003_ File operation of Linux common commands

1. File operation
  • touch command
    • Create a file. If the file name does not exist, create it directly. If it exists, change the access time
    • touch [option] filename1 filename2...
root@ubuntu:~/Test# touch hello.c
root@ubuntu:~/Test# ls
hello.c
  • rm command: delete file or directory

    • Parameter - r recursively delete subdirectories
    • rm -rf * delete all contents in the current directory (mandatory deletion, use with caution)
  • cp and mv commands, equivalent to Windows platform copy and cut

    • cp [option] srcpath despath
    • Despath is a directory. Copy srcpath to the despath directory
    • Despath is not a directory. Create a XXX file under... / in the superior directory (... / xxx) of despath, and copy the contents of srcpath
  • cat command

    • Cat file name: display file information directly to the screen
  • more and less, display file information by screen

    • more:

      • Enter line by line
      • Space, page by page display
    • less:

      • Enter or up and down arrow keys can repeatedly view the contents of the file
  • head and tail commands

    • head view file header, default display 10 lines of content
      • head -n the number of rows that can be specified
    • tail view the end of the file, default display 10 lines of content
      • -n can specify a function
      • -f can trace the end of the file
2. Statistical information related
  • wc command: the English word is word cout, which is the content of the statistics file
    • -l) display line
    • -w word
    • -c bytes
root@ubuntu:~/Test# wc hello.c 
 8 10 91 hello.c
root@ubuntu:~/Test# wc -l hello.c 
8 hello.c
root@ubuntu:~/Test# wc -w hello.c 
10 hello.c
root@ubuntu:~/Test# wc -c hello.c 
91 hello.c
  • df displays disk space information
root@ubuntu:~# df -h 
//File system capacity used% mount points available
udev            973M     0  973M    0% /dev
tmpfs           199M  9.0M  190M    5% /run
/dev/sda1        21G  9.2G   11G   48% /
tmpfs           992M  256K  992M    1% /dev/shm
tmpfs           5.0M  4.0K  5.0M    1% /run/lock
tmpfs           992M     0  992M    0% /sys/fs/cgroup
tmpfs           199M   60K  199M    1% /run/user/1000
3. File permissions and user attributes
  • Explain the corresponding fields
root@ubuntu:~/Test# ls -l
//Total dosage 4
-rw-r--r-- 1 root root 91 10 Month 27 14:16 hello.c
  • -Represents the file type and d represents the directory file

  • rw - the permission of the user who has read and write permission

  • The group has read only permissions

  • r -- other user permissions, which are also readable only

  • We can also use octal digits to represent permission bits

    • rw - --- > 110 --- > 6 user bits
    • r -- - > 100 -- > 4 group permission bits
    • r -- - > 100 -- > 4 other permission bits
    • Finally, they are combined 0664
  • Oh, by the way, there is also a 1, which represents the count of hard links. There will be a command to demonstrate below

  • Create hard link - ln src des

root@ubuntu:~/Test# ln hello.c hello.c.hard
root@ubuntu:~/Test# ls
hello.c  hello.c.hard
root@ubuntu:~/Test# ln hello.c hello.c.hard1
root@ubuntu:~/Test# ls -l
//Total dosage 12
-rw-r--r-- 3 root root 91 10 27 14:16 hello.c
-rw-r--r-- 3 root root 91 10 27 14:16 hello.c.hard
-rw-r--r-- 3 root root 91 10 27 14:16 hello.c.hard1

At this point, the hard link count changes to 3. When our hard link count changes to 0, the file will also be deleted

  • Create a soft link -- ln -s file or directory
root@ubuntu:~/Test# ln -s hello.c hello.c.soft
root@ubuntu:~/Test# ls -l
//Total dosage 12
-rw-r--r-- 3 root root 91 10 Month 27 14:16 hello.c
-rw-r--r-- 3 root root 91 10 Month 27 14:16 hello.c.hard
-rw-r--r-- 3 root root 91 10 Month 27 14:16 hello.c.hard1
lrwxrwxrwx 1 root root  7 10 Month 27 14:43 hello.c.soft -> hello.c
  • Remove soft and hard links: unlink
4. Change document authority
  • chmod command

    • chmod [u|g|o|a] [+|-][r|w|x] filename
    • Change the file permission in numerical way, for example: chmod 0664 main.c
  • chown and chgrp change users and change groups

    • If the current user is not root, you need to use the administrator to modify the file ownership
    • chown user: Group filename | directory
    • chgrp group filename directory

Keywords: Linux Ubuntu less Windows

Added by evo4ever on Mon, 29 Jun 2020 11:43:38 +0300