I am trying to configure an external editor for kmail, but the way the command line is parsed makes things overly difficult. What I found out, by trials and errors:

I one enters
xterm -fa 'Liberation Mono' ...
it will not work because the program runs with argv[1]="-fa"; argv[2]="'Liberation"; argv[3]="Mono'"

One should use xterm -fa "Liberation Mono" instead. Not intuitive.

I didn't find a way to specify a line number for the vim family of editors. The command line argument is
vim +42 foobar
the following will also work in a shell
vim "+ 42" foobar; vim '+ 42' foobar; vim +\ 42 foobar

There is no way to make kmail generate one of those:

vim +%l %f  fails because some space is put between variable interpolations and one finally gets
argv[1]="+" argv[2]="42".

vim '+%l' %f fails because it gives argv[1]="'+" and argv[2]="42'".

vim "+%l" %f fails because variables are not interpolated between double quotes: it gives argv[1]="+%l".

This is really annoying and contradictory to what one might expect. Am I supposed to write a shell wrapper to send an external editor ? At some point, kmail should stop trying to parse the string too much. It should just replace %l %f and %w by their values, whereever they appear, and then simply call system() to interpolate the arguments, interpret the quotes, etc. It would be much less unexpected!

(By the way, why not add a %c to specify a column number ?) 

Reproducible: Always