Question

I have been trying use zenity with standard re-direction in a shell script, something like

for i in $(seq 1 10); do echo $i; done | zenity –list –column =”Number”

But on the command line this works , but throws the following warning:

(zenity:3328): GLib-WARNING **: Invalid file descriptor.

This seems to happen only when data is redirected to the Zenity command through a pipe.

Could anyone please tell me what this warning signifies?

Answer 1

This error is triggered by attempting to close stdin twice – once after all the data has been read from the sequence, and then secondly as it’s just about to quit – this is in the zenity source. It’s purely cosmetic and can be safely ignored – the zenity code is doing nothing else except quitting at that point.

In the handler zenity_tree_handle_stdin, towards the end of the routine it closes the same channel (there is variable hiding caused by using the same named variable in the function and at the global scope):

if ((condition != G_IO_IN) && (condition != G_IO_IN + G_IO_HUP)) {
  g_io_channel_shutdown (channel, TRUE, NULL);
  return FALSE;
}

In tree.c ~line 648 as the program is about to exit:

  if (channel != NULL)
    g_io_channel_shutdown (channel, TRUE, NULL);

Both of these code paths will attempt to close the same channel, causing the warning. Because the next thing done after line 648 is to issue a gtk_main_quit, then I think the warning can be safely ignored.