You can specify two aspects of the target system to the GNU binary file utilities, each in several ways:
In the following summaries, the lists of ways to specify values are in order of decreasing precedence. The ways listed first override those listed later.
The commands to list valid values only list the values for which the programs you are running were configured. If they were configured with --enable-targets=all, the commands list most of the available values, but a few are left out; not all targets can be configured in at once because some of them can only be configured native (on hosts with the same type as the target system).