Shell determines whether the input variable or parameter is empty

Judging variables

Read-p "Input a word:" Word

If [!-n "$word"] ; then

echo "You had not input a word!"

Else

echo "The word you are input is $word"

Fi

Judging input parameters

#!/bin/bash

if [!-n "$"]; then

echo "You had not input a word!"

Else

echo "The word you are input is $"

Fi

The following is not verified, transferred from http://blog.csdn.net/lllxy/article/details/3255554

2. Judging directly by variables

The results are as follows: Is NULL

1. #!/bin/sh

2. para1=

3. if

   [

   !

   $para 1

   ];

   Then

4. Echo

   "Is NULL"

5. Else

6. Echo

   "Not NULL"

7. Fi

3. Use test to determine

      is that DMin is not set!  

1. #!/bin/sh

2. dmin=

3. if

   Test

   -Z

   "$dmin"

4. Then

5. Echo

   "DMin is not set!"

6. Else

7. Echo

   "DMin is set!"

8. Fi

4. Use "" to determine the

1. #!/BIN/SH 

2. dmin=

3. if  

   [ 

   "$ DMin "  

   = 

    

   ]

4. Then

5.  

    

   echo 

   "dmin is not set!"

6. else  

    

7.  

    

   echo 

   "dmin is set !"

8. Fi

Shell determines whether the input variable or parameter is empty