why can't QProcess read all output?

[Raul]

hi guys!
I'm using QProcess start a program,but I'm come across a problem.the problem is when I read the QProcess,it doesn't read all of the output.eg,actually,the output should be two lines,but it shows only one line.what's wrong with it?If someone can help me?thanks!

to my suprise,it sometimes can read the second line.