Ubuntu Unleashed 2019 Edition: Covering 18.04, 18.10, 19.04

If you execute the file compare3, you get the following results:

Click here to view code image
dir1 is a directory
file1 is a regular file
file1 has read permission
file1 does not have write permission
dir1 has execute permission
file1 has greater than zero length

Logical Operators

You use logical operators with conditional statements. You use the following
operators to negate a logical expression or to perform logical ANDs and ORs:

!—Negates   a   logical expression

&&—Logically    ANDs    two logical expressions

||—Logically    ORs two logical expressions

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

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#!/bin/tcsh
if ( -x file1 && -x dir1 ) then
echo file1 and dir1 are executable
else
echo at least one of file1 or dir1 are not executable
endif

if  (   -w  file1   ||  -w  dir1    )   then

            echo    file1   or  dir1    are writable

else

            echo    neither file1   or  dir1    are executable

endif

if  (   !   -w  file1   )   then

            echo    file1   is  not writable

else

            echo    file1   is  writable

endif

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