xargs exits immediatly when you simulate exitcodes 124, 125, 126, 127. what for is that? in my opinion unsusable.

for backwards compatibility it should be new option to xargs that will make continue running if it is sense. a lot of commands returns 255. for example SVN client when repo is unavailable.

This info isn't present in the Ubuntu man page. All I see there regarding this matter is:

If any invocation of the command exits with a status of 255,
xargs will stop immediately without reading any further input.
An error message is issued on stderr when this happens.

Is this an Ubuntu/Debian bug in the man page?

Please also provide a URL link to the official POSIX web page/document that you quoted.

Here is an example:

$ echo 1 2 3 4 5 6 | xargs -n 1 badexec-name
xargs: badexec-name: No such file or directory

What I expect is that "xargs" tries to execute "badexec-name" for every command line argument from "1" to "6". Total of six execution tries. Similar to the following concept:

$ echo 1 2 3 4 5 6 | xargs -n 1 rm
rm: cannot remove `1': No such file or directory
rm: cannot remove `2': No such file or directory
rm: cannot remove `3': No such file or directory
rm: cannot remove `4': No such file or directory
rm: cannot remove `5': No such file or directory
rm: cannot remove `6': No such file or directory

Being unable to exec() a binary shouldn't be handled in a special way by stopping to process the incoming command-line arguments, and exiting prematurely. A call to exec() could fail for many reasons and some of them are non-permanent, meaning that the next call to exec() for the same command could be successful.