+Runs a command on all build architectures.
+.PP
+For each build architecture
+.IR arch ,
+\*(sw finds a host with the appropriate architecture, by choosing either
+the local host or reading the hostname from the
+.B archtab
+file. It then performs the following actions on that host:
+.HP 1.
+Sets the current directory to be the subdirectory named
+.I arch
+of the directory from which the command was issued. This directory is
+created if it doesn't already exist.
+.HP 2.
+Sets up an environment constructed from the environment prevailing when
+the command was issued, the default environment set up by
+.B rsh
+(or whatever equivalent remote execution program was actually used), and
+the
+.B sw\-env
+files, as described in the section
+.B "Remote environment"
+below.
+.HP 3.
+Executes the program named
+.I command
+passing it the given
+.IR argument s.
+.PP
+Output from the command is both appended to the file
+.IB arch/.build-log
+and output in some
+.IR "output style" ,
+as specified by the
+.RB ` \-o '
+command-line option. See the section
+.B "Output styles"
+below for more details.
+.PP
+If the
+.RB ` \-i '
+option was given on the command line, each architecture on which the
+command succeeds (i.e., reports a zero exit code) is marked as
+.IR "successfully built" ,
+and further build commands will not affect it unless the
+.RB ` \-f '
+command line option is passed, until a
+.B reset
+command is performed.