diff --git a/man/print-unit-path-call-method.c b/man/print-unit-path-call-method.c new file mode 100644 index 0000000000..f73dd073f9 --- /dev/null +++ b/man/print-unit-path-call-method.c @@ -0,0 +1,51 @@ +/* SPDX-License-Identifier: MIT-0 */ + +/* This is equivalent to: + * busctl call org.freedesktop.systemd1 /org/freedesktop/systemd1 \ + * org.freedesktop.systemd1.Manager GetUnitByPID $$ + * + * Compile with 'cc print-unit-path-call-method.c -lsystemd' + */ + +#include +#include +#include +#include + +#include + +#define _cleanup_(f) __attribute__((cleanup(f))) +#define DESTINATION "org.freedesktop.systemd1" +#define PATH "/org/freedesktop/systemd1" +#define INTERFACE "org.freedesktop.systemd1.Manager" +#define MEMBER "GetUnitByPID" + +static int log_error(int error, const char *message) { + errno = -error; + fprintf(stderr, "%s: %m\n", message); + return error; +} + +int main(int argc, char **argv) { + _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL; + _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL; + _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL; + int r; + + r = sd_bus_open_system(&bus); + if (r < 0) + return log_error(r, "Failed to acquire bus"); + + r = sd_bus_call_method(bus, DESTINATION, PATH, INTERFACE, MEMBER, &error, &reply, "u", (unsigned) getpid()); + if (r < 0) + return log_error(r, MEMBER " call failed"); + + const char *ans; + r = sd_bus_message_read(reply, "o", &ans); + if (r < 0) + return log_error(r, "Failed to read reply"); + + printf("Unit path is \"%s\".\n", ans); + + return 0; +} diff --git a/man/sd_bus_call_method.xml b/man/sd_bus_call_method.xml index 762ea11c01..7b525558d7 100644 --- a/man/sd_bus_call_method.xml +++ b/man/sd_bus_call_method.xml @@ -126,6 +126,19 @@ + + Examples + + + Make a call to a D-Bus method that takes a single parameter + + + This defines a minimally useful program that will open a connection to the bus, call a method, + wait for the reply, and finally extract and print the answer. It does error handling and proper + memory management. + + + See Also