echo $?
```
1 means false.

Use test with the -gt (greater than) operator

test 4 -gt 5  ; echo $?
test 5 -gt 4  ; echo $?

Use the -ge (greater than or equal to) operator

test 5 -ge 4 ; echo $?
test 5 -ge 5 ; echo $?

Use the -lt (less than operator)

test 4 -lt 5 ; echo $?
test 5 -lt 4 ; echo $?

Use the -le (less than or equal to) operator

test 4 -le 5 ; echo $?
test 4 -le 4 ; echo $?

Use test with the = (string equality) comparison operator

st1=FOO; st2=BAR; empty=''
test "$st1" = "$st1"; echo $?
test "$st1" = "$st2"; echo $

Use test with the != (string not equal) comparison operator

test "$st1" != "$st1"; echo $?
test "$st1" != "$st2"; echo $?

Use test with the -n (length greater than 0) string operator
```
test -n "$st1"; echo $?
test -n "$empty"; echo $?
```

Use test with the -z (length is 0) string operator

test -z "$st1"; echo $?
test -z "$empty"; echo $?

Change the permissions on arg_test.sh to make it executable
```
chmod 755 arg_test.sh
```

Test the script several times

./arg_test.sh
./arg_test.sh foo
./arg_test.sh foo bar
./arg_test.sh foo bar bletch

Test your script
```
~ghoffman/it244_test/ex22.sh
```
When the script asks if you are ready for more, hit Return or Enter.
Let me check your script