04-14-2004
Struggling with mkfifo
Gurus,
I did my research (on google, this site and my local library) but I am *still* lost. I am trying to teach myself about `named pipes` playing around with MKFIFO (Why not?).
(1) It seems MKNOD is reserved to ROOT whereas MKFIFO is accessible to all users. Am I correct? If the answer is `yes,` can someone explain why? Based on what I read, both commands seem to produce the same results...
(2) I can create a fifo on a empty file e.g. `mkfifo empty_file` but when I attempt to edit it in VI (as myself or another userid), my editor never comes up. Is it because the blocking nature of the named pipe I created?
(3) It seems that when a process (here, VI) reads from a named pipe that has no data in it (here, `empty_file), the reading process is blocked. Fine. So, how do I write to it??
(4) Why can't I create a fifo out of an already existing file? Is it possible if I specify the correct mode e.g. `mkfifo already_existing_file +RW...`?
(5) Where can I find more *detailed* info about this topic?
Thanks in advance to all for sharing your knowledge. Al.
PS: I am on HP-UX B.11.00 U 9000/800.
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MKFIFO(1) User Commands MKFIFO(1)
NAME
mkfifo - make FIFOs (named pipes)
SYNOPSIS
mkfifo [OPTION]... NAME...
DESCRIPTION
Create named pipes (FIFOs) with the given NAMEs.
Mandatory arguments to long options are mandatory for short options too.
-m, --mode=MODE
set file permission bits to MODE, not a=rw - umask
-Z set the SELinux security context to default type
--context[=CTX]
like -Z, or if CTX is specified then set the SELinux or SMACK security context to CTX
--help display this help and exit
--version
output version information and exit
AUTHOR
Written by David MacKenzie.
REPORTING BUGS
GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Report mkfifo translation bugs to <http://translationproject.org/team/>
COPYRIGHT
Copyright (C) 2017 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
mkfifo(3)
Full documentation at: <http://www.gnu.org/software/coreutils/mkfifo>
or available locally via: info '(coreutils) mkfifo invocation'
GNU coreutils 8.28 January 2018 MKFIFO(1)