sd-json - Man Page

#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)

libsystemd(3), sd_bus_message_dump(3), sd_json_dispatch_string(3), sd_json_parse(3), sd-varlink(3), systemd.directives(7), systemd.index(7).