lsof – command

lsof command lists open files. This command has a vital role in server administration. This command reveals the files which are opened by a process. In Linux/Unix, everything is considered as a file such as pipes, sockets, devices etc are treated as files. Thus, by using ‘lsof’ command we will get the information of any opened files.


You can see some columns such as command, PID, user, FD, TYPE etc

FD – File descriptor

Some of the values in FD are :-
cwd – Current working directory
txt – Text file
mem – Memory Mapped file
mmap – Memory Mapped device
Number – It represent the actual file descriptor. For example, 0u, 1w and 3r

r = represents read, w = represents write and u = represents both read and write.

Type represents type of the file. Some of the values of TYPE are :-

>REG – Regular file
>DIR – Directory
>CHR – Character special file
>FIFO – First in first out

To list user specific opened files

#lsof -u user_name

Process running on a port

# lsof -i :port_number

Lists only IPv4 and IPv6 open files

#lsof -i 4 – For IPv4
#lsof -i 6 – For IPv6

Lists open files for TCP port ranges 1-1024

#lsof -i :1-1024

Lists by pid

#lsof -p PID

Kill all activity for a particular user

#killall -9 `lsof -t -u username`

Opened files in a directory

#lsof +D path_of_the_directory

Opened files based on process names

#lsof -c process_name

List all network connections

#lsof -i


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