Linx link, first level directory, redirection, CP and MV

Catalog

1. Hard links and soft links

2. First level directory

3.I/O flow 、 Redirect

4. Creation and deletion of files and directories

5. Copy 、 Move

---

 

 

1. Hard links and soft links

Symbolic links are also called soft links

• And the original file is not a file for example Windows Shortcut to , If the original file is deleted , all
• The symbolic links pointing to it are also destroyed .
• Soft links have their own node, yes linux A kind of special document , As a document , Its data is the path of the file to which it is connected . Symbolic links can span file systems , You can also create a directory .
• Format ：ln -s  Source file   Target file

Hard links

• Only files in the same file system can be referenced . It refers to the physical index of the file in the file system （ Also known as inode）.
• When the original file is moved or deleted , Hard links will not be broken , Because it refers to the physical data of the file, not the location of the file in the component structure .
• Create format ： ln The original document Target file

create a file file1 And create soft links for it soft_file1、 And hard links hard_file1

[[email protected] home]# touch file1
[[email protected] home]# ln -s file soft_file1
[[email protected] home]# ln file hard_file1
[[email protected] home]# ls -li
total 5
27446429 drwxr-xr-x.  2 root  root     6 Jul 14 10:46 data
27446447 -rw-r--r--.  2 root  root     0 Jul 14 18:15 file1
27446447 -rw-r--r--.  2 root  root     0 Jul 14 18:15 hard_file1
18732229 drwx------. 15 rhcsa rhcsa 4096 Jul 12 17:45 rhcsa
27446463 lrwxrwxrwx.  1 root  root     5 Jul 14 18:19 soft_file1 -> file1
 1875985 drwxr-xr-x.  2 root  root     6 Jul 14 10:46 sub_data

Delete file1 Then check the contents of each document

[[email protected] home]# echo "123456" > file1
[[email protected] home]# echo "999999" >> hard_file1
[[email protected] home]# cat file1
123456
[[email protected] home]# cat soft_file1
123456
[[email protected] home]# cat hard_file1
123456
999999

[[email protected] home]# rm file1
rm: remove regular file 'file1'? y
[[email protected] home]# cat file1
cat: file1: No such file or directory
[[email protected] home]# cat soft_file1
cat: soft_file1: No such file or directory
[[email protected] home]# cat hard_file1
999999

2. First level directory

• /bin/   Store system commands , Ordinary users and root Can be executed . Put it in /bin The command under can also be executed in single user mode
• /boot/   System boot directory , Save files related to system startup , Such as kernel files and boot loader （grub） Documents, etc.
• /dev/   Device file storage location
• /etc/   Where to save the configuration file . The default installation mode is adopted in the system （rpm install ） The service configuration files of are all saved in this directory
• /home/   Home directory for ordinary users （ Also known as home directory ）
• /lib/   The function library of the system call is saved in
• /lib64    Deposit 64 Bit file
• /media/     Mount Directory . The system is recommended to mount media devices , Such as floppy disk and CD
• /mnt/     Mount Directory . The system suggests that this directory be used to mount additional devices , Such as U disc 、 Partition of mobile hard disk and other operating systems
• /opt/     Storage location of software installed by a third party . This directory is where other software is placed and installed , Manually installed source package software can be installed into this directory
• /proc/   Virtual file system . The data in this directory is stored in memory . It mainly stores the kernel of the system 、 process 、 External device status and network status etc
• /root/   root The home directory . The home directory of ordinary users is in /home/ Next ,root The home directory is directly in “/” Next
• /sbin/   Save commands related to system environment settings , Only root You can use these commands to set the system environment , There are also commands that allow ordinary users to view
• /srv/     Service data directory . After some system services are started , You can save the required data in this directory
• /sys/     Virtual file system . and /proc/ The catalog is similar to , The data in this directory is stored in memory , It mainly stores kernel related information
• /tmp/     Temporary directory . The directory where the system stores temporary files , Under the directory , All users can access and write
• /tmp    This directory is where some temporary files are stored .
• /usr   Its full name is Unix Software Resource, This directory is used to store system software resources
• /var   Used to store dynamic data , For example, caching 、 Log files 、 Files generated during software operation, etc

3.I/O flow 、 Redirect

Field	describe	File descriptor
stdin	Standard input stream	0
stdout	Standard output stream	1
stderr	Standard error output stream	2

Redirection operator

• Redirection operators can redirect command input and output data streams from the default device to other locations . The redirection operator itself is not a command , It is a special symbol attached to the command that can change the input and output objects of the command .
• Output redirection operator ： >（ Cover ） 、 >>（ Additional ）
• Enter the redirection operator ： < 、 <<（ end ）

Redirect standard output and standard error output to the same file  

[[email protected] ~]# date &> file
[[email protected] ~]# cat file
Thu Jul 14 19:54:09 CST 2022
[[email protected] ~]# data &> file
[[email protected] ~]# cat file
bash: data: command not found...


[[email protected] ~]# date >& file
[[email protected] ~]# cat file
Thu Jul 14 19:55:16 CST 2022
[[email protected] ~]# data >& file
[[email protected] ~]# cat file
bash: data: command not found...

[[email protected] ~]# date 1> file 2>file
[[email protected] ~]# cat file
Thu Jul 14 19:56:19 CST 2022
[[email protected] ~]# data 1> file 2>file
[[email protected] ~]# cat file
bash: data: command not found...

take 1 Redirect to 2

[[email protected] ~]# date 2> file 1>&2
[[email protected] ~]# cat file
Thu Jul 14 20:00:36 CST 2022
[[email protected] ~]# data 2> file 1>&2
[[email protected] ~]# cat file
bash: data: command not found...

[[email protected] ~]# date 1>& file 
[[email protected] ~]# cat file
Thu Jul 14 20:02:16 CST 2022
[[email protected] ~]# data 1>& file 
[[email protected] ~]# cat file
bash: data: command not found...

take 2 Redirect to 1

[[email protected] ~]# data 1>file 2>&1
[[email protected] ~]# cat file
bash: data: command not found...
[[email protected] ~]# date 1>file 2>&1
[[email protected] ~]# cat file
Thu Jul 14 20:04:19 CST 2022

Redirect files to 0

[[email protected] ~]# ecoh "hello world" >data
[[email protected] ~]# sort <data
hello world

[[email protected] ~]# cat <<EOF
> 123
> 456
> 789
> hello world!
> EOF

[[email protected] ~]# cat > data <<EOF
> 111
> 222
> 777
> EOF
[[email protected] ~]# cat data
111
222
777

4. Creation and deletion of files and directories

Catalog ：

Create directory (make directory)

• The grammar is ： mkdir [-p] [/ route /] Directory name
• -p You can quickly create each directory specified in the directory structure , Existing directories will not be overwritten
• -v Displays the detailed process of creating a directory

Statistics of space occupation of directory and file ——du command

• function ： View the amount of disk space occupied by subdirectories at all levels in a directory .
• Command format ： du [ Options ] [ Directory name ]

-a  Include all files when calculating disk space usage , It's not just catalogues .
-s  Only count the total space occupied by each file , Instead of counting every subdirectory 、 File size .
-h   With K,M,G Displays disk usage in units , To improve the readability of information .

[[email protected] data]# mkdir -p /home/data/cont1
[[email protected] cont1]# pwd
/home/data/cont1
[[email protected] cont1]# echo "hello world!">>cont1
[[email protected] cont1]# du -h cont1
4.0K	cont1
[[email protected] cont1]# mkdir -p cont2/cont3
[[email protected] data]# ls -R 
.:
cont1

./cont1:
cont2

./cont1/cont2:
cont3

Delete directory files

Grammar format ： rm -r [-f] Directory file name

[[email protected] data]# rm -r cont1/cont2/cont3
rm: remove directory 'cont1/cont2/cont3'? y
 Only deleted cont3

[[email protected] data]# rm -r cont1
rm: descend into directory 'cont1'? y
rm: descend into directory 'cont1/cont2'? y
rm: remove directory 'cont1/cont2/cont3'? y
rm: remove directory 'cont1/cont2'? y
rm: remove directory 'cont1'? y
 Deleted cont1、2、3

file

Create a normal file ： touch [OPTION]... FILE...

touch In two ways ：

1. If the file already exists , Three times when the file will be updated , stat You can view the details of the file
2. If the file doesn't exist , It means to create a file

Create multiple normal files ：

• Method 1： touch  file name 1 file name 2 file name 3
• Method 2： touch  { file name 1, file name 2, file name 3}

Delete normal files ： rm [-f] file name

[[email protected] data]# touch file11 file22 file33

[[email protected] data]# ls -l
total 0
-rw-r--r--. 1 root root 0 Jul 14 21:35 file11
-rw-r--r--. 1 root root 0 Jul 14 21:35 file22
-rw-r--r--. 1 root root 0 Jul 14 21:35 file33

[[email protected] data]# stat file33
  File: file33
  Size: 0         	Blocks: 0          IO Block: 4096   regular empty file
Device: fd00h/64768d	Inode: 27446851    Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Context: unconfined_u:object_r:user_home_t:s0
Access: 2022-07-14 21:25:35.549327296 +0800
Modify: 2022-07-14 21:25:35.549327296 +0800
Change: 2022-07-14 21:25:35.549327296 +0800
 Birth: 2022-07-14 21:25:35.549327296 +0800

[[email protected] data]# touch file33
[[email protected] data]# stat file33
  File: file33
  Size: 0         	Blocks: 0          IO Block: 4096   regular empty file
Device: fd00h/64768d	Inode: 27446851    Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Context: unconfined_u:object_r:user_home_t:s0
Access: 2022-07-14 21:32:28.028280247 +0800
Modify: 2022-07-14 21:32:28.028280247 +0800
Change: 2022-07-14 21:32:28.028280247 +0800
 Birth: 2022-07-14 21:25:35.549327296 +0800

[[email protected] data]# rm file11
rm: remove regular file 'file11'? y
[[email protected] data]# rm file22
rm: remove regular empty file 'file22'? y
[[email protected] data]# rm file33
rm: remove regular empty file 'file33'? y
[[email protected] data]# ls -l
total 0

5. Copy 、 Move

1、 Copy files or directories

Format ： cp [ Options ] Source file Target file

• -a  Usually used when copying directories , Keep all its contents . It retains links 、 File attribute , And copy directories recursively
• -d   Keep links when copying
• -f    Force copying of files or directories , Whether the target directory or file exists or not
• -i    You will be prompted to confirm before overwriting the target file . answer y When the target file will be overwritten , It's an interactive copy
• -p  -preserve, Keep its properties , In addition to copying the contents of the source file , It will also copy its modification time and access rights to the new file
• -r/g    Recursive replication , Copy all the files in the specified directory together with the sub files

Copy files to the current directory rename ../ Represents the current directory  

[[email protected] data]# cp file11 ./file11-1
[[email protected] data]# ls -l
total 16
-rw-r--r--. 1 root root 13 Jul 14 21:51 file11
-rw-r--r--. 1 root root 13 Jul 14 21:56 file11-1

Copy the file to the directory without changing the file properties

[[email protected] data]# cp -p file22 /home/data/cont2/

Copy to the specified directory cont1

[[email protected] data]# cp file11 /home/data/cont1/

[[email protected] data]# ls -la cont1
total 4
-rw-r--r--. 1 root root  13 Jul 14 22:04 file11

  Put the table of contents cont3 And the files under it are copied to cont4, If you only move the directory, remove cont3 hinder /*

[[email protected] data]# cp -r /home/data/cont3/* /home/data/cont4/
cp: overwrite '/home/data/cont4/cont3'? y
[[email protected] data]# ls -l cont4
total 4
-rw-r--r--. 1 root root 45 Jul 14 22:32 cont3
drwxr-xr-x. 2 root root  6 Jul 14 22:32 count3.3
drwxr-xr-x. 2 root root  6 Jul 14 22:22 count4.4

  Copy, paste and rename under the current directory

[[email protected] data]# echo "hello world!" >>file11
[[email protected] data]# cp file11 file22
[[email protected] data]# cat file44
hello world!

Move files or directories

• Format ： mv [ Options ] Source file name Target file name
• mv The command is used to cut or rename files
• The cut operation is different from the copy operation , Because it will delete the source file , Keep only the cut file . If you cut a file in the same directory and paste it into the current directory , In fact, the essence is to rename the file .

[[email protected] cont4]# mv /home/data/cont3 /home/data/cont5
[[email protected] cont4]# ls -l cont5
[[email protected] data]# ls -l cont5
total 0
drwxr-xr-x. 3 root root 35 Jul 14 22:27 cont3