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Annotation of loncom/clusteradmin, revision 1.1

1.1     ! foxr        1: #!/usr/bin/perl
        !             2: 
        !             3: =pod
        !             4: 
        !             5: =head1 SYNOPSIS
        !             6: 
        !             7:  clusteradmin command [args]
        !             8: 
        !             9: =head1 DESCRIPTION
        !            10: 
        !            11: Performs an adiminstrative action on all hosts in the current dns_hosts.tab
        !            12: file.  For this to work, the current host must be the cluster administrator
        !            13: on the target systems.  That is this must be a host in managers.tab
        !            14: Furthermore, lonc must be running on this system.
        !            15: 
        !            16: The action is specified by the 'command' parameter which may have additional arguments.
        !            17: 
        !            18: All communications with remote clients are made critical so that
        !            19: they will eventually happen even if the host we want to talk with
        !            20: is dead.
        !            21: 
        !            22: 
        !            23: =head1 ACTIONS
        !            24: 
        !            25: =over 3
        !            26: 
        !            27: =item help 
        !            28: 
        !            29: Outputs a brief description of the actions supported and what they do.
        !            30: 
        !            31: =item update file
        !            32: 
        !            33: Update the contents of an administrative file with the contents of that file 
        !            34: on this system.  'file' is the name of that file, not the path for example:
        !            35: 
        !            36:   clusteradmin update dns_hosts.tab
        !            37: 
        !            38: =back
        !            39: 
        !            40: 
        !            41: =cut
        !            42: 
        !            43: use strict;
        !            44: 
        !            45: 
        !            46: #----------------------------------------------------------------------------------
        !            47: #
        !            48: #  Command dispatch handling:
        !            49: 
        !            50: #
        !            51: #   Dispatch hash for the subcommands.  
        !            52: #   indexed by the subcommand name, each item is 
        !            53: #   a reference to the sub that handles the command:
        !            54: #
        !            55: 
        !            56: my %Dispatch;
        !            57: 
        !            58: #
        !            59: #  Define a subcommand:
        !            60: #
        !            61: # Parameters:
        !            62: #    command   - subcommand name string
        !            63: #    handler   - reference to the handler sub.
        !            64: # Notes:
        !            65: #   The handler is dispatched to with the tail of the command 
        !            66: #   as an array reference parameter.  Suppose the command  is
        !            67: #
        !            68: #   clusteradmin update dns_hosts.tab, 
        !            69: #
        !            70: #   the array will have a single element:  'dns_hosts.tab'.
        !            71: #
        !            72: sub define_command {
        !            73:     my ($command, $handler)  = @_;
        !            74: 
        !            75:     $Dispatch{$command} = $handler;
        !            76: }
        !            77: 
        !            78: #
        !            79: #   Dispatch to a command:
        !            80: # Parameters:
        !            81: #   command    - Name of the command.
        !            82: #   tail       - Reference to the command tail array.
        !            83: # Returns:
        !            84: #   1          - Success.
        !            85: #   0          - Failure
        !            86: # Notes:
        !            87: # 1.  The command handler is assumed to have output any error messages
        !            88: #     to stderr by now.
        !            89: # 2.  This function will indicate to stderr if the command isn't in the
        !            90: #     dispatch hash.
        !            91: #
        !            92: sub dispatch_command {
        !            93:     my ($command, $tail) = @_;
        !            94:     my $sub;
        !            95: 
        !            96:     if (exists($Dispatch{$command})) {
        !            97: 	$sub = $Dispatch{$command};
        !            98: 	return $sub->($tail);
        !            99:     } else {
        !           100: 	print STDERR "Unrecognized subcommand keyword $command\n";
        !           101: 	&usage();
        !           102: 	return 0;
        !           103:     }
        !           104: }
        !           105: #-----------------------------------------------------------------------------------