how to get help from linux

1.man

• z,w scroll a window
• d,u scroll half window
• g,^g from begin to end

2.--help

3.-h

ls

access time :atime
    Access time shows the last time the data from a file was accessed – read by one of the Unix processes directly or through commands and scripts

change time :ctime
    ctime also changes when you change file's ownership or access permissions. It will also naturally highlight the last time file had its contents updated.

modify time :mtime
    Last modification time shows time of the  last change to file's contents. It does not change with owner or permission changes, and is therefore used for tracking the actual changes to data of the file itself.

ls -l
    show mtime
ls -lu 
    show atime
ls -lc
    show ctime

stat filename
    show atime,ctime,mtime

-l show 7 column information

• first line is totoal size (default size kb)

• first column:file type and permission

  1. 10 letter
     • first letter is file type(-,d,l,P,s)
     • 9 leeter is show permission
       • 1-3 letter means owner
       • 4-6 means same group user
       • 7-9 means other user
  2. 文件硬链接数
     • ln test test2
     • ln -s test test_s1
  3. owner
  4. group
  5. size(byte)
  6. last modify time
  7. filename