Re: writing to a named pipe (FIFO) fails
Re: writing to a named pipe (FIFO) fails
- Subject: Re: writing to a named pipe (FIFO) fails
- From: Malcolm Fitzgerald <email@hidden>
- Date: Wed, 22 Nov 2006 09:44:29 +1100
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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