json(3) - Linux manual page (original) (raw)

SD-JSON(3) sd-json SD-JSON(3)

NAME top

   sd-json - APIs for Dealing with JSON Objects

SYNOPSIS top

   **#include <systemd/sd-json.h>**

   **pkg-config --cflags --libs libsystemd**

DESCRIPTION top

   sd-json.h is part of [libsystemd(3)](../man3/libsystemd.3.html) 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)](../man3/free.3.html) 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.

NOTES top

   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)](../man3/getenv.3.html), which is declared to be
   not multi-thread-safe. This means that the code calling the
   functions described here must not call [setenv(3)](../man3/setenv.3.html) 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.

SEE ALSO top

   [systemd(1)](../man1/systemd.1.html), [sd-varlink(3)](../man3/sd-varlink.3.html), **pkg-config**(1)

COLOPHON top

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   This page was obtained from the project's upstream Git repository
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   man-pages@man7.org

systemd 258~devel SD-JSON(3)

Pages that refer to this page:libsystemd(3), sd_json_variant_unset_field(3), sd-varlink(3), systemd.directives(7), systemd.index(7)