Shell Learning Essays

Umask Set permission mask

General default mask is 022

Directory highest permissions 777

File maximum permissions 666

Based on mask, permissions are

777-022 = 755

666-022 = 644

1.   String test /p>

    test 

    1) detects if the variable is null  

       [-Z $var] 

       If you are empty, perform the following

       [z $var] && touch filename

2. Program exit status

   Example: Test string

     & nbsp [-Z ']

      echo $?  # 0

      [-Z "AAA"]

      echo $?  # 1

     0 is normal, 1 is abnormal  

   
   

3. Test Status

   File:
      -D directory

       x executable

      -w writable

    -S   file length is not empty

    -R   readable
    -l sign Connection
    -F   Regular file

   1) test whether the file can be executed

   [-x filename]

   Echo $?< BR>2) test is a regular file, if it is a directory, does not pass
   [-F tttt];echo $?
   

4. 
   

This article is from the "Nickylans" blog, make sure to keep this source http://378359.blog.51cto.com/368359/1908872

Shell Learning Essays