sd_id128_to_string(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | NOTES | COLOPHON

SD_ID128_TO_STRING(3)      sd_id128_to_string      SD_ID128_TO_STRING(3)

NAME         top

       sd_id128_to_string, SD_ID128_TO_STRING, sd_id128_from_string,
       SD_ID128_STRING_MAX - Format or parse 128-bit IDs as strings

SYNOPSIS         top

       #include <systemd/sd-id128.h>

       #define SD_ID128_STRING_MAX 33U

       #define SD_ID128_TO_STRING(id) ...

       char
                                *sd_id128_to_string(sd_id128_t id, char s[static SD_ID128_STRING_MAX]);

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

DESCRIPTION         top

       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 (SD_ID128_STRING_MAX). The ID will be formatted as 32
       lowercase hexadecimal digits and be terminated by a NUL byte.

       SD_ID128_TO_STRING() is a macro that wraps sd_id128_to_string()
       and passes an appropriately sized buffer as second argument,
       allocated as C99 compound literal. Each use will thus implicitly
       acquire a suitable buffer on the stack which remains valid until
       the end of the current code block. This is usually the simplest
       way to acquire a string representation of a 128-bit ID in a
       buffer that is valid in the current code block.

       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         top

       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         top

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

SEE ALSO         top

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

NOTES         top

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

COLOPHON         top

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systemd 249                                        SD_ID128_TO_STRING(3)

Pages that refer to this page: sd_bus_set_address(3)sd-id128(3)