.\" Copyright (C) 1994, 1995, Daniel Quinlan .\" Copyright (C) 2002-2008, 2017, Michael Kerrisk .\" Copyright (C) 2023, Alejandro Colomar .\" .\" SPDX-License-Identifier: GPL-3.0-or-later .\" .TH proc_pid_fdinfo 5 2024-05-02 "Linux man-pages 6.9.1" .SH NAME /proc/pid/fdinfo/ \- information about file descriptors .SH DESCRIPTION .TP .IR /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 referred to by the corresponding file descriptor. .IP For regular files and directories, we see something like: .IP .in +4n .EX .RB "$" " cat /proc/12015/fdinfo/4" pos: 1000 flags: 01002002 mnt_id: 21 .EE .in .IP The fields are as follows: .RS .TP .I pos This is a decimal number showing the file offset. .TP .I flags This is an octal number that displays the file access mode and file status flags (see .BR open (2)). If the close-on-exec file descriptor flag is set, then .I flags will also include the value .BR O_CLOEXEC . .IP Before Linux 3.1, .\" commit 1117f72ea0217ba0cc19f05adbbd8b9a397f5ab7 this field incorrectly displayed the setting of .B O_CLOEXEC at the time the file was opened, rather than the current setting of the close-on-exec flag. .TP .I .I mnt_id This field, present since Linux 3.15, .\" commit 49d063cb353265c3af701bab215ac438ca7df36d is the ID of the mount containing this file. See the description of .IR /proc/ pid /mountinfo . .RE .IP For eventfd file descriptors (see .BR eventfd (2)), we see (since Linux 3.8) .\" commit cbac5542d48127b546a23d816380a7926eee1c25 the following fields: .IP .in +4n .EX pos: 0 flags: 02 mnt_id: 10 eventfd\-count: 40 .EE .in .IP .I eventfd\-count is the current value of the eventfd counter, in hexadecimal. .IP For epoll file descriptors (see .BR epoll (7)), we see (since Linux 3.8) .\" commit 138d22b58696c506799f8de759804083ff9effae the following fields: .IP .in +4n .EX pos: 0 flags: 02 mnt_id: 10 tfd: 9 events: 19 data: 74253d2500000009 tfd: 7 events: 19 data: 74253d2500000007 .EE .in .IP Each of the lines beginning .I tfd describes one of the file descriptors being monitored via the epoll file descriptor (see .BR epoll_ctl (2) for some details). The .I tfd field is the number of the file descriptor. The .I events field is a hexadecimal mask of the events being monitored for this file descriptor. The .I data field is the data value associated with this file descriptor. .IP For signalfd file descriptors (see .BR signalfd (2)), we see (since Linux 3.8) .\" commit 138d22b58696c506799f8de759804083ff9effae the following fields: .IP .in +4n .EX pos: 0 flags: 02 mnt_id: 10 sigmask: 0000000000000006 .EE .in .IP .I 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 .B SIGINT and .BR SIGQUIT ; see .BR signal (7).) .IP For inotify file descriptors (see .BR inotify (7)), we see (since Linux 3.8) the following fields: .IP .in +4n .EX 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 .EE .in .IP Each of the lines beginning with "inotify" displays information about one file or directory that is being monitored. The fields in this line are as follows: .RS .TP .I wd A watch descriptor number (in decimal). .TP .I ino The inode number of the target file (in hexadecimal). .TP .I sdev The ID of the device where the target file resides (in hexadecimal). .TP .I mask The mask of events being monitored for the target file (in hexadecimal). .RE .IP If the kernel was built with exportfs support, the path to the target file is exposed as a file handle, via three hexadecimal fields: .IR fhandle\-bytes , .IR fhandle\-type , and .IR f_handle . .IP For fanotify file descriptors (see .BR fanotify (7)), we see (since Linux 3.8) the following fields: .IP .in +4n .EX 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 .EE .in .IP The fourth line displays information defined when the fanotify group was created via .BR fanotify_init (2): .RS .TP .I flags The .I flags argument given to .BR fanotify_init (2) (expressed in hexadecimal). .TP .I event\-flags The .I event_f_flags argument given to .BR fanotify_init (2) (expressed in hexadecimal). .RE .IP 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: .RS .TP .I mflags The flags associated with the mark (expressed in hexadecimal). .TP .I mask The events mask for this mark (expressed in hexadecimal). .TP .I ignored_mask The mask of events that are ignored for this mark (expressed in hexadecimal). .RE .IP For details on these fields, see .BR fanotify_mark (2). .IP For timerfd file descriptors (see .BR timerfd (2)), we see (since Linux 3.17) .\" commit af9c4957cf212ad9cf0bee34c95cb11de5426e85 the following fields: .IP .in +4n .EX pos: 0 flags: 02004002 mnt_id: 13 clockid: 0 ticks: 0 settime flags: 03 it_value: (7695568592, 640020877) it_interval: (0, 0) .EE .in .RS .TP .I clockid This is the numeric value of the clock ID (corresponding to one of the .B CLOCK_* constants defined via .IR ) that is used to mark the progress of the timer (in this example, 0 is .BR CLOCK_REALTIME ). .TP .I ticks This is the number of timer expirations that have occurred, (i.e., the value that .BR read (2) on it would return). .TP .I settime flags This field lists the flags with which the timerfd was last armed (see .BR timerfd_settime (2)), in octal (in this example, both .B TFD_TIMER_ABSTIME and .B TFD_TIMER_CANCEL_ON_SET are set). .TP .I it_value This field contains the amount of time until the timer will next expire, expressed in seconds and nanoseconds. This is always expressed as a relative value, regardless of whether the timer was created using the .B TFD_TIMER_ABSTIME flag. .TP .I it_interval This field contains the interval of the timer, in seconds and nanoseconds. (The .I it_value and .I it_interval fields contain the values that .BR timerfd_gettime (2) on this file descriptor would return.) .RE .SH SEE ALSO .BR proc (5)