[U-Boot-Users] Capture of the returned value in cmdline

[do]

Hello,
Is this possible to capture value returned by the function, which 
implement some command (for example do_printenv),
from commandline in u-boot and for example write it to some shell variable?
Is this also possible with standalone programs like examples/hello_world.c?


By the way, what is the usage/application of the flag argument in 
command function declaration, for example:
int do_printenv(cmd_tbl_t * cmdtp, int flag, int argc, char * argv[]);

Best regards!