Thanks Jeff!
It looks like I have implemented what I wanted.
Example using multi page project
➜ release git:(702e8b8915) ✗ ./eeschema/eeschema test/board.kicad_sch
COMAND LINE PARSER
OpenProjectFiles (BEGIN)
Load design...
Loading file: /home/lheck/Documents/kicad-6.0.2-eeschema-min/build/release/test/board.kicad_sch
Loading file: /home/lheck/Documents/kicad-6.0.2-eeschema-min/build/release/test/female-adapter.kicad_sch
Loading file: /home/lheck/Documents/kicad-6.0.2-eeschema-min/build/release/test/mainboard.kicad_sch
Loading file: /home/lheck/Documents/kicad-6.0.2-eeschema-min/build/release/test/male-adapter.kicad_sch
OpenProjectFiles (END)
Saving project files
Output: /home/lheck/Documents/kicad-6.0.2-eeschema-min/build/release/test/board.sch
Output: /home/lheck/Documents/kicad-6.0.2-eeschema-min/build/release/test/female-adapter.sch
Output: /home/lheck/Documents/kicad-6.0.2-eeschema-min/build/release/test/mainboard.sch
Output: /home/lheck/Documents/kicad-6.0.2-eeschema-min/build/release/test/male-adapter.sch
COMAND LINE PARSER (END)
# Checkiking generated files
➜ release git:(702e8b8915) ✗ ls -ltr test/*.kicad_sch test/*.sch
-rw-rw-r-- 1 lheck lheck 14855 Mar 8 21:07 test/board.kicad_sch
-rw-rw-r-- 1 lheck lheck 13725 Mar 8 21:07 test/male-adapter.kicad_sch
-rw-rw-r-- 1 lheck lheck 144799 Mar 8 21:07 test/mainboard.kicad_sch
-rw-rw-r-- 1 lheck lheck 22197 Mar 8 21:07 test/female-adapter.kicad_sch
-rw-rw-r-- 1 lheck lheck 1568 Mar 12 19:02 test/board.sch
-rw-rw-r-- 1 lheck lheck 3576 Mar 12 19:02 test/female-adapter.sch
-rw-rw-r-- 1 lheck lheck 2444 Mar 12 19:02 test/male-adapter.sch
-rw-rw-r-- 1 lheck lheck 29319 Mar 12 19:02 test/mainboard.sch
Example using single page project
➜ release git:(702e8b8915) ✗ ./eeschema/eeschema board.kicad_sch
COMAND LINE PARSER
OpenProjectFiles (BEGIN)
Load design...
Loading file: /home/lheck/Documents/kicad-6.0.2-eeschema-min/build/release/board.kicad_sch
OpenProjectFiles (END)
Saving project files
Output: /home/lheck/Documents/kicad-6.0.2-eeschema-min/build/release/board.sch
COMAND LINE PARSER (END)
# Checking generated file
➜ release git:(702e8b8915) ✗ ls -ltr *.kicad_sch *.sch
-rw-rw-r-- 1 lheck lheck 207671 Mar 9 10:38 board.kicad_sch
-rw-rw-r-- 1 lheck lheck 41447 Mar 12 19:02 board.sch