neulab/tldr huggingface dataset:
-u s     selects the listing of files for the user whose login names or user ID numbers are in the comma-separated set s - e.g., ``abe'', or ``548,root''.  (There should be no spaces in the set.)
Multiple login names or user ID numbers are joined in a single ORed set before participating in AND option selection.
If a login name or user ID is preceded by a `^', it becomes a negation - i.e., files of processes owned by the login name or user ID will never be listed.  A negated login name or user ID selection is neither ANDed nor ORed with other selections; it is applied before all other selections and absolutely excludes the listing of the files of the process.  For example, to direct lsof to exclude the listing of files belonging to root processes, specify ``-u^root'' or ``-u^0''.
-U       selects the listing of UNIX domain socket files.
-v       selects the listing of lsof version information, including: revision number; when the lsof binary was constructed; who constructed the binary and where; the name of the compiler used to construct the lsof binary; the version number of the compiler when readily available; the compiler and loader flags used to construct the lsof binary; and system information, typically the output of uname's -a option.
-V       directs lsof to indicate the items it was asked to list and failed to find - command names, file names, Internet addresses or files, login names, NFS files, PIDs, PGIDs, and UIDs.
When other options are ANDed to search options, or compile-time options restrict the listing of some files, lsof may not report that it failed to find a search item when an ANDed option or compile-time option prevents the listing of the open file containing the located search item.
For example, ``lsof -V -iTCP@foobar -a -d 999'' may not report a failure to locate open files at ``TCP@foobar'' and may not list any, if none have a file descriptor number of 999.  A similar situation arises when HASSECURITY and HASNOSOCKSECURITY are defined at compile time and they prevent the listing of open files.
+|-w     Enables (+) or disables (-) the suppression of warning messages.
The lsof builder may choose to have warning messages disabled or enabled by default.  The default warning message state is indicated in the output of the -h or -?  option.  Disabling warning messages when they are already disabled or enabling them when already enabled is acceptable.
-x [fl]  may accompany the +d and +D options to direct their processing to cross over symbolic links and|or file system mount points encountered when scanning the directory (+d) or directory tree (+D).
If -x is specified by itself without a following parameter, cross-over processing of both symbolic links and file system mount points is enabled.  Note that when -x is specified without a parameter, the next argument must begin with '-' or '+'.
The optional 'f' parameter enables file system mount point cross-over processing; 'l', symbolic link cross-over processing.
The -x option may not be supplied without also supplying a +d or +D option.
-X       This is a dialect-specific option.
AIX: This IBM AIX RISC/System 6000 option requests the reporting of executed text file and shared library references.
WARNING: because this option uses the kernel readx() function, its use on a busy AIX system might cause an application process to hang so completely that it can neither be killed nor stopped. I have never seen this happen or had a report of its happening, but I think there is a remote possibility it could happen.
By default use of readx() is disabled.  On AIX 5L and above lsof may need setuid-root permission to perform the actions this option requests.
The lsof builder may specify that the -X option be restricted to processes whose real UID is root.  If that has been done, the -X option will not appear in the -h or -?  help output unless the real UID of the lsof process is root.  The default lsof distribution allows any UID to specify -X, so by default it will appear in the help output.
When AIX readx() use is disabled, lsof may not be able to report information for all text and loader file references, but it may also avoid exacerbating an AIX kernel directory search kernel error, known as the Stale Segment ID bug.
The readx() function, used by lsof or any other program to access some sections of kernel virtual memory, can trigger the Stale Segment ID bug.  It can cause the kernel's dir_search() function to believe erroneously that part of an in-memory copy of a file system directory has been zeroed.  Another application process, distinct from lsof, asking the kernel to search the directory - e.g., by using open(2) - can cause dir_search() to loop forever, thus hanging the application process.
Consult the lsof FAQ (The FAQ section gives its location.)  and the 00README file of the lsof distribution for a more complete description of the Stale Segment ID bug, its APAR, and methods for defining readx() use when compiling lsof.
Linux: This Linux option requests that lsof skip the reporting of information on all open TCP, UDP and UDPLITE IPv4 and IPv6 files.
This Linux option is most useful when the system has an extremely large number of open TCP, UDP and UDPLITE files, the processing of whose information in the /proc/net/tcp* and /proc/net/udp* files would take lsof a long time, and whose reporting is not of interest.
Use this option with care and only when you are sure that the information you want lsof to display isn't associated with open TCP, UDP or UDPLITE socket files.
Solaris 10 and above: This Solaris 10 and above option requests the reporting of cached paths for files that have been deleted - i.e., removed with rm(1) or unlink(2).
The cached path is followed by the string `` (deleted)'' to indicate that the path by which the file was opened has been deleted.
Because intervening changes made to the path - i.e., renames with mv(1) or rename(2) - are not recorded in the cached path, what lsof reports is only the path by which the file was opened, not its possibly different final path.
-z [z]   specifies how Solaris 10 and higher zone information is to be handled.
Without a following argument - e.g., NO z - the option specifies that zone names are to be listed in the ZONE output column.
The -z option may be followed by a zone name, z.  That causes lsof to list only open files for processes in that zone. Multiple -z z option and argument pairs may be specified to form a list of named zones.  Any open file of any process in any of the zones will be listed, subject to other conditions specified by other options and arguments.
-Z [Z]   specifies how SELinux security contexts are to be handled.  It and 'Z' field output character support are inhibited when SELinux is disabled in the running Linux kernel.  See OUTPUT FOR OTHER PROGRAMS for more information on the 'Z' field output character.
Without a following argument - e.g., NO Z - the option specifies that security contexts are to be listed in the SECURITY-CONTEXT output column.
The -Z option may be followed by a wildcard security context name, Z.  That causes lsof to list only open files for processes in that security context.  Multiple -Z Z option and argument pairs may be specified to form a list of security contexts.  Any open file of any process in any of the security contexts will be listed, subject to other conditions specified by other options and arguments.  Note that Z can be A:B:C or *:B:C or A:B:* or *:*:C to match against the A:B:C context.
--       The double minus sign option is a marker that signals the end of the keyed options.  It may be used, for example, when the first file name begins with a minus sign.  It may also be used when the absence of a value for the last keyed option must be signified by the presence of a minus sign in the following option and before the start of the file names.
names    These are path names of specific files to list.  Symbolic links are resolved before use.  The first name may be separated from the preceding options with the ``--'' option.
If a name is the mounted-on directory of a file system or the device of the file system, lsof will list all the files open on the file system.  To be considered a file system, the name must match a mounted-on directory name in mount(8) output, or match the name of a block device associated with a mounted-on directory name.  The +|-f option may be used to force lsof to consider a name a file system identifier (+f) or a simple file (-f).
If name is a path to a directory that is not the mounted-on directory name of a file system, it is treated just as a regular file is treated - i.e., its listing is restricted to processes that have it open as a file or as a process-specific directory, such as the root or current working directory.  To request that lsof look for open files inside a directory name, use the +d s and +D D options.
If a name is the base name of a family of multiplexed files - e.g, AIX's /dev/pt[cs] - lsof will list all the associated multiplexed files on the device that are open - e.g., /dev/pt[cs]/1, /dev/pt[cs]/2, etc.
If a name is a UNIX domain socket name, lsof will usually search for it by the characters of the name alone - exactly as it is specified and is recorded in the kernel socket structure.  (See the next paragraph for an exception to that rule for Linux.) Specifying a relative path - e.g., ./file - in place of the file's absolute path - e.g., /tmp/file - won't work because lsof must match the characters you specify with what it finds in the kernel UNIX domain socket structures.
If a name is a Linux UNIX domain socket name, in one case lsof is able to search for it by its device and inode number, allowing name to be a relative path.  The case requires that the absolute path -- i.e., one beginning with a slash ('/') be used by the process that created the socket, and hence be stored in the /proc/net/unix file; and it requires that lsof be able to obtain the device and node numbers of both the absolute path in /proc/net/unix and name via successful stat(2) system calls. When those conditions are met, lsof will be able to search for the UNIX domain socket when some path to it is is specified in name.  Thus, for example, if the path is /dev/log, and an lsof search is initiated when the working directory is /dev, then name could be ./log.
If a name is none of the above, lsof will list any open files whose device and inode match that of the specified path name.
If you have also specified the -b option, the only names you may safely specify are file systems for which your mount table supplies alternate device numbers.  See the AVOIDING KERNEL BLOCKS and ALTERNATE DEVICE NUMBERS sections for more information.
Multiple file names are joined in a single ORed set before participating in AND option selection.
Lsof supports the recognition of AFS files for these dialects (and AFS versions):
AIX 4.1.4 (AFS 3.4a) HP-UX 9.0.5 (AFS 3.4a) Linux 1.2.13 (AFS 3.3) Solaris 2.[56] (AFS 3.4a)
It may recognize AFS files on other versions of these dialects, but has not been tested there.  Depending on how AFS is implemented, lsof may recognize AFS files in other dialects, or may have difficulties recognizing AFS files in the supported dialects.
Lsof may have trouble identifying all aspects of AFS files in supported dialects when AFS kernel support is implemented via dynamic modules whose addresses do not appear in the kernel's variable name list.  In that case, lsof may have to guess at the identity of AFS files, and might not be able to obtain volume information from the kernel that is needed for calculating AFS volume node numbers.  When lsof can't compute volume node numbers, it reports blank in the NODE column.
The -A A option is available in some dialect implementations of lsof for specifying the name list file where dynamic module kernel addresses may be found.  When this option is available, it will be listed in the lsof help output, presented in response to the -h or -?
See the lsof FAQ (The FAQ section gives its location.)  for more information about dynamic modules, their symbols, and how they affect lsof options.
Because AFS path lookups don't seem to participate in the kernel's name cache operations, lsof can't identify path name components for AFS files.
Lsof has three features that may cause security concerns.  First, its default compilation mode allows anyone to list all open files with it. Second, by default it creates a user-readable and user-writable device cache file in the home directory of the real user ID that executes lsof. (The list-all-open-files and device cache features may be disabled when lsof is compiled.)  Third, its -k and -m options name alternate kernel name list or memory files.
Restricting the listing of all open files is controlled by the compile-time HASSECURITY and HASNOSOCKSECURITY options.  When HASSECURITY is defined, lsof will allow only the root user to list all open files. The non-root user may list only open files of processes with the same user IDentification number as the real user ID number of the lsof process (the one that its user logged on with).
However, if HASSECURITY and HASNOSOCKSECURITY are both defined, anyone may list open socket files, provided they are selected with the -i option.
When HASSECURITY is not defined, anyone may list all open files.
Help output, presented in response to the -h or -?  option, gives the status of the HASSECURITY and HASNOSOCKSECURITY definitions.
See the Security section of the 00README file of the lsof distribution for information on building lsof with the HASSECURITY and HASNOSOCKSECURITY options enabled.
Creation and use of a user-readable and user-writable device cache file is controlled by the compile-time HASDCACHE option.  See the DEVICE CACHE FILE section and the sections that follow it for details on how its path is formed.  For security considerations it is important to note that in the default lsof distribution, if the real user ID under which lsof is executed is root, the device cache file will be written in root's home directory - e.g., / or /root.  When HASDCACHE is not defined, lsof does not write or attempt to read a device cache file.
When HASDCACHE is defined, the lsof help output, presented in response to the -h, -D?, or -?  options, will provide device cache file handling information.  When HASDCACHE is not defined, the -h or -?  output will have no -D option description.
Before you decide to disable the device cache file feature - enabling it improves the performance of lsof by reducing the startup overhead of examining all the nodes in /dev (or /devices) - read the discussion of it in the 00DCACHE file of the lsof distribution and the lsof FAQ (The FAQ section gives its location.)
WHEN IN DOUBT, YOU CAN TEMPORARILY DISABLE THE USE OF THE DEVICE CACHE FILE WITH THE -Di OPTION.
When lsof user declares alternate kernel name list or memory files with the -k and -m options, lsof checks the user's authority to read them with access(2).  This is intended to prevent whatever special power lsof's modes might confer on it from letting it read files not normally accessible via the authority of the real user ID.
This section describes the information lsof lists for each open file. See the OUTPUT FOR OTHER PROGRAMS section for additional information on output that can be processed by another program.
Lsof only outputs printable (declared so by isprint(3)) 8 bit characters. Non-printable characters are printed in one of three forms: the C ``\[bfrnt]'' form; the control character `^' form (e.g., ``^@''); or hexadecimal leading ``\x'' form (e.g., ``\xab'').  Space is non-printable in the COMMAND column (``\x20'') and printable elsewhere.
For some dialects - if HASSETLOCALE is defined in the dialect's machine.h header file - lsof will print the extended 8 bit characters of a language locale.  The lsof process must be supplied a language locale environment variable (e.g., LANG) whose value represents a known language locale in which the extended characters are considered printable by isprint(3). Otherwise lsof considers the extended characters non-printable and prints them according to its rules for non-printable characters, stated above. Consult your dialect's setlocale(3) man page for the names of other environment variables that may be used in place of LANG - e.g., LC_ALL, LC_CTYPE, etc.
Lsof's language locale support for a dialect also covers wide characters - e.g., UTF-8 - when HASSETLOCALE and HASWIDECHAR are defined in the dialect's machine.h header file, and when a suitable language locale has been defined in the appropriate environment variable for the lsof process.  Wide characters are printable under those conditions if iswprint(3) reports them to be.  If HASSETLOCALE, HASWIDECHAR and a suitable language locale aren't defined, or if iswprint(3) reports wide characters that aren't printable, lsof considers the wide characters non-printable and prints each of their 8 bits according to its rules for non-printable characters, stated above.
Consult the answers to the "Language locale support" questions in the lsof FAQ (The FAQ section gives its location.) for more information.
Lsof dynamically sizes the output columns each time it runs, guaranteeing that each column is a minimum size.  It also guarantees that each column is separated from its predecessor by at least one space.
COMMAND    contains the first nine characters of the name of the UNIX command associated with the process.  If a non-zero w value is specified to the +c w option, the column contains the first w characters of the name of the UNIX command associated with the process up to the limit of characters supplied to lsof by the UNIX dialect.  (See the description of the +c w command or the lsof FAQ for more information.  The FAQ section gives its location.)
If a zero w value is specified to the +c w option, the column contains all the characters of the name of the UNIX command associated with the process.
All command name characters maintained by the kernel in its structures are displayed in field output when the command name descriptor (`c') is specified.  See the OUTPUT FOR OTHER COMMANDS section for information on selecting field output and the associated command name descriptor.
PID        is the Process IDentification number of the process.
TID        is the task (thread) IDentification number, if task (thread) reporting is supported by the dialect and a task (thread) is being listed.  (If help output - i.e., the output of the -h or -?  options - shows this option, then task (thread) reporting is supported by the dialect.)
A blank TID column in Linux indicates a process - i.e., a non-task.
TASKCMD    is the task command name.  Generally this will be the same as the process named in the COMMAND column, but some task implementations (e.g., Linux) permit a task to change its command name.
The TASKCMD column width is subject to the same size limitation as the COMMAND column.
ZONE       is the Solaris 10 and higher zone name.  This column must be selected with the -z option.
SECURITY-CONTEXT is the SELinux security context.  This column must be selected with the -Z option.  Note that the -Z option is inhibited when SELinux is disabled in the running Linux kernel.
PPID       is the Parent Process IDentification number of the process. It is only displayed when the -R option has been specified.
PGID       is the process group IDentification number associated with the process.  It is only displayed when the -g option has been specified.
USER       is the user ID number or login name of the user to whom the process belongs, usually the same as reported by ps(1). However, on Linux USER is the user ID number or login that owns the directory in /proc where lsof finds information about the process.  Usually that is the same value reported by ps(1), but may differ when the process has changed its effective user ID.  (See the -l option description for information on when a user ID number or login name is displayed.)
FD         is the File Descriptor number of the file or:
cwd  current working directory; Lnn  library references (AIX); 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;
FD is 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 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:
N for a Solaris NFS lock of unknown type; 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; x for an SCO OpenServer Xenix lock on part      of the file; X for an SCO OpenServer Xenix lock on the entire file; space if there is no lock.
See the LOCKS section for more information on the lock information character.
The FD column contents constitutes a single field for parsing in post-processing scripts.
TYPE       is the type of the node associated with the file - e.g., GDIR, GREG, VDIR, VREG, etc.
or ``IPv4'' for an IPv4 socket;
or ``IPv6'' for an open IPv6 network file - even if its address is IPv4, mapped in an IPv6 address;
or ``ax25'' for a Linux AX.25 socket;
or ``inet'' for an Internet domain socket;
or ``lla'' for a HP-UX link level access file;
or ``rte'' for an AF_ROUTE socket;
or ``sock'' for a socket of unknown domain;
or ``unix'' for a UNIX domain socket;
or ``x.25'' for an HP-UX x.25 socket;
or ``BLK'' for a block special file;
or ``CHR'' for a character special file;
or ``DEL'' for a Linux map file that has been deleted;
or ``DIR'' for a directory;
or ``DOOR'' for a VDOOR file;
or ``FIFO'' for a FIFO special file;
or ``KQUEUE'' for a BSD style kernel event queue file;
or ``LINK'' for a symbolic link file;
or ``MPB'' for a multiplexed block file;
or ``MPC'' for a multiplexed character file;
or ``NOFD'' for a Linux /proc/<PID>/fd directory that can't be opened -- the directory path appears in the NAME column, followed by an error message;
or ``PAS'' for a /proc/as file;
or ``PAXV'' for a /proc/auxv file;
or ``PCRE'' for a /proc/cred file;
or ``PCTL'' for a /proc control file;
or ``PCUR'' for the current /proc process;
or ``PCWD'' for a /proc current working directory;
or ``PDIR'' for a /proc directory;
or ``PETY'' for a /proc executable type (etype);
or ``PFD'' for a /proc file descriptor;
or ``PFDR'' for a /proc file descriptor directory;
or ``PFIL'' for an executable /proc file;
or ``PFPR'' for a /proc FP register set;
or ``PGD'' for a /proc/pagedata file;
or ``PGID'' for a /proc group notifier file;
or ``PIPE'' for pipes;
or ``PLC'' for a /proc/lwpctl file;
or ``PLDR'' for a /proc/lpw directory;
or ``PLDT'' for a /proc/ldt file;
or ``PLPI'' for a /proc/lpsinfo file;
or ``PLST'' for a /proc/lstatus file;
or ``PLU'' for a /proc/lusage file;
or ``PLWG'' for a /proc/gwindows file;
or ``PLWI'' for a /proc/lwpsinfo file;
or ``PLWS'' for a /proc/lwpstatus file;
or ``PLWU'' for a /proc/lwpusage file;
or ``PLWX'' for a /proc/xregs file;
or ``PMAP'' for a /proc map file (map);
or ``PMEM'' for a /proc memory image file;
or ``PNTF'' for a /proc process notifier file;
or ``POBJ'' for a /proc/object file;
or ``PODR'' for a /proc/object directory;
or ``POLP'' for an old format /proc light weight process file;
or ``POPF'' for an old format /proc PID file;
or ``POPG'' for an old format /proc page data file;
or ``PORT'' for a SYSV named pipe;
or ``PREG'' for a /proc register file;
or ``PRMP'' for a /proc/rmap file;
or ``PRTD'' for a /proc root directory;
or ``PSGA'' for a /proc/sigact file;
or ``PSIN'' for a /proc/psinfo file;
or ``PSTA'' for a /proc status file;
or ``PSXMQ'' for a POSIX message queue file;
or ``PSXSEM'' for a POSIX semaphore file;
or ``PSXSHM'' for a POSIX shared memory file;
or ``PTS'' for a /dev/pts file;
or ``PUSG'' for a /proc/usage file;
or ``PW'' for a /proc/watch file;
or ``PXMP'' for a /proc/xmap file;
or ``REG'' for a regular file;
or ``SMT'' for a shared memory transport file;
or ``STSO'' for a stream socket;
or ``UNNM'' for an unnamed type file;
or ``XNAM'' for an OpenServer Xenix special file of unknown type;
or ``XSEM'' for an OpenServer Xenix semaphore file;
or ``XSD'' for an OpenServer Xenix shared data file;
or the four type number octets if the corresponding name isn't known.
FILE-ADDR  contains the kernel file structure address when f has been specified to +f;
FCT        contains the file reference count from the kernel file structure when c has been specified to +f;
FILE-FLAG  when g or G has been specified to +f, this field contains the contents of the f_flag[s] member of the kernel file structure and the kernel's per-process open file flags (if available); `G' causes them to be displayed in hexadecimal; `g', as short-hand names; two lists may be displayed with entries separated by commas, the lists separated by a semicolon (`;'); the first list may contain short-hand names for f_flag[s] values from the following table:
AIO       asynchronous I/O (e.g., FAIO) AP        append ASYN      asynchronous I/O (e.g., FASYNC) BAS       block, test, and set in use BKIU      block if in use BL        use block offsets BSK       block seek CA        copy avoid CIO       concurrent I/O CLON      clone CLRD      CL read CR        create DF        defer DFI       defer IND DFLU      data flush DIR       direct DLY       delay DOCL      do clone DSYN      data-only integrity DTY       must be a directory EVO       event only EX        open for exec EXCL      exclusive open FSYN      synchronous writes GCDF      defer during unp_gc() (AIX) GCMK      mark during unp_gc() (AIX) GTTY      accessed via /dev/tty HUP       HUP in progress KERN      kernel KIOC      kernel-issued ioctl LCK       has lock LG        large file MBLK      stream message block MK        mark MNT       mount MSYN      multiplex synchronization NATM      don't update atime NB        non-blocking I/O NBDR      no BDRM check NBIO      SYSV non-blocking I/O NBF       n-buffering in effect NC        no cache ND        no delay NDSY      no data synchronization NET       network NFLK      don't follow links NMFS      NM file system NOTO      disable background stop NSH       no share NTTY      no controlling TTY OLRM      OLR mirror PAIO      POSIX asynchronous I/O PATH      path PP        POSIX pipe R         read RC        file and record locking cache REV       revoked RSH       shared read RSYN      read synchronization RW        read and write access SL        shared lock SNAP      cooked snapshot SOCK      socket SQSH      Sequent shared set on open SQSV      Sequent SVM set on open SQR       Sequent set repair on open SQS1      Sequent full shared open SQS2      Sequent partial shared open STPI      stop I/O SWR       synchronous read SYN       file integrity while writing TCPM      avoid TCP collision TMPF      temporary file TR        truncate W         write WKUP      parallel I/O synchronization WTG       parallel I/O synchronization VH        vhangup pending VTXT      virtual text XL        exclusive lock
this list of names was derived from F* #define's in dialect header files <fcntl.h>, <linux</fs.h>, <sys/fcntl.c>, <sys/fcntlcom.h>, and <sys/file.h>; see the lsof.h header file for a list showing the correspondence between the above short-hand names and the header file definitions;
the second list (after the semicolon) may contain short-hand names for kernel per-process open file flags from this table:
ALLC      allocated BR        the file has been read BHUP      activity stopped by SIGHUP BW        the file has been written CLSG      closing CX        close-on-exec (see fcntl(F_SETFD)) LCK       lock was applied MP        memory-mapped OPIP      open pending - in progress RSVW      reserved wait SHMT      UF_FSHMAT set (AIX) USE       in use (multi-threaded)
NODE-ID    (or INODE-ADDR for some dialects) contains a unique identifier for the file node (usually the kernel vnode or inode address, but also occasionally a concatenation of device and node number) when n has been specified to +f;
DEVICE     contains the device numbers, separated by commas, for a character special, block special, regular, directory or NFS file;
or ``memory'' for a memory file system node under Tru64 UNIX;
or the address of the private data area of a Solaris socket stream;
or a kernel reference address that identifies the file (The kernel reference address may be used for FIFO's, for example.);
or the base address or device name of a Linux AX.25 socket device.
Usually only the lower thirty two bits of Tru64 UNIX kernel addresses are displayed.
SIZE, SIZE/OFF, or OFFSET is the size of the file or the file offset in bytes.  A value is displayed in this column only if it is available.  Lsof displays whatever value - size or offset - is appropriate for the type of the file and the version of lsof.
On some UNIX dialects lsof can't obtain accurate or consistent file offset information from its kernel data sources, sometimes just for particular kinds of files (e.g., socket files.)  In other cases, files don't have true sizes - e.g., sockets, FIFOs, pipes - so lsof displays for their sizes the content amounts it finds in their kernel buffer descriptors (e.g., socket buffer size counts or TCP/IP window sizes.) Consult the lsof FAQ (The FAQ section gives its location.) for more information.
The file size is displayed in decimal; the offset is normally displayed in decimal with a leading ``0t'' if it contains 8 digits or less; in hexadecimal with a leading ``0x'' if it is longer than 8 digits.  (Consult the -o o option description for information on when 8 might default to some other value.)
Thus the leading ``0t'' and ``0x'' identify an offset when the column may contain both a size and an offset (i.e., its title is SIZE/OFF).
If the -o option is specified, lsof always displays the file offset (or nothing if no offset is available) and labels the column OFFSET.  The offset always begins with ``0t'' or ``0x'' as described above.
The lsof user can control the switch from ``0t'' to ``0x'' with the -o o option.  Consult its description for more information.
If the -s option is specified, lsof always displays the file size (or nothing if no size is available) and labels the column SIZE.  The -o and -s options are mutually exclusive; they can't both be specified.
For files that don't have a fixed size - e.g., don't reside on a disk device - lsof will display appropriate information about the current size or position of the file if it is available in the kernel structures that define the file.
NLINK      contains the file link count when +L has been specified;
NODE       is the node number of a local file;
or the inode number of an NFS file in the server host;
or the Internet protocol type - e.g, ``TCP'';
or ``STR'' for a stream;
or ``CCITT'' for an HP-UX x.25 socket;
or the IRQ or inode number of a Linux AX.25 socket device.
NAME       is the name of the mount point and file system on which the file resides;
or the name of a file specified in the names option (after any symbolic links have been resolved);
or the name of a character special or block special device;
or the local and remote Internet addresses of a network file; the local host name or IP number is followed by a colon (':'), the port, ``->'', and the two-part remote address; IP addresses may be reported as numbers or names, depending on the +|-M, -n, and -P options; colon-separated IPv6 numbers are enclosed in square brackets; IPv4 INADDR_ANY and IPv6 IN6_IS_ADDR_UNSPECIFIED addresses, and zero port numbers are represented by an asterisk ('*'); a UDP destination address may be followed by the amount of time elapsed since the last packet was sent to the destination; TCP, UDP and UDPLITE remote addresses may be followed by TCP/TPI information in parentheses - state (e.g., ``(ESTABLISHED)'', ``(Unbound)''), queue sizes, and window sizes (not all dialects) - in a fashion similar to what netstat(1) reports; see the -T option description or the description of the TCP/TPI field in OUTPUT FOR OTHER PROGRAMS for more information on state, queue size, and window size;
or the address or name of a UNIX domain socket, possibly including a stream clone device name, a file system object's path name, local and foreign kernel addresses, socket pair information, and a bound vnode address;
or the local and remote mount point names of an NFS file;
or ``STR'', followed by the stream name;
or a stream character device name, followed by ``->'' and the stream name or a list of stream module names, separated by ``->'';
or ``STR:'' followed by the SCO OpenServer stream device and module names, separated by ``->'';
or system directory name, `` -- '', and as many components of the path name as lsof can find in the kernel's name cache for selected dialects (See the KERNEL NAME CACHE section for more information.);
or ``PIPE->'', followed by a Solaris kernel pipe destination address;
or ``COMMON:'', followed by the vnode device information structure's device name, for a Solaris common vnode;
or the address family, followed by a slash (`/'), followed by fourteen comma-separated bytes of a non-Internet raw socket address;
or the HP-UX x.25 local address, followed by the virtual connection number (if any), followed by the remote address (if any);
or ``(dead)'' for disassociated Tru64 UNIX files - typically terminal files that have been flagged with the TIOCNOTTY ioctl and closed by daemons;
or ``rd=<offset>'' and ``wr=<offset>'' for the values of the read and write offsets of a FIFO;
or ``clone n:/dev/event'' for SCO OpenServer file clones of the /dev/event device, where n is the minor device number of the file;
or ``(socketpair: n)'' for a Solaris 2.6, 8, 9  or 10 UNIX domain socket, created by the socketpair(3N) network function;
or ``no PCB'' for socket files that do not have a protocol block associated with them, optionally followed by ``, CANTSENDMORE'' if sending on the socket has been disabled, or ``, CANTRCVMORE'' if receiving on the socket has been disabled (e.g., by the shutdown(2) function);
or the local and remote addresses of a Linux IPX socket file in the form <net>:[<node>:]<port>, followed in parentheses by the transmit and receive queue sizes, and the connection state;
or ``dgram'' or ``stream'' for the type UnixWare 7.1.1 and above in-kernel UNIX domain sockets, followed by a colon (':') and the local path name when available, followed by ``->'' and the remote path name or kernel socket address in hexadecimal when available;
or the association value, association index, endpoint value, local address, local port, remote address and remote port for Linux SCTP sockets;
or ``protocol: '' followed by the Linux socket's protocol attribute.
For dialects that support a ``namefs'' file system, allowing one file to be attached to another with fattach(3C), lsof will add ``(FA:<address1><direction><address2>)'' to the NAME column.  <address1> and <address2> are hexadecimal vnode addresses.  <direction> will be ``<-'' if <address2> has been fattach'ed to this vnode whose address is <address1>; and ``->'' if <address1>, the vnode address of this vnode, has been fattach'ed to <address2>.  <address1> may be omitted if it already appears in the DEVICE column.
Lsof may add two parenthetical notes to the NAME column for open Solaris 10 files: ``(?)'' if lsof considers the path name of questionable accuracy; and ``(deleted)'' if the -X option has been specified and lsof detects the open file's path name has been deleted.  Consult the lsof FAQ (The FAQ section gives its location.)  for more information on these NAME column additions.
Lsof can't adequately report the wide variety of UNIX dialect file locks in a single character.  What it reports in a single character is a compromise between the information it finds in the kernel and the limitations of the reporting format.
Moreover, when a process holds several byte level locks on a file, lsof only reports the status of the first lock it encounters.  If it is a byte level lock, then the lock character will be reported in lower case - i.e., `r', `w', or `x' - rather than the upper case equivalent reported for a full file lock.
Generally lsof can only report on locks held by local processes on local files.  When a local process sets a lock on a remotely mounted (e.g., NFS) file, the remote server host usually records the lock state.  One exception is Solaris - at some patch levels of 2.3, and in all versions above 2.4, the Solaris kernel records information on remote locks in local structures.
Lsof has trouble reporting locks for some UNIX dialects.  Consult the BUGS section of this manual page or the lsof FAQ (The FAQ section gives its location.)  for more information.
When the -F option is specified, lsof produces output that is suitable for processing by another program - e.g, an awk or Perl script, or a C program.
Each unit of information is output in a field that is identified with a leading character and terminated by a NL (012) (or a NUL (000) if the 0 (zero) field identifier character is specified.)  The data of the field follows immediately after the field identification character and extends to the field terminator.
It is possible to think of field output as process and file sets.  A process set begins with a field whose identifier is `p' (for process IDentifier (PID)).  It extends to the beginning of the next PID field or the beginning of the first file set of the process, whichever comes first.  Included in the process set are fields that identify the command, the process group IDentification (PGID) number, the task (thread) ID (TID), and the user ID (UID) number or login name.
A file set begins with a field whose identifier is `f' (for file descriptor).  It is followed by lines that describe the file's access mode, lock state, type, device, size, offset, inode, protocol, name and stream module names.  It extends to the beginning of the next file or process set, whichever comes first.
When the NUL (000) field terminator has been selected with the 0 (zero) field identifier character, lsof ends each process and file set with a NL (012) character.
Lsof always produces one field, the PID (`p') field.  In repeat mode, the marker (`m') is also produced.  All other fields may be declared optionally in the field identifier character list that follows the -F option.  When a field selection character identifies an item lsof does not normally list - e.g., PPID, selected with -R - specification of the field character - e.g., ``-FR'' - also selects the listing of the item.
Lsof version from 4.88 to 4.93.2 always produced one more field, the file descriptor (`f') field. However, lsof in this version doesn't produce it. This change is for supporting the use case that a user needs only the PID field, and doesn't need the file descriptor field. Specify `f' explicitly if you need the field.
It is entirely possible to select a set of fields that cannot easily be parsed - e.g., if the field descriptor field is not selected, it may be difficult to identify file sets.  To help you avoid this difficulty, lsof supports the -F option; it selects the output of all fields with NL terminators (the -F0 option pair selects the output of all fields with NUL terminators).  For compatibility reasons neither -F nor -F0 select the raw device field.
These are the fields that lsof will produce.  The single character listed first is the field identifier.
a    file access mode c    process command name (all characters from proc or user structure) C    file structure share count d    file's device character code D    file's major/minor device number (0x<hexadecimal>) f    file descriptor F    file structure address (0x<hexadecimal>) G    file flaGs (0x<hexadecimal>; names if +fg follows) g    process group ID i    file's inode number K    tasK ID k    link count l    file's lock status L    process login name m    marker between repeated output (always selected in repeat mode) M    the task comMand name n    file name, comment, Internet address N    node identifier (ox<hexadecimal> o    file's offset (0t<decimal> or 0x<hexadecimal>, see -o o) p    process ID (always selected) P    protocol name r    raw device number (0x<hexadecimal>) R    parent process ID s    file's size (decimal) S    file's stream identification t    file's type T    TCP/TPI information, identified by prefixes (the `=' is part of the prefix): QR=<read queue size> QS=<send queue size> SO=<socket options and values> (not all dialects) SS=<socket states> (not all dialects) ST=<connection state> TF=<TCP flags and values> (not all dialects) WR=<window read size>  (not all dialects) WW=<window write size>  (not all dialects) (TCP/TPI information isn't reported for all supported UNIX dialects. The -h or -? help output for the -T option will show what TCP/TPI reporting can be requested.) u    process user ID z    Solaris 10 and higher zone name Z    SELinux security context (inhibited when SELinux is disabled) 0    use NUL field terminator character in place of NL 1-9  dialect-specific field identifiers (The output of -F? identifies the information to be found in dialect-specific fields.)
You can get on-line help information on these characters and their descriptions by specifying the -F?  option pair.  (Escape the `?' character as your shell requires.)  Additional information on field content can be found in the OUTPUT section.
As an example, ``-F pcfn'' will select the process ID (`p'), command name (`c'), file descriptor (`f') and file name (`n') fields with an NL field terminator character; ``-F pcfn0'' selects the same output with a NUL (000) field terminator character.
Lsof doesn't produce all fields for every process or file set, only those that are available.  Some fields are mutually exclusive: file device characters and file major/minor device numbers; file inode number and protocol name; file name and stream identification; file size and offset. One or the other member of these mutually exclusive sets will appear in field output, but not both.
Normally lsof ends each field with a NL (012) character.  The 0 (zero) field identifier character may be specified to change the field terminator character to a NUL (000).  A NUL terminator may be easier to process with xargs (1), for example, or with programs whose quoting mechanisms may not easily cope with the range of characters in the field output.  When the NUL field terminator is in use, lsof ends each process and file set with a NL (012).
Three aids to producing programs that can process lsof field output are included in the lsof distribution.  The first is a C header file, lsof_fields.h, that contains symbols for the field identification characters, indexes for storing them in a table, and explanation strings that may be compiled into programs.  Lsof uses this header file.
The second aid is a set of sample scripts that process field output, written in awk, Perl 4, and Perl 5.  They're located in the scripts subdirectory of the lsof distribution.
The third aid is the C library used for the lsof test suite.  The test suite is written in C and uses field output to validate the correct operation of lsof.  The library can be found in the tests/LTlib.c file of the lsof distribution.  The library uses the first aid, the lsof_fields.h header file.
Lsof can be blocked by some kernel functions that it uses - lstat(2), readlink(2), and stat(2).  These functions are stalled in the kernel, for example, when the hosts where mounted NFS file systems reside become inaccessible.
Lsof attempts to break these blocks with timers and child processes, but the techniques are not wholly reliable.  When lsof does manage to break a block, it will report the break with an error message.  The messages may be suppressed with the -t and -w options.
The default timeout value may be displayed with the -h or -?  option, and it may be changed with the -S [t] option.  The minimum for t is two seconds, but you should avoid small values, since slow system responsiveness can cause short timeouts to expire unexpectedly and perhaps stop lsof before it can produce any output.
When lsof has to break a block during its access of mounted file system information, it normally continues, although with less information available to display about open files.
Lsof can also be directed to avoid the protection of timers and child processes when using the kernel functions that might block by specifying the -O option.  While this will allow lsof to start up with less overhead, it exposes lsof completely to the kernel situations that might block it.  Use this option cautiously.
You can use the -b option to tell lsof to avoid using kernel functions that would block.  Some cautions apply.
First, using this option usually requires that your system supply alternate device numbers in place of the device numbers that lsof would normally obtain with the lstat(2) and stat(2) kernel functions.  See the ALTERNATE DEVICE NUMBERS section for more information on alternate device numbers.
Second, you can't specify names for lsof to locate unless they're file system names.  This is because lsof needs to know the device and inode numbers of files listed with names in the lsof options, and the -b option prevents lsof from obtaining them.  Moreover, since lsof only has device numbers for the file systems that have alternates, its ability to locate files on file systems depends completely on the availability and accuracy of the alternates.  If no alternates are available, or if they're incorrect, lsof won't be able to locate files on the named file systems.
Third, if the names of your file system directories that lsof obtains from your system's mount table are symbolic links, lsof won't be able to resolve the links.  This is because the -b option causes lsof to avoid the kernel readlink(2) function it uses to resolve symbolic links.
Finally, using the -b option causes lsof to issue warning messages when it needs to use the kernel functions that the -b option directs it to avoid.  You can suppress these messages by specifying the -w option, but if you do, you won't see the alternate device numbers reported in the warning messages.
On some dialects, when lsof has to break a block because it can't get information about a mounted file system via the lstat(2) and stat(2) kernel functions, or because you specified the -b option, lsof can obtain some of the information it needs - the device number and possibly the file system type - from the system mount table.  When that is possible, lsof will report the device number it obtained.  (You can suppress the report by specifying the -w option.)
You can assist this process if your mount table is supported with an /etc/mtab or /etc/mnttab file that contains an options field by adding a ``dev=xxxx'' field for mount points that do not have one in their options strings.  Note: you must be able to edit the file - i.e., some mount tables like recent Solaris /etc/mnttab or Linux /proc/mounts are read-only and can't be modified.
You may also be able to supply device numbers using the +m and +m m options, provided they are supported by your dialect.  Check the output of lsof's -h or -?  options to see if the +m and +m m options are available.
The ``xxxx'' portion of the field is the hexadecimal value of the file system's device number.  (Consult the st_dev field of the output of the lstat(2) and stat(2) functions for the appropriate values for your file systems.)  Here's an example from a Sun Solaris 2.6 /etc/mnttab for a file system remotely mounted via NFS:
nfs  ignore,noquota,dev=2a40001
There's an advantage to having ``dev=xxxx'' entries in your mount table file, especially for file systems that are mounted from remote NFS servers.  When a remote server crashes and you want to identify its users by running lsof on one of its clients, lsof probably won't be able to get output from the lstat(2) and stat(2) functions for the file system.  If it can obtain the file system's device number from the mount table, it will be able to display the files open on the crashed NFS server.
Some dialects that do not use an ASCII /etc/mtab or /etc/mnttab file for the mount table may still provide an alternative device number in their internal mount tables.  This includes AIX, Apple Darwin, FreeBSD, NetBSD, OpenBSD, and Tru64 UNIX.  Lsof knows how to obtain the alternative device number for these dialects and uses it when its attempt to lstat(2) or stat(2) the file system is blocked.