7 Agreed, the lsof man page is dense and lsof has a plethora of
8 options. There are examples, but the manual page format buries
9 them at the end. How does one get started with lsof?
11 This file is an attempt to answer that question. It plunges
12 immediately into examples of lsof use to solve problems that
13 involve looking at the open files of Unix processes.
19 2. Finding Uses of a Specific Open File
20 3. Finding Open Files Filling a File System
21 a. Finding an Unlinked Open File
22 4. Finding Processes Blocking Umount
23 5. Finding Listening Sockets
24 6. Finding a Particular Network Connection
25 7. Identifying a Netstat Connection
26 8. Finding Files Open to a Named Command
27 9. Deciphering the Remote Login Trail
29 b. The idrlogin.perl[5] Scripts
30 10. Watching an Ftp or Rcp Transfer
31 11. Listing Open NFS Files
32 12. Listing Files Open by a Specific Login
33 a. Ignoring a Specific Login
34 13. Listing Files Open to a Specific Process Group
35 14. When Lsof Seems to Hang
36 a. Kernel lstat(), readlink(), and stat() Blockages
37 b. Problems with /dev or /devices
38 c. Host and Service Name Lookup Hangs
39 d. UID to Login Name Conversion Delays
40 15. Output for Other Programs
41 16. The Lsof Exit Code and Shell Scripts
42 17. Strange messages in the NAME column
48 C. Precautionary Options
49 D. Miscellaneous Lsof Options
52 2. Finding Uses of a Specific Open File
53 ========================================
55 Often you're interested in knowing who is using a specific file.
56 You know the path to it and you want lsof to tell you the processes
57 that have open references to it.
59 Simple -- execute lsof and give it the path name of the file of
64 Caveat: this only works if lsof has permission to get the status
65 (via stat(2)) of the file at the named path. Unless the lsof
66 process has enough authority -- e.g., it is being run with a
67 real User ID (UID) of root -- this AIX example won't work:
69 Further caveat: this use of lsof will fail if the stat(2) kernel
70 syscall returns different file parameters -- particularly device
71 and inode numbers -- than lsof finds in kernel node structures.
72 This condition is rare and is usually documented in the 00FAQ
73 file of the lsof distribution.
75 $ lsof /etc/security/passwd
76 lsof: status error on /etc/security/passwd: Permission denied
79 3. Finding Open Files Filling a File System
80 ============================================
82 Oh! Oh! /tmp is filling and ls doesn't show that any large files
83 are being created. Can lsof help?
85 Maybe. If there's a process that is writing to a file that has
86 been unlinked, lsof may be able to discover the process for you.
87 You ask it to list all open files on the file system where /tmp
90 Sometimes /tmp is a file system by itself. In that case,
94 is the appropriate command. If, however, /tmp is part of another
95 file system, typically /, then you may have to ask lsof to list
96 all files open on the containing file system and locate the
97 offending file and its process by inspection -- e.g.,
103 Caveat: there must be a file open to a for the lsof search to
104 succeed. Sometimes the kernel may cause a file reference to
105 persist, even where there's no file open to a process. (Can you
106 say kernel bug? Maybe.) In any event, lsof won't be able to
109 a. Finding an Unlinked Open File
110 =================================
112 A pesky variant of a file that is filling a file system is an
113 unlinked file to which some process is still writing. When a
114 process opens a file and then unlinks it, the file's resources
115 remain in use by the process, but the file's directory entries
116 are removed. Hence, even when you know the directory where the
117 file once resided, you can't detect it with ls.
119 This can be an administrative problem when the unlinked file is
120 large, and the process that holds it open continues to write to
121 it. Only when the process closes the file will its resources,
122 particularly disk space, be released.
124 Lsof can help you find unlinked files on local disks. It has an
125 option, +L, that will list the link counts of open files. That
126 helps because an unlinked file on a local disk has a zero link
127 count. Note: this is NOT true for NFS files, accessed from a
130 You could use the option to list all files and look for a zero
131 link count in the NLINK column -- e.g.,
134 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NLINK NODE NAME
136 less 25366 abe txt VREG 6,0 40960 1 76319 /usr/...
138 > less 25366 abe 3r VREG 6,0 17360 0 98768 / (/dev/sd0a)
140 Better yet, you can specify an upper bound to the +L option, and
141 lsof will select only files that have a link count less than the
142 upper bound. For example:
145 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NLINK NODE NAME
146 less 25366 abe 3r VREG 6,0 17360 0 98768 / (/dev/sd0a)
148 You can use lsof's -a (AND) option to narrow the link count search
149 to a particular file system. For example, to look for zero link
150 counts on the /home file system, use:
154 CAUTION: lsof can't always report link counts for all file types
155 -- e.g., it may not report them for FIFOs, pipes, or sockets.
156 Remember also that link counts for NFS files on an NFS client
157 host don't behave as do link counts for files on local disks.
160 4. Finding Processes Blocking Umount
161 =====================================
163 When you need to unmount a file system with the umount command,
164 you may find the operation blocked by a process that has a file
165 open on the file systems. Lsof may be able to help you find the
166 process. In response to:
168 $ lsof <file_system_name>
170 Lsof will display all open files on the named file system. It
171 will also set its exit code zero when it finds some open files
172 and non-zero when it doesn't, making this type of lsof call
173 useful in shell scripts. (See section 16.)
175 Consult the output of the df command for file system names.
177 See the caveat in the preceding section about file references
178 that persist in the kernel without open file traces. That
179 situation may hamper lsof's ability to help with umount, too.
182 5. Finding Listening Sockets
183 =============================
185 Sooner or later you may wonder if someone has installed a network
186 server that you don't know about. Lsof can list for you all the
187 network socket files open on your machine with:
191 The -i option without further qualification lists all open Internet
192 socket files. You can add network names or addresses, protocol
193 names, and service names or port numbers to the -i option to
194 refine the search. (See the next section.)
197 6. Finding a Particular Network Connection
198 ===========================================
200 When you know the source or destination of a network connection
201 whose open files and process you'd like to identify, the -i option
204 If, for example, you want to know what process has a connection
205 open to or from the Internet host named aaa.bbb.ccc, you can ask
206 lsof to search for it with:
208 $ lsof -i@aaa.bbb.ccc
210 If you're interested in a particular protocol -- TCP or UDP --
211 and a specific port number or service name, you can add those
212 discriminators to the -i information:
214 $ lsof -iTCP@aaa.bbb.ccc:ftp-data
216 If you're interested in a particular IP version -- IPv4 or IPv6
217 -- and your UNIX dialect supports both (It does if "IPv[46]"
218 appears in the lsof -h output.), you can add the '4' or '6'
219 selector immediately after -i:
225 7. Identifying a Netstat Connection
226 ====================================
228 How do I identify the process that has a network connection
229 described in netstat output? For example, if netstat says:
231 Proto Recv-Q Send-Q Local Address Foreign Address (state)
232 tcp 0 0 vic.1023 ipscgate.login ESTABLISHED
234 What process is connected to service name ``login'' on ipscgate?
236 Use lsof's -i option:
238 $lsof -iTCP@ipscgate:login
239 COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
240 rlogin 25023 abe 3u inet 0x10144168 0t184 TCP lsof.itap.purdue.edu:1023->ipscgate.cc.purdue.edu:login
243 There's another way. Notice the 0x10144168 in the DEVICE column
244 of the lsof output? That's the protocol control block (PCB)
245 address. Many netstat applications will display it when given
249 PCB Proto Recv-Q Send-Q Local Address Foreign Address (state)
250 10144168 tcp 0 0 vic.1023 ipscgate.login ESTABLISHED
253 Using the PCB address, lsof, and grep, you can find the process this
256 $ lsof -i | grep 10144168
257 rlogin 25023 abe 3u inet 0x10144168 0t184 TCP lsof.itap.purdue.edu:1023->ipscgate.cc.purdue.edu:login
260 If the file is a UNIX socket and netstat reveals and adress for it,
261 like this Solaris 11 example:
264 Active UNIX domain sockets
265 Address Type Vnode Conn Local Addr Remote Addr
266 ffffff0084253b68 stream-ord 0000000 0000000
268 Using lsof's -U option and its output piped to a grep on the address
271 $ lsof -U | grep ffffff0084253b68
272 squid 1638 nobody 12u unix 18,98 0t10 9437188 /devices/pseudo/tl@0:ticots->0xffffff0084253b68 stream-ord
275 8. Finding Files Open to a Named Command
276 =========================================
278 When you want to look at the files open to a particular command,
279 you can look up the PID of the process running the command and
280 use lsof's -p option to specify it.
284 However, there's a quicker way, using lsof's -c option, provided
285 you don't mind seeing output for every process running the named
288 $ lsof -c <first_characters_of_command_name_that_interest_you>
290 The lsof -c option is useful when you want to see how many instances
291 of a given command are executing and what their open files are.
292 One useful example is for the sendmail command.
297 9. Deciphering the Remote Login Trail
298 ======================================
300 If the network connection you're interested in tracing has been
301 initiated externally and is connected to an rlogind, sshd, or
302 telnetd process, asking lsof to identify that process might not
303 give a wholly satisfying answer. The report may be that the
304 connection exists, but to a process owned by root.
309 How do you get from there to the login name really using the
310 connection? You have to know a little about how real and pseudo
311 ttys are paired in your system, and then use several lsof probes
312 to identify the login.
314 This example comes from a Solaris 2.4 system, named klaatu.cc.
315 I've logged on to it via rlogin from lsof.itap. The first lsof
320 yields (among other things):
322 COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
323 in.rlogin 7362 root 0u inet 0xfc0193b0 0t242 TCP klaatu.cc.purdue.edu:login->lsof.itap.purdue.edu:1023
326 This confirms that a connection exists. A second lsof probe
330 COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
332 in.rlogin 7362 root 0u inet 0xfc0193b0 0t242 TCP klaatu.cc.purdue.edu:login->lsof.itap.purdue.edu:1023
334 in.rlogin 7362 root 3u VCHR 23, 0 0t66 52928 /devices/pseudo/clone@0:ptmx->pckt->ptm
336 7362 is the Process ID (PID) of the in.rlogin process, discovered
337 in the first lsof probe. (I've abbreviated the output to simplify
338 the example.) Now comes a need to understand Solaris pseudo-ttys.
339 The key indicator is in the DEVICE column for FD 3, the major/minor
340 device number of 23,0. This translates to /dev/pts/0, so a third
344 COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
345 ksh 7364 abe 0u VCHR 24, 0 0t2410 53410 /dev/pts/../../devices/pseudo/pts@0:0
347 shows in part that login abe has a ksh process on /dev/pts/0.
348 (The NAME that lsof shows is not /dev/pts/0 but the full expansion
349 of the symbolic link that lsof finds at /dev/pts/0.)
351 Here's a second example, done on an HP-UX 9.01 host named ghg.ecn.
352 Again, I've logged on to it from lsof.itap, so I start with:
355 COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
356 rlogind 10214 root 0u inet 0x041d5f00 0t1536 TCP ghg.ecn.purdue.edu:login->lsof.itap.purdue.edu:1023
362 COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
364 rlogind 10214 root 0u inet 0x041d5f00 0t2005 TCP ghg.ecn.purdue.edu:login->lsof.itap.purdue.edu:1023
366 rlogind 10214 root 3u VCHR 16,0x000030 0t2037 24642 /dev/ptym/ptys0
368 Here the key is the NAME /dev/ptym/ptys0. In HP-UX 9.01 tty and
369 pseudo tty devices are paired with the names like /dev/ptym/ptys0
370 and /dev/pty/ttys0, so the following lsof probe is the final step.
372 $ lsof /dev/pty/ttys0
373 COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
374 ksh 10215 abe 0u VCHR 17,0x000030 0t3399 22607 /dev/pty/ttys0
377 Here's a third example for an AIX 4.1.4 system. I've used telnet
378 to connect to it from lsof.itap.purdue.edu. I start with:
380 $ lsof -i@lsof.itap.purdue.edu
381 COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
383 telnetd 15616 root 0u inet 0x05a93400 0t5156 TCP cloud.cc.purdue.edu:telnet->lsof.itap.purdue.edu:3369
385 Then I look at the telnetd process:
388 COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
390 telnetd 15616 root 0u inet 0x05a93400 0t5641 TCP cloud.cc.purdue.edu:telnet->lsof.itap.purdue.edu:3369
392 telnetd 15616 root 3u VCHR 25, 0 0t5493 103 /dev/ptc/0
394 Here the key is /dev/ptc/0. In AIX it's paired with /dev/pts/0.
395 The last probe for that shows:
398 COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
400 ksh 16642 abe 0u VCHR 26, 0 0t6461 360 /dev/pts/0
402 b. The idrlogin.perl[5] Scripts
403 ================================
405 There's another, perhaps easier way, to go about the job of
406 tracing a network connection. The lsof distribution contains
407 two Perl scripts, idrlogin.perl (Perl 4) and idrlogin.perl5
408 (Perl 5), that use lsof field output to display values for
409 shells that are parented by rlogind, sshd, or telnetd, or
410 connected directly to TCP sockets. The lsof test suite contains
411 a C library that can be adapted for use with C programs that
412 need to call lsof and process its field output.
414 The two Perl scripts use the lsof -R option; it causes the
415 paRent process ID (PPID) to be listed in the lsof output. The
416 scripts identify all shell processes -- e.g., ones whose command
417 names end in ``sh'' -- and determine if: 1) the ultimate ancestor
418 process before a PID greater than 2 (e.g., init's PID is 1) is
419 rlogind, sshd, or telnetd; or 2) the shell process has open
422 Here's an example of output from idlogin.perl on a Solaris 2.4
425 centurion: 1 = cd src/lsof4/scripts
426 centurion: 2 = ./idrlogin.perl
427 Login Shell PID Via PID TTY From
428 oboyle ksh 12640 in.telnetd 12638 pts/5 opal.cc.purdue.edu
429 icdtest ksh 15158 in.rlogind 15155 pts/6 localhost
430 sh csh 18207 in.rlogind 18205 pts/1 babylon5.cc.purdue.edu
431 root csh 18242 in.rlogind 18205 pts/1 babylon5.cc.purdue.edu
432 trouble ksh 19208 in.rlogind 18205 pts/1 babylon5.cc.purdue.edu
433 abe ksh 21334 in.rlogind 21332 pts/2 lsof.itap.purdue.edu
435 The scripts assume that its parent directory contains an
436 executable lsof. If you decide to use one of the scripts, you
437 may want to customize it for your local lsof and perl paths.
439 Note that processes executing as remote shells are also
442 Here's another example from a UnixWare 7.1.0 system.
444 tweeker: 1 = cd src/lsof4/scripts
445 tweeker: 9 = ./idrlogin.perl
446 Login Shell PID Via PID TTY From
447 abe ksh 9438 in.telnetd 9436 pts/3 lsof.itap.purdue.edu
450 10. Watching an Ftp or Rcp Transfer
451 ===================================
453 The nature of the Internet being one of unpredictable performance
454 at times, occasionally you want to know if a file transfer, being
455 done by ftp or rcp, is making any progress.
457 To use lsof for watching a file transfer, you need to know the
458 PID of the file transfer process. You can use ps to find that.
463 to examine the files open to the transfer process. Usually the
464 ftp files or interest are at file descriptors 9 and 10 or 10 and
465 11; for rcp, 3 and 4. They describe the network socket file and
468 If you want to watch only those file descriptors as the file
469 transfer progresses, try these lsof forms (for ftp in the example):
471 $ lsof -p<PID> -ad9,10 -r
473 $ lsof -p<PID> -ad10,11 -r
475 Some options need explaining:
477 -p<PID> specifies that lsof is to restrict its attention
478 to the process whose ID is <PID>. You can specify
479 a set of PIDs by separating them with commas.
481 $ lsof -p 1234,5678,9012
483 -a specifies that lsof is to AND its tests together.
484 The two tests that are specified are tests on the
485 PID and tests on file descriptions (``d9,10'').
487 d9,10 specifies that lsof is to test only file descriptors
488 9 and 10. Note that the `-' is absent, since ``-a''
489 is a unary option and can be followed immediately
490 by another lsof option.
492 -r tells lsof to list the requested open file information,
493 sleep for a default 15 seconds, then list the open
494 file information again. You can specify a different
495 time (in seconds) after -r and override the default.
496 Lsof issues a short line of equal signs between
497 each set of output to distinguish it.
499 For an rcp transfer, the above example becomes:
501 $ lsof -p<PID> -ad3,4 -r
504 11. Listing Open NFS Files
505 ==========================
507 Lsof will list all files open on remote file systems, supported
508 by an NFS server. Just use:
512 Note, however, that when run on an NFS server, lsof will not list
513 files open to the server from one of its clients. That's because
514 lsof can only examine the processes running on the machine where
515 it is called -- i.e., on the NFS server.
517 If you run lsof on the NFS client, using the -N option, it will
518 list files open by processes on the client that are on remote
522 12. Listing Files Open by a Specific Login
523 ==========================================
525 If you're interested in knowing what files the processes owned
526 by a particular login name have open, lsof can help.
530 $ lsof -u<User ID number>
532 You can specify either the login name or the UID associated with
533 it. You can specify multiple login names and UID numbers, mixed
534 together, by separating them with commas.
538 On the subject of login names and UIDs, it's worth noting that
539 lsof can be told to report either. By default it reports login
540 names; the -l option switches reporting to UIDs. You might want
541 to use -l if login name lookup is slow for some reason.
543 a. Ignoring a Specific Login
544 =============================
546 The -u option can also be used to direct lsof to ignore a
547 specific login name or UID, or a list of them. Simply prefix
548 the login names or UIDs with a `^' character, as you might do
549 in a regular expression. The `^' prefix is useful, for example,
550 when you want to have lsof ignore the files open to system
551 processes, owned by the root (UID 0) login. Try:
558 13. Listing Files Open to a Specific Process Group
559 ==================================================
561 There's a Unix collection of processes called a process group.
562 The name indicates that the processes of the group have a common
563 association and are grouped so that a signal sent to one (e.g.,
564 a keyboard kill stroke) is delivered to all.
566 This causes Unix to create a two element process group:
570 You can use lsof to look at the open files of all members of a
571 process group, if you know the process group ID number. Assuming
572 that it is 12717 for the above example, this lsof command:
574 $ lsof -g12717 -adcwd
576 would produce on a Solaris 8 system:
578 $ lsof -g12717 -adcwd
579 COMMAND PID PGID USER FD TYPE DEVICE SIZE/OFF NODE NAME
580 sshd 11369 12717 root cwd VDIR 0,2 189 1449175 /tmp (swap)
581 sshd 12717 12717 root cwd VDIR 136,0 1024 2 /
583 The ``-g12717'' option specifies the process group ID of interest;
584 the ``-adcwd'' option specifies that options are to be ANDed and
585 that lsof should limit file output to information about current
586 working directory (``cwd'') files.
589 14. When Lsof Seems to Hang
590 ===========================
592 On occasion when you run lsof it seems to hang and produce no
593 output. This may result from system conditions beyond the control
594 of lsof. Lsof has a number of options that may allow you to
597 a. Kernel lstat(), readlink(), and stat() Blockages
598 ====================================================
600 Lsof uses the kernel (system) calls lstat(), readlink(), and
601 stat() to locate mounted file system information. When a file
602 system has been mounted from an NFS server and that server is
603 temporarily unavailable, the calls lsof uses may block in the
606 Lsof will announce that it is being blocked with warning messages
607 (unless they have been suppressed by the lsof builder), but
608 only after a default waiting period of fifteen seconds has
609 expired for each file system whose server is unavailable. If
610 you have a number of such file systems, the total wait may be
613 You can do two things to shorten your suffering: 1) reduce the
614 wait time with the -S option; or 2) tell lsof to avoid the
615 kernel calls that might block by specifying the -b option.
621 Avoiding the kernel calls that might block may result in the
622 lack of some information that lsof needs to know about mounted
623 file systems. Thus, when you use -b, lsof warns that it might
624 lack important information.
626 The warnings that result from using -b (unless suppressed by
627 the lsof builder) can themselves be annoying. You can suppress
628 them by adding the -w option. (Of course, if you do, you won't
629 know what warning messages lsof might have issued.)
633 Note: if the lsof builder suppressed warning message issuance,
634 you don't need to use -w to suppress them. You can tell what
635 the default state of message warning issuance is by looking at
636 the -h (help) output. If it says ``-w enable warnings'' then
637 warnings are disabled by default; ``-w disable warnings'', they
638 are enabled by default.
640 b. Problems with /dev or /devices
641 ==================================
643 Lsof scans the /dev or /devices branch of your file system to
644 obtain information about your system's devices. (The scan isn't
645 necessary when a device cache file exists.)
647 Sometimes that scan can take a very long time, especially if
648 you have a large number of devices, and if your kernel is
649 relatively slow to process the stat() system call on device
650 nodes. You can't do anything about the stat() system call
653 However, you can make sure that lsof is allowed to use its
654 device cache file feature. When lsof can use a device cache
655 file, it retains information it gleans via the stat() calls
656 on /dev or /devices in a separate file for later, faster
659 The device cache file feature is described in the lsof man
660 page. See the DEVICE CACHE FILE, LSOF PERMISSIONS THAT AFFECT
661 DEVICE CACHE FILE ACCESS, DEVICE CACHE FILE PATH FROM THE -D
662 OPTION, DEVICE CACHE PATH FROM AN ENVIRONMENT VARIABLE,
663 SYSTEM-WIDE DEVICE CACHE PATH, PERSONAL DEVICE CACHE PATH
664 (DEFAULT), and MODIFIED PERSONAL DEVICE CACHE PATH sections.
666 There is also a separate file in the lsof distribution, named
667 00DCACHE, that describes the device cache file in detail,
668 including information about possible security problems.
670 One final observation: don't overlook the possibility that your
671 /dev or /devices tree might be damaged. See if
677 completes or hangs. If it hangs, then lsof will probably hang,
678 too, and you should try to discover why ls hangs.
680 c. Host and Service Name Lookup Hangs
681 ======================================
683 Lsof can hang up when it tries to convert an Internet dot-form
684 address to a host name, or a port number to a service name. Both
685 hangs are caused by the lookup functions of your system.
687 An independent check for both types of hangs can be made with
688 the netstat program. Run it without arguments. If it hangs,
689 then it is probably having lookup difficulties. When you run
690 it with -n it shouldn't hang and should report network and port
691 numbers instead of names.
693 Lsof has two options that serve the same purpose as netstat's
694 -n option. The lsof -n option tells it to avoid host name
695 lookups; and -P, service name lookups. Try those options when
696 you suspect lsof may be hanging because of lookup problems.
704 d. UID to Login Name Conversion Delays
705 =======================================
707 By default lsof converts User IDentification (UID) numbers to
708 login names when it produces output. That conversion process
709 may sometimes hang because of system problems or interlocks.
711 You can tell lsof to skip the lookup with the -l option; it
712 will then report UIDs in the USER column.
717 15. Output for Other Programs
718 =============================
720 The -F option allows you to specify that lsof should describe
721 open files with a special form of output, called field output,
722 that can be parsed easily by a subsequent program. The lsof
723 distribution comes with sample AWK, Perl 4, and Perl 5 scripts
724 that post-process field output. The lsof test suite has a C
725 library that could be adapted for use by C programs that want to
726 process lsof field output from an in-bound pipe.
728 The lsof manual page describes field output in detail in its
729 OUTPUT FOR OTHER PROGRAMS section. A quick look at a sample
730 script in the scripts/ subdirectory of the lsof distribution will
731 also give you an idea how field output works.
733 The most important thing about field output is that it is relatively
734 homogeneous across Unix dialects. Thus, if you write a script
735 to post-process field output for AIX, it probably will work for
736 HP-UX, Solaris, and Ultrix as well.
739 16. The Lsof Exit Code and Shell Scripts
740 ========================================
742 When lsof exits successfully it returns an exit code based on
743 the result of its search for specified files. (If no files were
744 specified, then the successful exit code is 0 (zero).)
746 If lsof was asked to search for specific files, including any
747 files on specified file systems, it returns an exit code of 0
748 (zero) if it found all the specified files and at least one file
749 on each specified file system. Otherwise it returns a 1 (one).
751 If lsof detects an error and makes an unsuccessful exit, it
752 returns an exit code of 1 (one).
754 You can use the exit code in a shell script to search for files
755 on a file system and take action based on the result -- e.g.,
758 lsof <file_system_name> > /dev/null 2>&1
761 echo "<file_system_name> has some users."
763 echo "<file_system_name> may have no users."
767 17. Strange messages in the NAME column
768 =======================================
770 When lsof encounters problems analyzing a particular file, it may
771 put a message in the file's NAME column. Many of those messages
772 are explained in the 00FAQ file of the lsof distribution.
774 So consult 00FAQ first if you encounter a NAME column message you
775 don't understand. (00FAQ is a possible source of information
776 about other unfamiliar things in lsof output, too.)
778 If you can't find help in 00FAQ, you can use grep to look in the
779 lsof source files for the message -- e.g.,
781 $ cd .../lsof_4.76_src
782 $ grep "can't identify protocol" *.[ch]
784 The code associated with the message will usually make clear the
785 reason for the message.
787 If you have an lsof source tree that has been processed by the
788 lsof Configure script, you need grep only there. If, however,
789 your source tree hasn't been processed by Configure, you may
790 have to look in the top-level lsof source directory and in the
791 dialects sub-directory for the UNIX dialect you are using - e.g.,
793 $ cd .../lsof_4.76_src
794 $ grep "can't identify protocol" *.[ch]
796 $ grep "can't identify protocol" *.[ch]
798 In rare cases you may have to look in the lsof library, too --
801 $ cd .../lsof_4.76_src
802 $ grep "can't identify protocol" *.[ch]
804 $ grep "can't identify protocol" *.[ch]
806 $ grep "can't identify protocol" *.[ch]
812 The following appendices describe the lsof options in detail.
818 Lsof has a rich set of options for selecting the files to be
819 displayed. These include:
821 -a tells lsof to AND the set of selection options that
822 are specified. Normally lsof ORs them.
824 For example, if you specify the -p<PID> and -u<UID>
825 options, lsof will display all files for the
826 specified PID or for the specified UID.
828 By adding -a, you specify that the listed files
829 should be limited to PIDs owned by the specified
830 UIDs -- i.e., they match the PIDs *and* the UIDs.
832 $ lsof -p1234 -au 5678
834 -c specifies that lsof should list files belonging
835 to processes having the associated command name.
837 Hint: if you want to select files based on more than
838 one command name, use multiple -c<name> specifications.
842 -d tells lsof to select by the associated file descriptor
843 (FD) set. An FD set is a comma-separated list of
844 numbers and the names lsof normally displays in
845 its FD column: cwd, Lnn, ltx, <number>, etc. See
846 the OUTPUT section of the lsof man page for the
847 complete list of possible file descriptors. Example:
851 -g tells lsof to select by the associated process
852 group ID (PGID) set. The PGID set is a comma-separated
853 list of PGID numbers. When -g is specified, it also
854 enables the display of PGID numbers.
856 Note: when -g isn't followed by a PGID set, it
857 simply selects the listing of PGID for all processes.
863 -i tells lsof to display Internet socket files. If no
864 protocol/address/port specification follows -i,
865 lsof lists all Internet socket files.
867 If a specification follows -i, lsof lists only the
868 socket files whose Internet addresses match the
871 Hint: multiple addresses may be specified with
872 multiple -i options. Examples:
875 $ lsof -i@lsof.itap.purdue.edu:sendmail
877 -N selects the listing of files mounted on NFS devices.
879 -U selects the listing of socket files in the Unix
886 Lsof has these options to control its output format:
888 -F produce output that can be parsed by a subsequent
891 -g print process group (PGID) IDs.
893 -l list UID numbers instead of login names.
895 -n list network numbers instead of host names.
897 -o always list file offset.
899 -P list port numbers instead of port service names.
901 -s always list file size.
904 C. Precautionary Options
905 =========================
907 Lsof uses system functions that can block or take a long time,
908 depending on the health of the Unix dialect supporting it. These
911 -b directs lsof to avoid system functions -- e.g.,
912 lstat(2), readlink(2), stat(2) -- that might block
913 in the kernel. See the BLOCKS AND TIMEOUTS
914 section of the lsof man page.
916 You might want to use this option when you have
917 a mount from an NFS server that is not responding.
919 -C tells lsof to ignore the kernel's name cache. As
920 a precaution this option will have little effect on
921 lsof performance, but might be useful if the kernel's
922 name cache is scrambled. (I've never seen that
925 -D might be used to direct lsof to ignore an existing
926 device cache file and generate a new one from /dev
927 (and /devices). This might be useful if you have
928 doubts about the integrity of an existing device
931 -l tells lsof to list UID numbers instead of login
932 names -- this is useful when UID to login name
933 conversion is slow or inoperative.
935 -n tells lsof to avoid converting Internet addresses
936 to host numbers. This might be useful when your
937 host name lookup (e.g., DNS) is inoperative.
939 -O tells lsof to avoid its strategy of forking to
940 perform potentially blocking kernel operations.
941 While the forking allows lsof to detect that a
942 block has occurred (and possibly break it), the
943 fork operation is a costly one. Use the -O option
944 with care, lest your lsof be blocked.
946 -P directs lsof to list port numbers instead of trying
947 to convert them to port service names. This might
948 be useful if port to service name lookups (e.g.,
949 via NIS) are slow or failing.
951 -S can be used to change the lstat/readlink/stat
952 timeout interval that governs how long lsof waits
953 for response from the kernel. This might be useful
954 when an NFS server is slow or unresponsive. When
955 lsof times out of a kernel function, it may have
956 less information to display. Example:
960 -w tells lsof to avoid issuing warning messages, if
961 they are enabled by default, or enable them if they
962 are disabled by default. Check the -h (help) output
963 to determine their status. If it says ``-w enable
964 warnings'', then warning messages are disabled by
965 default; ``-w disable warnings'', they are enabled
968 This may be a useful option, for example, when you
969 specify -b, if warning messages are enabled, because
970 it will suppress the warning messages lsof issues
971 about avoiding functions that might block in the
975 D. Miscellaneous Lsof Options
976 ==============================
978 There are some lsof options that are hard to classify, including:
980 -? these options select help output.
983 -F selects field output. Field output is a mode where
984 lsof produces output that can be parsed easily by
985 subsequent programs -- e.g., AWK or Perl scripts.
986 See ``15. Output for Other Programs'' for more
989 -k specifies an alternate kernel symbol file -- i.e.,
990 where nlist() will get its information. Example:
992 $ lsof -k/usr/crash/vmunix.1
994 -m specifies an alternate kernel memory file from
995 which lsof will read kernel structures in place
996 of /dev/kmem or kvm_read(). Example:
998 $ lsof -m/usr/crash/vmcore.n
1000 -r tells lsof to repeat its scan every 15 seconds (the
1001 default when no associated value is specified). A
1002 repeat time, different from the default, can follow
1007 -v displays information about the building of the
1010 -- The double minus sign option may be used to
1011 signal the end of options. It's particularly useful
1012 when arguments to the last option are optional and
1013 you want to supply a file path that could be confused
1014 for arguments to the last option. Example:
1018 Where `1' is a file path, not PGID ID 1.
1021 Vic Abell <abe@purdue.edu>