Difference between QProcess and exec()

[Markus]

All,

I need to call a shell script from within my Qt 4.7 (on Linux) app and QProcess is giving me trouble.
Here is the code that does not work - meaning it does execute the shell script but the environment is false:

QProcess myProcess(this);
myProcess->start(prog, args);

QProcess myProcess(this);
myProcess->start(prog, args);

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I tried setting "PATH" and some other env-variables via myProcess->setEnvironment() but with no effect. But this works fine:

pid_t pID = fork();
if (pID == 0)  
    execl(prog,prog,args, (char *) 0);

pid_t pID = fork();
if (pID == 0)  
    execl(prog,prog,args, (char *) 0);

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Any suggestion on what is going on?

Markus