showing console program output in GUI app
lazarus / 32-Linux

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Martin V · 2016-08-06 16:16

I have managed to redirect the output of a console program via named
pipes to my gui app and to print it to a memo field. On Windows, I
have used the Windows API functions:
- CreateNamedPipe
- ConnectNamedPipe
- I have run the console program synchronous via cmd.exe in an own
thread, by using >pipename behind the command line parameters
- after running the external program, a 300 ms sleep in the main
thread to get the time which is necessary to receive the rest of the
output
- DisConnectNamedPipe in the own thread
- in the main thead a loop with ReadFile which gets exited if ReadFile
results an error or 0 bytes read.

Meanwhile, the code works fine. But the named pipes concept seems to
be very different in Linux, I have not found any platform-independent
code in Freepascal/Lazarus for named pipes. There are only few API
calls. Which are the correct Unix API calls? (I also plan to create my
program on Mac OS) ?

Thank you for any hint.

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User137 · 2016-08-06 16:22

Maybe TProcess can do the same? I think that sort of general purpose
class would be made cross-platform.

http://www.freepascal.org/docs-html/fcl/process/tprocess.input.html
or
http://www.freepascal.org/docs-html/fcl/process/tprocess.output.html

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Phil · 2016-08-06 16:27

Quote from: User137 on August 06, 2016, 06:22:36 pmMaybe TProcess can
do the same?

Martin,

What he said.

I would scrap that entire approach and just use TProcess to run the
console app and capture its output.

The "300 ms sleep" sounds like a failure waiting to happen. And
doesn't that kind of defeat the purpose of running the console app in
a separate thread if you're waiting for it to complete?

The Win API calls will likely tie your code to Windows. Start over
would be my suggestion.

-Phil

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Martin V · 2016-08-06 19:11

Thank you for the tProcess.Output hint.

This page holds an explanation and a sample code:

http://wiki.freepascal.org/Executing_External_Programs#Reading_large_o
utput