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Re: writing to a named pipe (FIFO) fails




On 22/11/2006, at 12:32 AM, Cameron Hayne wrote:

I am trying (but failing) to write to a FIFO or named pipe (http://en.wikipedia.org/wiki/Named_pipe) from AppleScript.

from your description it looks like you are succeeding.


Here's an example script (the named pipe at "/Users/myusername/mystuff/myfifo" is set up previously in a Terminal window):
----------------------------------------------------------------------- -----
set fifo to "/Users/myusername/mystuff/myfifo"
do shell script "echo AAA > " & fifo

This works, but it's the end of the shell. Your named pipe is now a file on disk like any other.



set macFifo to POSIX file fifo

try
	write "BBB" to macFifo
on error errString number errNum
	display alert errString & " (" & errNum & ")"
end try


Works (I'm running 10.3.9)


try
	set fd to open for access macFifo with write permission
	write "CCC" to fd
	close access fd
on error errString number errNum
	display alert errString & " (" & errNum & ")"
end try

Works


----------------------------------------------------------------------- -----
The 'do shell script' works fine and the "AAA" gets transmitted to the named pipe.


When you read myfifo at that point does it contain "AAA" ? If so, you succeeded.


But the two attempts ("BBB" & "CCC") to write to the named pipe using 'write' both fail with error -36 which is "ioErr (-36): I/O error (bummers)".
Note that if I change the above example to refer to a regular file, it all works fine.

The way I understand it, it is a regular file. The fact that you named a pipe to generate it doesn't make it different. Am I wrong?



Is there any way to write to a named pipe (FIFO) using 'write' in AppleScript?

All you are doing with a named pipe is dumping the output of a process into a file.


This is an applescript way of doing the same thing.

on timeStamp()
	return (current date) as string
end timeStamp

set fPath to ("" & (path to desktop))
set fname to "ascr.log"
set namedPipe to open for access file (fPath & fname) with write permission


repeat 10 times
	write timeStamp() & return to namedPipe
end repeat

close access namedPipe
# now the results are in the file instead of the ether :-)
read file (fPath & fname)


I want to avoid the use of 'do shell script' for reasons of performance (each 'do shell script' seems to take about 0.1 second and in my AppleScript I will be doing thousands of writes to the named pipe).

In that case, tell us what you are trying to achieve.


malcolm

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 >writing to a named pipe (FIFO) fails (From: Cameron Hayne <email@hidden>)



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