why did readyreadstandardoutput signal not work?

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29th July 2009, 08:40
sunnysun520

why did readyreadstandardoutput signal not work?

hello,everybody.
I use Qprocess to connect my c program ,but the signal readyreadstandardoutput can not connect to my slot function?
why?I channge the signal to readyreadstandardError,is works,why?
29th July 2009, 09:23
Ginsengelf

Re: why did readyreadstandardoutput signal not work?

Hi, does your connect() call fail, or do you just get no data with readyReadStandardOutput?
In the second case, your c program probably writes to stderr, not to stdout.

Ginsengelf
29th July 2009, 09:35
wagmare

Re: why did readyreadstandardoutput signal not work?

because QProcess have two seperate channels to read normal output and error

Quote:

It also emits readyReadStandardOutput() when new standard output data is available, and when new standard error data is available, readyReadStandardError() is emitted

if u want a single output use
setProcessChannelMode(QProcess::MergedChannels);
30th July 2009, 03:52
sunnysun520

Re: why did readyreadstandardoutput signal not work?

Quote:

Originally Posted by Ginsengelf

Hi, does your connect() call fail, or do you just get no data with readyReadStandardOutput?
In the second case, your c program probably writes to stderr, not to stdout.

Ginsengelf

hi ,I think it failed, because I "cout something" in the slot function,it did not display int the console .
30th July 2009, 03:57
sunnysun520

Re: why did readyreadstandardoutput signal not work?

Quote:

Originally Posted by wagmare

because QProcess have two seperate channels to read normal output and error

if u want a single output use
setProcessChannelMode(QProcess::MergedChannels);

I will try
30th July 2009, 11:45
sunnysun520

Re: why did readyreadstandardoutput signal not work?

Quote:

Originally Posted by wagmare

because QProcess have two seperate channels to read normal output and error

if u want a single output use
setProcessChannelMode(QProcess::MergedChannels);

the following is some of my src code.

connect(&process,SIGNAL(readyReadStandardOutput()) ,this,SLOT(updaterev_line()));
。。。。。
process.setProcessChannelMode(QProcess::SeparateCh annels);
process.setReadChannel(QProcess::StandardOutput);

it does not work too!(the signal can not connect the solt func!)
30th July 2009, 12:16
wagmare

Re: why did readyreadstandardoutput signal not work?

Quote:

process.setProcessChannelMode(QProcess::SeparateCh annels)
process.setReadChannel(QProcess::StandardOutput);

no need to set this one .. it is default ...

look u will receive readyReadStandardOutput() only when your external application that u are starting using QProcess should have stdOutput() .. if it is giving stdErr() then u cant receive readyReadStandardOutput() ..

only way to receive stdErr() in readyReadStandardOutput() .. merge the two channels ..

Quote:

QProcess merges the output of the running process into the standard output channel (stdout). The standard error channel (stderr) will not receive any data. The standard output and standard error data of the running process are interleaved.