|
|
|
|
Bookmark this on Delicious
Share on Facebook
 Slashdot It!
Digg  posix_mkfifo
Create a fifo special file (a named pipe)
(PHP 4, PHP 5)
Code Examples / Notes » posix_mkfifotech
This is still not a solution: if I listen to commands on a pipe and output status on a separate pipe, PHP will block on both opens because something else has not already connected to this pipe. Because I can't do a low-level fcntl() to to set O_NONBLOCK or something like it, this always locks up and is really stupid. The only way I can get it to work is to spawn seperate subshells with system() and have them cat, or echo respectively and then the pipes work properly...usually? Its alot of trouble that we can't set the blocking on the open!!
uther pendragon
Note (quoted from `man 7 pipe` on debian linux): "On some systems (but not Linux), pipes are bidirectional: data can be transmitted in both directions between the pipe ends. According to POSIX.1-2001, pipes only need to be unidirectional. Portable applications should avoid reliance on bidirectional pipe semantics." Linux pipes are NOT bidirectional. Also, it appears to me that the use of fifo (named) pipes in php is pretty pointless as there appears to be NO way of determining whether opening (let alone reading) from it will block. stream_select SHOULD be able to accomplish this, unfortunatly you cannot get to this point because even trying to OPEN a pipe for read will block until there is a writer. I even tried to use popen("cat $name_of_pipe", 'r'), and even it blocked until it was opened for write by another process. enric jaen
A way to have a non-blocking pipe reader is to check first if the pipe exists. If so, then read from the pipe, otherwise do other stuff. This will work assuming that the writer creates the pipe, writes on it, and after that deletes the pipe. This is a blocking writer: <?php $pipe="/tmp/pipe"; $mode=0600; if(!file_exists($pipe)) { // create the pipe umask(0); posix_mkfifo($pipe,$mode); } $f = fopen($pipe,"w"); fwrite($f,"hello"); //block until there is a reader unlink($pipe); //delete pipe ?> And this is the non-blocking reader: <?php $pipe="/tmp/pipe"; if(!file_exists($pipe)) { echo "I am not blocked!"; } else { //block and read from the pipe $f = fopen($pipe,"r"); echo fread($f,10); } ?> |
Change Language
posix_access posix_ctermid posix_get_last_error posix_getcwd posix_getegid posix_geteuid posix_getgid posix_getgrgid posix_getgrnam posix_getgroups posix_getlogin posix_getpgid posix_getpgrp posix_getpid posix_getppid posix_getpwnam posix_getpwuid posix_getrlimit posix_getsid posix_getuid posix_initgroups posix_isatty posix_kill posix_mkfifo posix_mknod posix_setegid posix_seteuid posix_setgid posix_setpgid posix_setsid posix_setuid posix_strerror posix_times posix_ttyname posix_uname |
