On Fri, 12 Dec 2008, Bart wrote:
> Hi, > > Just played with TProcess for the first time. (I come from Delphi 3) > I observed some oddities (?, or maybe I'm just dumb ...). > > If you try to execute a process that is non-executable (like for > example a word doc), then on Windows an exception is raised and > GetLastOSError returns 193. > > If you try this on (my) linux, no exception is raised and a > non-functional childprocess is forked (you can see it with ps ax). This is because it is not waited for. > If you do this in a GTK 1 app, however, then the app gets killed. > No errormessage, it just disappears. > On the console you can se some errormessage: > Xlib: unexpected async reply (sequence 0x4cf) > > In GTK 2 app, there is no crash. > > So 3 questions: > > 1. > Shouldn't trying to execute a non-executable file raise some kind > of exception (like it does in Windows)? You cannot do this reliably. Starting a new process in linux is a 2-step algorithm: 1 Fork a clone of the current process. 2 Execute the program that you want executed. If step 2 fails, then there is no way to return an error message to the parent process except a run-error code (127, I believe). > If you try to execute a non-executable file from the console and query > for the exitcode that bash returns, it will return an exitcode of 126, > meaning: "Command invoked cannot execute" (Permission problem or > command is not an executable) > (This errorcode is not known to the syserrormessage function b.t.w.) No, because this is bash-specific. > > 2. > Why does the GTK 1 app crash? This might be a GTK bug and not fpc related. I don't think it is fpc related. > > 3. > As a way to work arond this (and at least preventing the crash): is > there a reliable way of cheking that a file can be executed in the > first place? I know I can check for the execute permission of the file > in question, but that is not enough (on my system any file copied from > my windows partition to linux will have the x permission set). You can use the fpaccess() call with X_OK for this; But it is not a bullet-proof guarantee. You must know for sure which file exactly will be executed. > > I tend to try to make my (silly) programs foolproof, so it would be > nice if either TProcess.Execute raises an error for this or I can > implement my workaraound, so I can present the user with an > appropriate errormessage, and not the app crash on him, or in the eyes > of the user do nothing at all, when the user expects it to execute > some other program... Well, you can try using fpaccess. Michael. _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
