Ubuntu Unleashed 2019 Edition: Covering 18.04, 18.10, 19.04

is, comparing values using characters representing NOT, AND, and OR:

!—Negates   a   logical expression

-a—Logically    ANDs    two logical expressions

-o—Logically    ORs two logical expressions

This example named logic uses the file and directory mentioned in the
previous compare3 example:

Click here to view code image
#!/bin/sh
if [ -x file1 -a -x dir1 ]; then
echo file1 and dir1 are executable
else
echo at least one of file1 or dir1 are not executable
fi

if  [   -w  file1   -o  -w  dir1    ];  then

            echo    file1   or  dir1    are writable

else

            echo    neither file1   or  dir1    are executable

fi

if  [   !   -w  file1   ];  then

            echo    file1   is  not writable

else

            echo    file1   is  writable

fi

If you execute logic, it yields the following result:

Click here to view code image
file1 and dir1 are executable
file1 or dir1 are writable
file1 is not writable

Comparing Expressions with tcsh

As stated earlier, the method for comparing expressions in tcsh is different
from the method used under pdksh and bash. The comparison of
expression demonstrated in this section uses the syntax necessary for the
tcsh shell environment.

String Comparison

You can use the following operators to compare two string expressions: