Lsof

Internal

• Linux

Overview

lsof lists information about files opened by processes. lsof provides information about:

• regular files
• directories
• block special files
• character special files
• executing text references
• libraries
• streams
• network files (Internet socket, NFS file or UNIX domain socket)

In absence of any options, lsof lists all open files by all processes.

To list open files by a specific process, use the process' PID as follows:

lsof -p <pid>

The output is similar to:

COMMAND   PID    USER   FD   TYPE             DEVICE SIZE/OFF    NODE NAME
java    10016 vagrant  cwd    DIR              252,2     4096 2621584 /home/test
java    10016 vagrant  rtd    DIR              252,0     4096       2 /
java    10016 vagrant  txt    REG              252,2     7734 2885001 /opt/java/x64/jre1.8.0_51/bin/java
java    10016 vagrant  mem    REG              252,0   161704 1310723 /lib64/ld-2.12.so
[...]
java    10016 vagrant    0r   CHR                1,3      0t0      26 /dev/null
java    10016 vagrant    1u   CHR              136,0      0t0       3 /dev/pts/0 (deleted)
java    10016 vagrant    2u   CHR              136,0      0t0       3 /dev/pts/0 (deleted)
java    10016 vagrant    3w   REG              252,2    48759 2753619 /home/test/gc.log.0.current
java    10016 vagrant    4r   REG              252,2 65944582 2884909 /opt/java/x64/jre1.8.0_51/lib/rt.jar
java    10016 vagrant    5u  IPv4              39331      0t0     TCP *:msgsrvr (LISTEN)
[...]

File Descriptor Information

The command provides file descriptor information by default, as the fourth field "FD". The FD column contents constitutes a single field for parsing in post-processing scripts.

The FD column content if the file descriptor number, followed by one of these characters, describing the mode under which the file is open:

• 'r' for read access
• 'w' for write access
• 'u' for read and write access
• space if mode is unknown and no lock character follows
• ‘-’ if mode unknown and lock character follows

The mode character is followed by one of these lock characters, describing the type of lock applied to the file:

• 'r' for read lock on part of the file
• 'R' for a read lock on the entire file
• 'w' for a write lock on part of the file
• 'W' for a write lock on the entire file
• 'u' for a read and write lock of any length
• 'U' for a lock of unknown type
• space if there is no lock

Special entries do not start with a file descriptor number and marked as such:

• cwd current working directory
• err FD information error (see NAME column)
• jld" jail directory (FreeBSD)
• ltx shared library text (code and data)
• Mxx hex memory-mapped type number xx
• m86 DOS Merge mapped file
• mem memory-mapped file
• mmap memory-mapped device
• pd parent directory
• rtd root directory
• tr kernel trace file (OpenBSD)
• txt program text (code and data)
• v86 VP/ix mapped file