NAME
remctl_output - Retrieve the results of a remctl command
SYNOPSIS
#include <remctl.h>
struct remctl_output *remctl_output(struct remctl *r);
DESCRIPTION
remctl_output() retrieves the next output token from the remote remctl
server. 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.
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.
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
<http://www.eyrie.org/~eagle/software/remctl/>.
AUTHOR
Russ Allbery <rra@stanford.edu>