DESCRIPTION
The uuidgen system call generates count universally unique identifiers (UUIDs) and writes them to the buffer pointed to by store. The identifiers are generated according to the syntax and semantics of the DCE version 1 variant of universally unique identifiers. See below for a more in-depth description of the identifiers. When no IEEE 802 address is available for the node field, a random multicast address is generated for each invocation of the system call. According to the algorithm of generating time-based UUIDs, this will also force a new random clock sequence, thereby increasing the likelihood for the identifier to be unique. When multiple identifiers are to be generated, the uuidgen system call will generate a set of identifiers that is dense in such a way that there is no identifier that is larger than the smallest identifier in the set and smaller than the largest identifier in the set and that is not already in the set.
Universally unique identifiers, also known as globally unique identifiers (GUIDs), have a binary representation of 128-bits. The grouping and meaning of these bits is described by the following structure and its description of the fields that follow it:
struct uuid {
uint32_t time_low;
uint16_t time_mid;
uint16_t time_hi_and_version;
uint8_t clock_seq_hi_and_reserved;
uint8_t clock_seq_low;
uint8_t node[_UUID_NODE_LEN];
};
