Ask for help about shell commands in Linux.

Linux Shell common Shell commands

A, file and directory operation command

1, ls command

Function: Display information of files and directories.

Ls displays the current directory file list by default.

Ls -a displays all files, including hidden files.

Ls -l displays file properties, including size, date, symbolic link, whether it can be read or written, and whether it can be executed.

Ls -lh displays the file size and prints the file size in an easy-to-understand format (for example, 1K 234M2G).

Ls -lt displays files, sorted by modification time.

2.cd command

Function: Rename Directory

Cd dir switches to the dir directory in the current directory.

CD/ switch to the root directory

Cadmium .. Switch to the previous directory.

Cadmium .../... Switch to the superior secondary directory.

Cd ~ Switch to the user directory, such as root, and then switch to /root.

The difference between root directory and home directory:

The root directory is the first-level file structure of the system, and the home directory is only the directory controlled by non-root users. Equivalent to windows My Documents, non-root users can only control files in the home directory, but not other files in the root directory.

The root directory is the top-level directory of the device, which is marked with/

The home directory is the directory where each user logs into the system. Usually under /home, the user name is the directory, which can be represented by ~.

CD/ input root directory

Cd ~/ enter the home directory

Of course, you can also use /home/someone to enter someone's home directory.

3.cp command

Function: Copy files

Cp source target copies the file source as the target.

Cp /root /source。 Copy the file source under /root to the current directory.

For example: cp/home/open _ 038 _ dev/external _ files/test/test.sh.

CP–avsour _ dir target _ dir copies the entire directory, and the two directories are exactly the same.

4.rm command

Function: Delete files or directories.

Rm file deletes a file.

Rm -f file was deleted without prompting. Can be used with the r parameter.

Rm -rf dir deletes the entire directory named dir in the current directory.

5.mv command

Function: Move the file or rename it. There is no rename command under uinx. If you want to rename it, you can use this command.

Mv source target renames the file source to the target.

Command parameters:

-b: If you need to overwrite the file, please back it up before overwriting it.

-f: Forcing means directly overwriting the target file without asking if it already exists;

-i: If the target file already exists, you will be asked whether to overwrite it!

-u: If the target file already exists and the source file is relatively new, it will be updated.

-t:-target-directory = directory moves all source parameters to the directory, which is the target directory of the specified mv. This option is suitable for moving multiple source files to a directory, with the target directory first and the source files last.

Example 1: Rename file

Command:

Mv test. log test 1.txt

Example 2: Moving files

Command:

mv test 1.txt test3

Move the files log 1.txt, log2.txt and log3.txt to the directory test3.

mv log 1 . txt log 2 . txt log 3 . txt test3

Change the file log1.txtlog2.txtlog3.txt to the directory /opt/soft/test/test4.

mv-t/opt/soft/test/test 4/log 1 . txt log 2 . txt log 3 . txt

Move all files in the current folder to the previous directory.

mv *../

6. Differences

Function: Compare file contents

Diff dir 1 dir2 compares whether the file lists in directory 1 and directory 2 are the same, but does not compare the actual contents of the files, and lists them if they are different.

Diff file 1 file2 compares whether the contents of file 1 and file 2 are the same. If it is a file in text format, different contents will be displayed. If it is binary code, it can only show that the two files are different.

Comm file 1 file2 compares files and displays the different contents of the two files.

7.ln command

Function: Create a link. Windows shortcuts are based on the link principle.

Source path target path hard connection

Ln -s source path target path soft connection

Ln is another very important command in linux. Its function is to establish different links for files in another location. The most commonly used parameter of this command is -s, and the specific usage is: ln–s source file target file.

When we need to use the same file in different directories, we don't need to put the same file in every needed directory. We just need to put the files in a fixed directory, and then link them in other directories with ln command, without occupying disk space repeatedly. For example: ln–s/bin/less/usr/local/bin/less.

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Second, view the file content command.

1, cat command

Displays the contents of the file, which is the same as DOS type.

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2. More commands

Function: Paging display command