Doubts on FIFO


 
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Old 06-06-2008
Doubts on FIFO

Hi ,
I m beginner for Unix and i want to use FIFO in my 2 Scripts . I want 1 script to read data from FIFO and other will write into FIFO.

Despite reading so many articles/posts i am still unable sunchronize my scripts.


My doubts are

1> Do We require both scripts as daemons to use FIFO ?
2> Below is my code ,pls modify it to make it work .


$ cat write
echo "name:" "Akshay" > /home/nbkpxj6/db.FIFO


$cat read
eventQueue=/home/user/db.FIFO

while : ; do


cat $eventQueue | while read name; do
echo $name
done

done

I m getting error " 0403-006 Execute permission denied."

I know above code can work for 2 separate terminals , but i want single terminal to run both scripts, write value and read value from FIFO.


Thanks in advance

Last edited by Akshay; 06-06-2008 at 09:04 AM..
 
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FIFO(7) 						     Linux Programmer's Manual							   FIFO(7)

NAME
fifo - first-in first-out special file, named pipe DESCRIPTION
A FIFO special file (a named pipe) is similar to a pipe, except that it is accessed as part of the file system. It can be opened by multi- ple processes for reading or writing. When processes are exchanging data via the FIFO, the kernel passes all data internally without writ- ing it to the file system. Thus, the FIFO special file has no contents on the file system; the file system entry merely serves as a refer- ence point so that processes can access the pipe using a name in the file system. The kernel maintains exactly one pipe object for each FIFO special file that is opened by at least one process. The FIFO must be opened on both ends (reading and writing) before data can be passed. Normally, opening the FIFO blocks until the other end is opened also. A process can open a FIFO in nonblocking mode. In this case, opening for read-only will succeed even if no-one has opened on the write side yet, opening for write-only will fail with ENXIO (no such device or address) unless the other end has already been opened. Under Linux, opening a FIFO for read and write will succeed both in blocking and nonblocking mode. POSIX leaves this behavior undefined. This can be used to open a FIFO for writing while there are no readers available. A process that uses both ends of the connection in order to communicate with itself should be very careful to avoid deadlocks. NOTES
When a process tries to write to a FIFO that is not opened for read on the other side, the process is sent a SIGPIPE signal. FIFO special files can be created by mkfifo(3), and are indicated by ls -l with the file type 'p'. SEE ALSO
mkfifo(1), open(2), pipe(2), sigaction(2), signal(2), socketpair(2), mkfifo(3), pipe(7) COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2008-12-03 FIFO(7)