What is xsession-errors?

Question

So I was looking into why a program was getting rid of my background, and the author of the program said to post .xsession-errors and many people did. Then my next question was: What is .xsession-errors? A google search reveals many results but nothing explaining what it is.

What I know so far:

• It's some kind of error log. I can't figure out what it's related too (ubuntu itself? programs?)
• I have one and it seems like all Ubuntu systems have it, though I cannot verify.

Answer 1

Linux graphical interfaces (such as GNOME) provide a way to run applications by clicking on icons instead of running them manually on the command-line. However, by doing so, output from the command-line is lost - especially the error output (STDERR).

To deal with this, some display managers (such as GDM) pipe the error output to ~/.xsession-errors, which can then be used for debugging purposes. Note that since all applications launched this way dump to the same log, it can get quite large and difficult to find specific messages.

Update: Per the documentation:

The ~/.xsession-errors X session log file has been deprecated and is no longer used.

It has been replaced by the systemd journal (journalctl command).

Answer 2

It's the error log produced by your X windows system (which the Ubuntu GUI is built on top of).

Basically it's quite a low level error log for X11.