How does sshd know to invoke shell?

Question

When I type ssh remote-host command, sshd will run bash -c command for me.

How does sshd know to invoke bash with -c option?

Answer 1

Oh dammit, this is hardcoded in OpenSSH's source code.

From session.c of OpenSSH 5.9p1 source code:

/*
 * Execute the command using the user's shell.  This uses the -c
 * option to execute the command.
 */
argv[0] = (char *) shell0;
argv[1] = "-c";
argv[2] = (char *) command;
argv[3] = NULL;
execve(shell, argv, env);
perror(shell);
exit(1);

So I guess this is a POSIX standard huh?