lsof

lsof

Developer(s)	Vic Abell
Stable release	4.82 / March 25, 2009 (2009-03-25)
Repository	github.com/lsof-org/lsof
License	BSD license-compatible
Website	http://people.freebsd.org/~abe/

lsof is a command meaning "list open files", which is used in many Unix-like systems to report a list of all open files and the processes that opened them. This open source utility was developed and supported by Vic Abell, the retired Associate Director of the Purdue University Computing Center. It works in and supports several Unix flavors.

Open files in the system include disk files, pipes, network sockets and devices opened by all processes. One use for this command is when a disk cannot be unmounted because (unspecified) files are in use. The listing of open files can be consulted (suitably filtered if necessary) to identify the process that is using the files.

 # lsof /var
 COMMAND     PID     USER   FD   TYPE DEVICE SIZE/OFF     NODE NAME
 syslogd     350     root    5w  VREG  222,5        0 440818 /var/adm/messages
 syslogd     350     root    6w  VREG  222,5   339098   6248 /var/log/syslog
 cron        353     root  cwd   VDIR  222,5      512 254550 /var -- atjobs

To view the port associated with a daemon:

  # lsof -i -n -P | grep sendmail
  sendmail  31649    root    4u  IPv4 521738       TCP *:25 (LISTEN)

From the above we can see that "sendmail" is listening on its standard port of "25".

• -i Lists IP sockets.
• -n Do not resolve hostnames (no DNS).
• -P Do not resolve port names (list port number instead of its name).

See also

• stat (Unix)
• netstat
• strace
• List of Unix programs
• Process Explorer from SysInternals - the equivalent for Windows (Find menu -> Find Handle or DLL)

External links

• lsof manpage on www.netadmintools.com
• Troubleshooting Runnings Systems with lsof
• Lsof FAQ [1]
• Sam Nelson's PCP script, an alternative to "lsof -i" for Solaris.