NAME

       sd_id128_to_string, sd_id128_from_string - Format or parse 128-bit IDs as strings

SYNOPSIS

       #include <systemd/sd-id128.h>

       char *sd_id128_to_string(sd_id128_t id, char s[33]);

       int sd_id128_from_string(const char *s, sd_id128_t *ret);

DESCRIPTION

       sd_id128_to_string() formats a 128-bit ID as a character string. It expects the ID and a string array
       capable of storing 33 characters. The ID will be formatted as 32 lowercase hexadecimal digits and be
       terminated by a NUL byte.

       sd_id128_from_string() implements the reverse operation: it takes a 33 character string with 32
       hexadecimal digits (either lowercase or uppercase, terminated by NUL) and parses them back into a 128-bit
       ID returned in ret. Alternatively, this call can also parse a 37-character string with a 128-bit ID
       formatted as RFC UUID. If ret is passed as NULL the function will validate the passed ID string, but not
       actually return it in parsed form.

       Note that when parsing 37 character UUIDs this is done strictly in Big Endian byte order, i.e. according
       to RFC4122[1] Variant 1 rules, even if the UUID encodes a different variant. This matches behaviour in
       various other Linux userspace tools. It's probably wise to avoid UUIDs of other variant types.

       For more information about the "sd_id128_t" type see sd-id128(3). Note that these calls operate the same
       way on all architectures, i.e. the results do not depend on endianness.

       When formatting a 128-bit ID into a string, it is often easier to use a format string for printf(3). This
       is easily done using the SD_ID128_FORMAT_STR and SD_ID128_FORMAT_VAL() macros. For more information see
       sd-id128(3).

RETURN VALUE

       sd_id128_to_string() always succeeds and returns a pointer to the string array passed in.
       sd_id128_from_string() returns 0 on success, in which case ret is filled in, or a negative errno-style
       error code.

NOTES

       These APIs are implemented as a shared library, which can be compiled and linked to with the
       libsystemd pkg-config(1) file.

SEE ALSO

       systemd(1), sd-id128(3), printf(3)

NOTES

        1. RFC4122
           https://tools.ietf.org/html/rfc4122