upscli_list_start (3) - Linux Manuals

upscli_list_start: begin multi-item retrieval from a UPS

NAME

upscli_list_start - begin multi-item retrieval from a UPS

SYNOPSIS

#include <upsclient.h>
int upscli_list_start(UPSCONN_t *ups, int numq, const char **query)

DESCRIPTION

The upscli_list_start() function takes the pointer ups to a UPSCONN_t state structure, and the pointer query to an array of numq query elements. It builds a properly-formatted request from those elements and transmits it to upsd(8).

Upon success, the caller must call upscli_list_next(3) to retrieve the elements of the list. Failure to retrieve the list will most likely result in the client getting out of sync with the server due to buffered data.

USES

This function implements the "LIST" command in the protocol. As a result, you can use it to request many different things from the server. Some examples are:

• LIST UPS

• LIST VAR <ups>

• LIST RW <ups>

• LIST CMD <ups>

• LIST ENUM <ups> <var>

• LIST RANGE <ups> <var>

QUERY FORMATTING

To see the list of variables on a UPS called su700, the protocol command would be LIST VAR su700. To start that list with this function, you would populate query and numq as follows:

int numq;
const char *query[2];

query[0] = "VAR";
query[1] = "su700";
numq = 2;

All escaping of special characters and quoting of elements with spaces are handled for you inside this function.

ERROR CHECKING

This function checks the response from upsd(8) against your query. If it is not starting a list, or is starting the wrong type of list, it will return an error code.

When this happens, upscli_upserror(3) will return UPSCLI_ERR_PROTOCOL.

RETURN VALUE

The upscli_list_start() function returns 0 on success, or -1 if an error occurs.