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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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SD-JSON(3) sd-json SD-JSON(3)
sd-json - APIs for Dealing with JSON Objects
#include <systemd/sd-json.h>
pkg-config --cflags --libs libsystemd
sd-json.h is part of libsystemd(3) and provides APIs to parse,
generate, format and otherwise operate with JSON objects.
The API's central data structure is JsonVariant which encapsulates
a JSON object, array, string, boolean, number or null value. These
data structures are mostly considered immutable after construction
(i.e. their contents will not change, but some meta-data might,
such as reference counters).
The APIs broadly fall into five categories:
• APIs to directly operate with JsonVariant objects, in the
sd_json_variant* namespace.
• APIs to construct complex JSON objects, in the sd_json_build*
namespace.
• APIs to map JsonVariant objects and their fields to matching
fields in C structures, in the sd_json_dispatch* namespace.
• APIs to convert a string representation of a JSON object into
a JsonVariant object, in the sd_json_parse* namespace.
• APIs to convert an JsonVariant object into its string
representation, in the sd_json_format* namespace.
This JSON library will internally encode JSON integer numbers in
the range INT64_MIN...UINT64_MAX into native 64bit signed or
unsigned integers, and will reproduce them without loss of
precision. Non-integer numbers are stored in 64bit IEEE floating
point numbers.
If the functions return string arrays, these are generally NULL
terminated and need to be freed by the caller with the libc
free(3) call after use, including the strings referenced therein.
Similarly, individual strings returned need to be freed, as well.
As a special exception, instead of an empty string array NULL may
be returned, which should be treated equivalent to an empty string
array.
Functions described here are available as a shared library, which
can be compiled against and linked to with the
libsystemd pkg-config(1) file.
The code described here uses getenv(3), which is declared to be
not multi-thread-safe. This means that the code calling the
functions described here must not call setenv(3) from a parallel
thread. It is recommended to only do calls to setenv() from an
early phase of the program when no other threads have been
started.
systemd(1), sd-varlink(3), pkg-config(1)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 258~rc2 SD-JSON(3)
Pages that refer to this page: libsystemd(3), sd_bus_message_dump(3), sd-varlink(3), systemd.directives(7), systemd.index(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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