What does the blue color displayed by the linux ls command mean?

In Linux, the blue color displayed by the ls command indicates "directory". The ls command will color the file name according to the specific type of the file: 1. White represents ordinary files; 2. Bright green represents executable files; 3. Bright red represents compressed files; 4. Blue represents directories; 5. Bright blue represents Link files; 6. Bright yellow indicates device files.

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

The ls -l command (i.e. ll command) under Linux to view the display result analysis of the file

Use "ls -l" or "ls -al" under Linux Or when you use the "ll" command to view file and directory details, several columns of information will be displayed in the shell.

First give a typical display result:

The following is a detailed analysis of each column:

1. Font color

# In most Linux shell windows, colors can also be used to distinguish the attributes of different files:

• White represents ordinary files;
• Bright green represents executable files;
• Bright red represents compressed files;
• Gray blue represents directories ;
• Bright blue indicates link files;
• Bright yellow indicates device files;

Of course, the system default color scheme needs to be used here. If you customize the shell's color scheme, it may be inconsistent with the above definition.

2. File type

## indicates the type of the file:

"-" represents an ordinary file;
• "d" represents a directory;
• "l" represents a link file;
• "p" represents a management file;
• "b" represents a block device file;
• "c" represents a character device file;
• "s" represents a socket file;

3. File attributes

Taking the back_init file as an example, its attributes can be divided into three sections: [rwx][rwx] [r-x], where:

The first paragraph represents the permissions that the file creator/owner has on the file, and the second paragraph represents the permissions that other users in the group of the creator/owner have, The third paragraph indicates the permissions that other users in other groups have.

• r (Read, read permission): For files, it has the permission to read the file content; for directories, it has the permission to browse the directory .

• w (Write, write permission): For files, it has the permission to add and modify file content; for directories, it has the permission to delete, Permissions to move files within the directory.

• x (eXecute, execution permission): For files, the user has the permission to execute the file; for directories, the user has the permission to enter the directory.

  In addition, there are two very special attributes here, which are not very common in ordinary times. I will also explain them here:

• s or S (SUID, Set UID): If an executable file is matched with this permission, it can obtain privileges and arbitrarily access all system resources that can be used by the owner of the file. Please pay attention to files with SUID permissions. Hackers often use this permission to match the root account owner with SUID to silently open a backdoor in the system for future access.

• t or T (Sticky): The /tmp and /var/tmp directories are for temporary file access by all users, that is, each user has a complete Permission to enter the directory to browse, delete and move files.

To sum up, for the back_init file, its creator/owner has read, write, and executable permissions, and other users in the group of its creator/owner have Read, write, and execute permissions, while other users in other groups have read, execute, but not write permissions.

4. Number of directories/links

For a directory file, it represents its first-level subdirectory number. Note that the value seen here must be subtracted by 2 to equal the actual number of subdirectories in this directory.

• For example, in the include directory here, there are actually no subdirectories, so it should be 0, but it displays 2 here. This is because the . directory and... directory are added. Under Linux, .directory represents the current directory, and ...directory represents the upper-level directory.
• This can also explain the 3 in the directory in the first line and the 26 in the directory in the second line in the above picture. Because there is an include directory in the current directory, adding the two directories . directory and ... directory equals 3, so the first line will display 3. There are 24 directories in the upper-level directory, plus the . directory and... directory of the upper-level directory, so the second line here displays 26.

For other files, it indicates the number of link files pointing to it.

5. Owner and group

Indicates the owner/creator (owner) of the file and its The group it belongs to.

6. File size

If it is a file, it indicates the size of the file, in units of byte.
If it is a directory, it indicates the size of the directory symbol, but does not indicate the size of all files in the directory.

7. Modification date

The date and time when the file was last modified.

8. File name

File name, no need to say more.

Finally, one thing to note is that in the above picture, there is an asterisk () behind the back_init file, which is also used to mark available files under the Linux system. Another way to execute files. In other words, any file name with an asterisk () after it indicates that it is an executable file.

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