What are the permission settings for debian readdir

In Debian system, the readdir function is used to list the contents of the directory. Although readdir itself does not directly handle file system permissions, the permissions of the directory will directly affect whether it can be read successfully.

Key Permissions:

1. Read permissions (r): readdir requires read permissions from the directory to work. Missing read permission will cause readdir to fail. Use commands such as chmod or directory_name (add read permissions for other users) to modify permissions.

2. Execution permission (x): Even if you have read permission, if you do not have execution permission, you cannot enter the directory, readdir will also fail. Use commands such as chmod ox directory_name (add execution permissions for other users) to modify permissions.

User and Group Permissions:

The standard Unix permission model (owner (u), group (g), others (o)) also applies to directories, which determines the access rights of different user groups to directories.

Special permissions:

• setgid bit: After setting this bit, the new directory created under this directory will inherit the group ID of the parent directory.
• sticky bit: This is mainly used in multi-user environments to prevent users from deleting or renaming files that do not belong to themselves.

Permission setting example:

Assume the directory name is mydir :

 # View current permissions ls -ld mydir

# Only allow owners to access chmod 700 mydir

# Owner and group can read and write execution, other users can only read chmod 755 mydir

# Add setgid bit chmod gs mydir

# Add sticky bit chmod t mydir

Important tips:

• Be careful when modifying permissions to avoid accidentally restricting access to legitimate users.
• The umask command can set default permissions to create files and directories.
• Follow the principle of minimum permissions and only the necessary permissions are granted.

Summary: The successful execution of readdir function depends on the read (r) and execution (x) permissions of the target directory, as well as the user/group permission settings. Ensuring that the target directory has the correct permission configuration is the key to the normal operation of readdir .

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