# proc_pid_fdinfo - information about file descriptors - man(5) - [phpMan] [_proc_pid_fdinfo_(5)](https://www.chedong.com/phpMan.php/man/procpidfdinfo/5/markdown) File Formats Manual [_proc_pid_fdinfo_(5)](https://www.chedong.com/phpMan.php/man/procpidfdinfo/5/markdown) ## NAME /proc/pid/fdinfo/ - information about file descriptors ## DESCRIPTION _/proc/_pid_/fdinfo/_ (since Linux 2.6.22) This is a subdirectory containing one entry for each file which the process has open, named by its file descriptor. The files in this directory are readable only by the owner of the process. The contents of each file can be read to obtain information about the corresponding file descriptor. The content depends on the type of file re‐ ferred to by the corresponding file descriptor. For regular files and directories, we see something like: $ **cat /proc/12015/fdinfo/4** pos: 1000 flags: 01002002 mnt_id: 21 The fields are as follows: _pos_ This is a decimal number showing the file offset. _flags_ This is an octal number that displays the file access mode and file status flags (see [**open**(2)](https://www.chedong.com/phpMan.php/man/open/2/markdown)). If the close-on-exec file descriptor flag is set, then _flags_ will also include the value **O_CLOEXEC**. Before Linux 3.1, this field incorrectly displayed the setting of **O_CLOEXEC **at the time the file was opened, rather than the current setting of the close-on- exec flag. _mnt_id_ This field, present since Linux 3.15, is the ID of the mount containing this file. See the description of _/proc/_pid_/mountinfo_. For eventfd file descriptors (see [**eventfd**(2)](https://www.chedong.com/phpMan.php/man/eventfd/2/markdown)), we see (since Linux 3.8) the following fields: pos: 0 flags: 02 mnt_id: 10 eventfd-count: 40 _eventfd-count_ is the current value of the eventfd counter, in hexadecimal. For epoll file descriptors (see [**epoll**(7)](https://www.chedong.com/phpMan.php/man/epoll/7/markdown)), we see (since Linux 3.8) the following fields: pos: 0 flags: 02 mnt_id: 10 tfd: 9 events: 19 data: 74253d2500000009 tfd: 7 events: 19 data: 74253d2500000007 Each of the lines beginning _tfd_ describes one of the file descriptors being monitored via the epoll file descriptor (see [**epoll_ctl**(2)](https://www.chedong.com/phpMan.php/man/epollctl/2/markdown) for some details). The _tfd_ field is the number of the file descriptor. The _events_ field is a hexadecimal mask of the events being monitored for this file descriptor. The _data_ field is the data value as‐ sociated with this file descriptor. For signalfd file descriptors (see [**signalfd**(2)](https://www.chedong.com/phpMan.php/man/signalfd/2/markdown)), we see (since Linux 3.8) the follow‐ ing fields: pos: 0 flags: 02 mnt_id: 10 sigmask: 0000000000000006 _sigmask_ is the hexadecimal mask of signals that are accepted via this signalfd file descriptor. (In this example, bits 2 and 3 are set, corresponding to the signals **SIG‐** **INT **and **SIGQUIT**; see [**signal**(7)](https://www.chedong.com/phpMan.php/man/signal/7/markdown).) For inotify file descriptors (see [**inotify**(7)](https://www.chedong.com/phpMan.php/man/inotify/7/markdown)), we see (since Linux 3.8) the following fields: pos: 0 flags: 00 mnt_id: 11 inotify wd:2 ino:7ef82a sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:2af87e00220ffd73 inotify wd:1 ino:192627 sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:27261900802dfd73 Each of the lines beginning with "inotify" displays information about one file or di‐ rectory that is being monitored. The fields in this line are as follows: _wd_ A watch descriptor number (in decimal). _ino_ The inode number of the target file (in hexadecimal). _sdev_ The ID of the device where the target file resides (in hexadecimal). _mask_ The mask of events being monitored for the target file (in hexadecimal). If the kernel was built with exportfs support, the path to the target file is exposed as a file handle, via three hexadecimal fields: _fhandle-bytes_, _fhandle-type_, and _f_handle_. For fanotify file descriptors (see [**fanotify**(7)](https://www.chedong.com/phpMan.php/man/fanotify/7/markdown)), we see (since Linux 3.8) the follow‐ ing fields: pos: 0 flags: 02 mnt_id: 11 fanotify flags:0 event-flags:88002 fanotify ino:19264f sdev:800001 mflags:0 mask:1 ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:4f261900a82dfd73 The fourth line displays information defined when the fanotify group was created via [**fanotify_init**(2)](https://www.chedong.com/phpMan.php/man/fanotifyinit/2/markdown): _flags_ The _flags_ argument given to [**fanotify_init**(2)](https://www.chedong.com/phpMan.php/man/fanotifyinit/2/markdown) (expressed in hexadecimal). _event-flags_ The _event_f_flags_ argument given to [**fanotify_init**(2)](https://www.chedong.com/phpMan.php/man/fanotifyinit/2/markdown) (expressed in hexadeci‐ mal). Each additional line shown in the file contains information about one of the marks in the fanotify group. Most of these fields are as for inotify, except: _mflags_ The flags associated with the mark (expressed in hexadecimal). _mask_ The events mask for this mark (expressed in hexadecimal). _ignored_mask_ The mask of events that are ignored for this mark (expressed in hexadecimal). For details on these fields, see [**fanotify_mark**(2)](https://www.chedong.com/phpMan.php/man/fanotifymark/2/markdown). For timerfd file descriptors (see [**timerfd**(2)](https://www.chedong.com/phpMan.php/man/timerfd/2/markdown)), we see (since Linux 3.17) the following fields: pos: 0 flags: 02004002 mnt_id: 13 clockid: 0 ticks: 0 settime flags: 03 it_value: (7695568592, 640020877) it_interval: (0, 0) _clockid_ This is the numeric value of the clock ID (corresponding to one of the **CLOCK_*** constants defined via __) that is used to mark the progress of the timer (in this example, 0 is **CLOCK_REALTIME**). _ticks_ This is the number of timer expirations that have occurred, (i.e., the value that [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown) on it would return). _settime_ _flags_ This field lists the flags with which the timerfd was last armed (see [**timerfd_settime**(2)](https://www.chedong.com/phpMan.php/man/timerfdsettime/2/markdown)), in octal (in this example, both **TFD_TIMER_ABSTIME **and **TFD_TIMER_CANCEL_ON_SET **are set). _it_value_ This field contains the amount of time until the timer will next expire, ex‐ pressed in seconds and nanoseconds. This is always expressed as a relative value, regardless of whether the timer was created using the **TFD_TIMER_ABSTIME** flag. _it_interval_ This field contains the interval of the timer, in seconds and nanoseconds. (The _it_value_ and _it_interval_ fields contain the values that [**timerfd_gettime**(2)](https://www.chedong.com/phpMan.php/man/timerfdgettime/2/markdown) on this file descriptor would return.) ## SEE ALSO [**proc**(5)](https://www.chedong.com/phpMan.php/man/proc/5/markdown) Linux man-pages 6.7 2023-08-15 [_proc_pid_fdinfo_(5)](https://www.chedong.com/phpMan.php/man/procpidfdinfo/5/markdown)