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Diffstat (limited to 'man5/proc_pid_fd.5')
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diff --git a/man5/proc_pid_fd.5 b/man5/proc_pid_fd.5 deleted file mode 100644 index 2e3341ad8..000000000 --- a/man5/proc_pid_fd.5 +++ /dev/null @@ -1,161 +0,0 @@ -.\" Copyright (C) 1994, 1995, Daniel Quinlan <quinlan@yggdrasil.com> -.\" Copyright (C) 2002-2008, 2017, Michael Kerrisk <mtk.manpages@gmail.com> -.\" Copyright (C) 2023, Alejandro Colomar <alx@kernel.org> -.\" -.\" SPDX-License-Identifier: GPL-3.0-or-later -.\" -.TH proc_pid_fd 5 (date) "Linux man-pages (unreleased)" -.SH NAME -/proc/pid/fd/ \- file descriptors -.SH DESCRIPTION -.TP -.IR /proc/ pid /fd/ -This is a subdirectory containing one entry for each file which the -process has open, named by its file descriptor, and which is a -symbolic link to the actual file. -Thus, 0 is standard input, 1 standard output, 2 standard error, and so on. -.IP -For file descriptors for pipes and sockets, -the entries will be symbolic links whose content is the -file type with the inode. -A -.BR readlink (2) -call on this file returns a string in the format: -.IP -.in +4n -.EX -type:[inode] -.EE -.in -.IP -For example, -.I socket:[2248868] -will be a socket and its inode is 2248868. -For sockets, that inode can be used to find more information -in one of the files under -.IR /proc/net/ . -.IP -For file descriptors that have no corresponding inode -(e.g., file descriptors produced by -.BR bpf (2), -.BR epoll_create (2), -.BR eventfd (2), -.BR inotify_init (2), -.BR perf_event_open (2), -.BR signalfd (2), -.BR timerfd_create (2), -and -.BR userfaultfd (2)), -the entry will be a symbolic link with contents of the form -.IP -.in +4n -.EX -.RI anon_inode: file-type -.EE -.in -.IP -In many cases (but not all), the -.I file-type -is surrounded by square brackets. -.IP -For example, an epoll file descriptor will have a symbolic link -whose content is the string -.IR "anon_inode:[eventpoll]" . -.IP -.\"The following was still true as at kernel 2.6.13 -In a multithreaded process, the contents of this directory -are not available if the main thread has already terminated -(typically by calling -.BR pthread_exit (3)). -.IP -Programs that take a filename as a command-line argument, -but don't take input from standard input if no argument is supplied, -and programs that write to a file named as a command-line argument, -but don't send their output to standard output -if no argument is supplied, can nevertheless be made to use -standard input or standard output by using -.IR /proc/ pid /fd -files as command-line arguments. -For example, assuming that -.I \-i -is the flag designating an input file and -.I \-o -is the flag designating an output file: -.IP -.in +4n -.EX -.RB "$" " foobar \-i /proc/self/fd/0 \-o /proc/self/fd/1 ..." -.EE -.in -.IP -and you have a working filter. -.\" The following is not true in my tests (MTK): -.\" Note that this will not work for -.\" programs that seek on their files, as the files in the fd directory -.\" are not seekable. -.IP -.I /proc/self/fd/N -is approximately the same as -.I /dev/fd/N -in some UNIX and UNIX-like systems. -Most Linux MAKEDEV scripts symbolically link -.I /dev/fd -to -.IR /proc/self/fd , -in fact. -.IP -Most systems provide symbolic links -.IR /dev/stdin , -.IR /dev/stdout , -and -.IR /dev/stderr , -which respectively link to the files -.IR 0 , -.IR 1 , -and -.I 2 -in -.IR /proc/self/fd . -Thus the example command above could be written as: -.IP -.in +4n -.EX -.RB "$" " foobar \-i /dev/stdin \-o /dev/stdout ..." -.EE -.in -.IP -Permission to dereference or read -.RB ( readlink (2)) -the symbolic links in this directory is governed by a ptrace access mode -.B PTRACE_MODE_READ_FSCREDS -check; see -.BR ptrace (2). -.IP -Note that for file descriptors referring to inodes -(pipes and sockets, see above), -those inodes still have permission bits and ownership information -distinct from those of the -.IR /proc/ pid /fd -entry, -and that the owner may differ from the user and group IDs of the process. -An unprivileged process may lack permissions to open them, as in this example: -.IP -.in +4n -.EX -.RB "$" " echo test | sudo \-u nobody cat" -test -.RB "$" " echo test | sudo \-u nobody cat /proc/self/fd/0" -cat: /proc/self/fd/0: Permission denied -.EE -.in -.IP -File descriptor 0 refers to the pipe created by the shell -and owned by that shell's user, which is not -.IR nobody , -so -.B cat -does not have permission -to create a new file descriptor to read from that inode, -even though it can still read from its existing file descriptor 0. -.SH SEE ALSO -.BR proc (5) |