Some common commands and usage under Unix-like systems.

utility command

chown

Change file owner and group.

For example, the current owner of a folder is root and needs to be changed to admin:

chown -R admin:admin test

chmod

Modify file permissions.

fuser

See who owns the file.

fuser -u .linux.md.swp

id

View current user, group id.

lsof

View a list of open files.

An open file may be a regular file, a directory, a block special file, a character special file, an executing text reference, a library, a stream or a network file (Internet socket, NFS file or UNIX domain socket.) A specific file or all the files in a file system may be selected by path.

View network-related file usage

lsof -i

View port usage

lsof -i tcp:5037

Check who owns a file

lsof.linux.md.swp

View the file information occupied by a user

lsof -u mazhuang

-u can be followed by uid or login name.

View the file information occupied by a program

lsof -c Vim

Note that program names are case sensitive.