proc_pid_fd(5) File Formats Manual proc_pid_fd(5) /proc/pid/fd/ - file descriptors /proc/pid/fd/ , , , . , 0 -- , 1 -- , 2 -- .. , -- inode. readlink(2) : type:[inode] , socket:[2248868] -- inode 2248868. inode /proc/net/. (, , bpf(2), epoll_create(2), eventfd(2), inotify_init(2), perf_event_open(2), signalfd(2), timerfd_create(2) userfaultfd(2)), anon_inode:- ( ) - . , epoll anon_inode:[eventpoll]. , , ( pthread_exit(3)). , , , , , , , , , , , /proc/pid/fd, . , -i , , -o , , : $ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 . /proc/self/fd/N -- , /dev/fd/N UNIX . , MAKEDEV Linux /dev/fd /proc/self/fd. /dev/stdin, /dev/stdout /dev/stderr, 0, 1 2 /proc/self/fd. , : $ foobar -i /dev/stdin -o /dev/stdout ... (readlink(2)) ptrace PTRACE_MODE_READ_FSCREDS; ptrace(2). , , ( , ), - /proc/pid/fd . , : $ echo test | sudo -u nobody cat test $ echo test | sudo -u nobody cat /proc/self/fd/0 cat: /proc/self/fd/0: Permission denied 0 , , nobody, cat , - 0. proc(5) () Alexey, Azamat Hackimov , kogamatranslator49 , Darima Kogan , Max Is , Yuri Kozlov , Kirill Rekhov ; GNU (GNU General Public License - GPL, 3 ) , - . - , , () () () <>. Linux 6.9.1 2 2024 . proc_pid_fd(5)