Shell Note 7

2. The result of the test is 0 or not 0, 0 is true, and not 0 means false.

4. Test command

   Typically used with statements such as if, while, until, and so on.

   #test An expression

   #test [expression]//[trailing space,] preceded by a space

5. File properties Test Expression

   
   

   An expression	Description
   -B File	True if the file exists and is a block device (block speicial)
   -C file	True if file exists and is a character device (Character special)
   -R File	True if file exists and is read-only
   -W File	True if file exists and can be written to
   -X File	True if file exists and can be executed
   -S file	The value is true if the file exists and is longer than 0
   -D File	If file is a directory, the value is True
   -F File	If the file is a normal file, the value is True
   -E File	If the file exists, the value is True

7. Test example

   
   

9.   1 #! /bin/bash  2  #filename: Filee   3 echo  "Please enter the file name:"   4 read  filename  5 if test -e  $FILENAME  ; then  6 ls -l   $FILENAME   7 else  8 touch  $FILENAME   9 fi 

11. Test values

    
    

    Options	Description
    N1-eq N2	N1 equals N2, then true
    N1-ne N2	N1 is not equal to N2, it is true
    N1-GT N2	N1 is greater than N2, it is true
    N1-lt N2	N1 is less than N2, it is true
    N1-ge N2	True if N1 is greater than or equal to N2
    N1-le N2	N1 is less than or equal to N2, true

13. Test example

15.   1 #! /bin/bash  2  #filename: Filee   3 echo  "Please enter the first number:"   4 read  n1  5 echo  "Please enter the second number:"   6 read  N2  7 if test  $N 1 -eq  $N 2 ; then  8 echo   "N1 == n2"   9 else 10 echo  "N1 != n2"  11 fi 

17. Test string

    
    

    Options	Description
    -Z S1	If the length of the string S1 is 0, the value is True
    -N S1	If the length of the string S1 is not 0, the value is True
    S1=s2	If the string S1 is equal to the string s2, the value is True
    S1!=s2	The value is true if the string S1 is not equal to the string s2
    S1	If the string S1 is not an empty string, the value is True

19. Test example

    
    

21.   1 #! /bin/bash  2  #filename: Filee   3 echo  "please enter the first string:"   4 read  s1  5 echo  "please enter the second string:"   6 read  S2  7 if test  $S 1 =  $S 2 ; then  8 echo  "S1 == s2"   9 else 10 echo  "S1 != s2"  11 fi 

23. Test logical operators

    
    

    logical operators	Description
    -A	Binary "and" operators
    -O	Binary "or" operator
    !	Unary "non" operator

25. Test example

    
    

27. 1 #!   /bin/bash 2 #filename: Filee 3 echo "Please enter the first string:" 4 read S1 5 echo "Please enter the second string:" 6 Read S2 7 if test $S 1 = $S 2-o $S 1 = "abc"; Then 8 echo "S1 = = S2" 9 Else ten echo "S1! = S2" one fi

Shell Note 7