source: web/old/remctl-2.14/docs/api/remctl_output.pod @ f6f3e91

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remctl API Allbery

=head1 NAME

remctl_output - Retrieve the results of a remctl command

=head1 SYNOPSIS

#include <remctl.h>

struct remctl_output *B<remctl_output>(struct remctl *I<r>);

=head1 DESCRIPTION

remctl_output() retrieves the next output token from the remote remctl
server.  I<r> is a remctl client object created with remctl_new(), which
should have previously been used as the argument to remctl_open() and then
either remctl_command() or remctl_commandv().

The returned remctl_output struct has the following members:

    struct remctl_output {
        enum remctl_output_type type;
        char *data;
        size_t length;
        int stream;                 /* 1 == stdout, 2 == stderr */
        int status;                 /* Exit status of remote command. */
        int error;                  /* Remote error code. */
    };

where the type field will have one of the following values:

    REMCTL_OUT_OUTPUT
    REMCTL_OUT_STATUS
    REMCTL_OUT_ERROR
    REMCTL_OUT_DONE

A command rejected by the remctl server will return a single output token
of type REMCTL_OUT_ERROR.  A successful command will return zero or more
REMCTL_OUT_OUTPUT tokens representing the output of the command followed
by a REMCTL_OUT_STATUS token giving the exit status of the command.
Therefore, for each command issued, the caller should call
remctl_command() or remctl_commandv() and then call remctl_output()
repeatedly to retrieve each output token until remctl_output() returns a
token of type REMCTL_OUT_ERROR or REMCTL_OUT_STATUS.

A REMCTL_OUT_OUTPUT token will have data in the data field, whose length
is given by the length field.  The output stream will be given by the
stream field, with a value of 1 indicating standard output and a value of
2 indicating standard error.  All other stream values are reserved for
future use.

A REMCTL_OUT_STATUS token will hold the exit status of the remote command
in the status field.  Following the standard Unix convention, a 0 status
should normally be considered success and any non-zero status should
normally be considered failure, although a given command may have its own
exit status conventions.

A REMCTL_OUT_ERROR token will have the error message from the server in
the data field (with length stored in length) and the protocol error code
in the error field.  The latter is the most reliable indicator of the
error; the message stored in the error field is free-form text, may or may
not be localized, and should not be used for programmatic comparisons.
For the possible error code values and their meanings, see the remctl
protocol specification.

If remctl_output() is called when there is no pending output from the
remote server (after a REMCTL_OUT_ERROR or REMCTL_OUT_STATUS token has
already been returned, for example), a token of type REMCTL_OUT_DONE will
be returned.  REMCTL_OUT_DONE tokens do not use any of the other fields of
the remctl_output struct.

The returned remctl_output struct must not be freed by the caller.  It
will be invalidated on any subsequent call to any other remctl API
function other than remctl_error() on the same remctl client object; the
caller should therefore copy out of the remctl_output struct any data it
wishes to preserve before making any subsequent remctl API calls.

=head1 RETURN VALUE

remctl_output() returns a pointer to a remctl_output struct on success and
NULL on failure.  On failure, the caller should call remctl_error() to
retrieve the error message.

=head1 SEE ALSO

remctl_new(3), remctl_open(3), remctl_command(3), remctl_commandv(3),
remctl_error(3)

The current version of the remctl library and complete details of the
remctl protocol are available from its web page at
L<http://www.eyrie.org/~eagle/software/remctl/>.

=head1 AUTHOR

Russ Allbery <rra@stanford.edu>

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