16. Diagnostic: X11, FVWM and Watch Errors
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## 16. Diagnostic: X11, FVWM and Watch Errors

Most of the X11 Display Managers, such as XDM, sddm, gdm etc, are redirecting diagnostic output (standard error, stderr, file descriptor 2) into a file or some logging facility. This file is usually `$HOME/.xsession-errors`. When "Watch Errors" item is launched from default subpanel 7 (Desktop Settings), it will execute xterm -e $[infostore.xlogcmd]. If not redefined in `$FVWM_USERDIR/NsCDE.conf`, contents of the FVWM infostore variable `$[infostore.xlogcmd]` will be "tail -300f ~/.xsession-errors".

Figure 74. Watch Errors (logging)

If your X Display Manager is using different path or file name, this can be redefined in a way mentioned above. Beware that some X Display Managers (namely lightdm) are sending diagnostic output into `/dev/null`. In this case, no variable redefinition can get this output visible to the user.

Reading X, FVWM and NsCDE log output can be informative and helpful while solving possible unexpected or unexplainable problems with desktop setup.

Window Options menu (called by titlebar button 1, leftmost) of the "Watch Errors" window has a custom menu entry Fvwm Diagnostic Console which starts FVWM module FvwmConsole.

Figure 75. Personalized Window Operations Menu on "Watch Errors" window

FvwmConsole on the other hand has custom menu entry Watch Errors which calls Watch errors. When both windows are on the screen, this menu entries will simply transfer focus to each other. Both of this applications have custom Window Options Menu "NsCDE Process Manager" which will run the same named application on demand.

Figure 76. FVWM Diagnostic Console

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