Look up the error message corresponding to an error number.
@param errnum The error number.
@param buf A character buffer that may be used to hold the message.
@param buflen The length of the provided buffer.
@return A pointer to a character string containing the error message.
Look up the error message corresponding to an error number.
@param errnum The error number. @param buf A character buffer that may be used to hold the message. @param buflen The length of the provided buffer. @return A pointer to a character string containing the error message.