NAME

       sd_bus_error, SD_BUS_ERROR_MAKE_CONST, SD_BUS_ERROR_NULL, sd_bus_error_free, sd_bus_error_set,
       sd_bus_error_setf, sd_bus_error_set_const, sd_bus_error_set_errno, sd_bus_error_set_errnof,
       sd_bus_error_set_errnofv, sd_bus_error_get_errno, sd_bus_error_copy, sd_bus_error_move,
       sd_bus_error_is_set, sd_bus_error_has_name, sd_bus_error_has_names_sentinel, sd_bus_error_has_names -
       sd-bus error handling

SYNOPSIS

       #include <systemd/sd-bus.h>

       typedef struct {
               const char *name;
               const char *message;
               ...
       } sd_bus_error;

       SD_BUS_ERROR_MAKE_CONST(name, message)

       SD_BUS_ERROR_NULL

       void sd_bus_error_free(sd_bus_error *e);

       int sd_bus_error_set(sd_bus_error *e, const char *name, const char *message);

       int sd_bus_error_setf(sd_bus_error *e, const char *name, const char *format, ...);

       int sd_bus_error_set_const(sd_bus_error *e, const char *name, const char *message);

       int sd_bus_error_set_errno(sd_bus_error *e, int error);

       int sd_bus_error_set_errnof(sd_bus_error *e, int error, const char *format, ...);

       int sd_bus_error_set_errnofv(sd_bus_error *e, int error, const char *format, va_list ap);

       int sd_bus_error_get_errno(const sd_bus_error *e);

       int sd_bus_error_copy(sd_bus_error *dst, const sd_bus_error *e);

       int sd_bus_error_move(sd_bus_error *dst, sd_bus_error *e);

       int sd_bus_error_is_set(const sd_bus_error *e);

       int sd_bus_error_has_name(const sd_bus_error *e, const char *name);

       int sd_bus_error_has_names_sentinel(const sd_bus_error *e, ...);

       #define sd_bus_error_has_names(e, ...) sd_bus_error_has_names_sentinel(e, ..., NULL)

DESCRIPTION

       The sd_bus_error structure carries information about a D-Bus error condition, or lack thereof. The
       functions described below may be used to set and query fields in this structure.

       •   The name field contains a short identifier of an error. It should follow the rules for error names
           described in the D-Bus specification, subsection Valid Names[1]. A number of common, standardized
           error names are described in sd-bus-errors(3), but additional domain-specific errors may be defined
           by applications.

       •   The message field usually contains a human-readable string describing the details, but might be NULL.

       An unset sd_bus_error structure should have both fields initialized to NULL, and signifies lack of an
       error, i.e. success. Assign SD_BUS_ERROR_NULL to the structure in order to initialize both fields to
       NULL. When no longer necessary, resources held by the sd_bus_error structure should be destroyed with
       sd_bus_error_free().

       sd_bus_error_set() sets an error structure to the specified name and message strings. The strings will be
       copied into internal, newly allocated memory. It is essential to free the contents again when they are
       not required anymore (see above). Do not use this call on error structures that have already been set. If
       you intend to reuse an error structure, free the old data stored in it with sd_bus_error_free() first.

       sd_bus_error_set() will return an errno-like value (see errno(3)) determined from the specified error
       name name. If name is NULL, it is assumed that no error occurred, and 0 is returned. If name is nonnull,
       a negative value is always returned. If e is NULL, no error structure is initialized, but name is still
       converted into an errno-style value.

       Various well-known D-Bus errors are converted to well-known errno counterparts, and the other ones to
       -EIO. See sd-bus-errors(3) for a list of well-known error names. Additional error mappings may be defined
       with sd_bus_error_add_map(3).

       sd_bus_error_set() is designed to be conveniently used in a return statement. If message is NULL, no
       message is set. This call can fail if no memory may be allocated for the name and message strings, in
       which case an SD_BUS_ERROR_NO_MEMORY error will be set instead and -ENOMEM returned.

       sd_bus_error_setf() is similar to sd_bus_error_set(), but takes a printf(3) format string and
       corresponding arguments to generate the message field.

       sd_bus_error_set_const() is similar to sd_bus_error_set(), but the string parameters are not copied
       internally, and must hence remain constant and valid for the lifetime of e. Use this call to avoid memory
       allocations when setting error structures. Since this call does not allocate memory, it will not fail
       with an out-of-memory condition as sd_bus_error_set() may, as described above. Alternatively, the
       SD_BUS_ERROR_MAKE_CONST() macro may be used to generate a literal, constant bus error structure
       on-the-fly.

       sd_bus_error_set_errno() will immediately return 0 if the specified error parameter error is 0.
       Otherwise, it will set name from an errno-like value that is converted to a D-Bus error.  strerror_r(3)
       will be used to set message. Well-known D-Bus error names will be used for name if applicable, otherwise
       a name in the "System.Error."  namespace will be generated. The sign of the specified error number is
       ignored and the absolute value is used implicitly. If the specified error error is non-zero, the call
       always returns a negative value, for convenient usage in return statements. This call might fail due to
       lack of memory, in which case an SD_BUS_ERROR_NO_MEMORY error is set instead, and -ENOMEM is returned.

       sd_bus_error_set_errnof() is similar to sd_bus_error_set_errno(), but in addition to error, takes a
       printf(3) format string and corresponding arguments. The message field will be generated from format and
       the arguments.

       sd_bus_error_set_errnofv() is similar to sd_bus_error_set_errnof(), but takes the format string
       parameters as va_arg(3) parameter list.

       sd_bus_error_get_errno() converts the name field of an error structure to an errno-like (positive) value
       using the same rules as sd_bus_error_set(). If e is NULL, 0 will be returned.

       sd_bus_error_copy() will initialize dst using the values in e, if e has been set with an error value
       before. Otherwise, it will return immediately. If the strings in e were set using
       sd_bus_error_set_const(), they will be shared. Otherwise, they will be copied. Returns a converted
       errno-like, negative error code or 0. Before this call, dst must be unset, i.e. either freshly
       initialized with NULL or reset using sd_bus_error_free().

       sd_bus_error_move() is similar to sd_bus_error_copy(), but will move any error information from e into
       dst, resetting the former. This function cannot fail, as no new memory is allocated. Note that if e is
       not set, dst is initialized to SD_BUS_ERROR_NULL. Moreover, if dst is NULL no operation is executed on it
       and resources held by e are freed and reset. Returns a converted errno-like, non-positive error value.

       sd_bus_error_is_set() will return a non-zero value if e is non-NULL and an error has been set, false
       otherwise.

       sd_bus_error_has_name() will return a non-zero value if e is non-NULL and an error with the same name has
       been set, false otherwise.

       sd_bus_error_has_names_sentinel() is similar to sd_bus_error_has_name(), but takes multiple names to
       check against. The list must be terminated with NULL.  sd_bus_error_has_names() is a macro wrapper around
       sd_bus_error_has_names_sentinel() that adds the NULL sentinel automatically.

       sd_bus_error_free() will destroy resources held by e. The parameter itself will not be deallocated, and
       must be free(3)d by the caller if necessary. The function may also be called safely on unset errors
       (error structures with both fields set to NULL), in which case it performs no operation. This call will
       reset the error structure after freeing the data, so that all fields are set to NULL. The structure may
       be reused afterwards.

RETURN VALUE

       The functions sd_bus_error_set(), sd_bus_error_setf(), and sd_bus_error_set_const() always return 0 when
       the specified error value is NULL, and a negative errno-like value corresponding to the name parameter
       otherwise. The functions sd_bus_error_set_errno(), sd_bus_error_set_errnof() and
       sd_bus_error_set_errnofv(), return 0 when the specified error value is 0, and a negative errno-like value
       corresponding to the error parameter otherwise. If an error occurs internally, one of the negative error
       values listed below will be returned.

       sd_bus_error_get_errno() returns false when e is NULL, and a positive errno value mapped from e->name
       otherwise.

       sd_bus_error_copy() and sd_bus_error_move() return a negative error value converted from the source
       error, and zero if the error has not been set.

       sd_bus_error_is_set() returns a non-zero value when e and the name field are non-NULL, zero otherwise.

       sd_bus_error_has_name(), sd_bus_error_has_names(), and sd_bus_error_has_names_sentinel() return a
       non-zero value when e is non-NULL and the name field is equal to one of the given names, zero otherwise.

REFERENCE OWNERSHIP

       sd_bus_error is not reference counted. Users should destroy resources held by it by calling
       sd_bus_error_free(). Usually, error structures are allocated on the stack or passed in as function
       parameters, but they may also be allocated dynamically, in which case it is the duty of the caller to
       free(3) the memory held by the structure itself after freeing its contents with sd_bus_error_free().

   Errors
       Returned errors may indicate the following problems:

       -EINVAL
           Error was already set in sd_bus_error structure when one the error-setting functions was called.

       -ENOMEM
           Memory allocation failed.

NOTES

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

SEE ALSO

       systemd(1), sd-bus(3), sd-bus-errors(3), sd_bus_error_add_map(3), errno(3), strerror_r(3)

NOTES

        1. Valid Names
           http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names