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_is_set, sd_bus_error_has_name - 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_is_set(const sd_bus_error *e);

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

DESCRIPTION

       The sd_bus_error structure carries information about a D-Bus error condition. 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. Set an error structure to SD_BUS_ERROR_NULL in order
       to reset both fields to NULL. When no longer necessary, resources held by the
       sd_bus_errorstructure 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
       error structure again when it is not required anymore (see above). The function will
       return an errno-like negative value (see errno(3)) determined from the specified error
       name. 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). If e is NULL, no
       error structure is initialized, but the error is still converted into an errno-style
       error. If name is NULL, it is assumed that no error occurred, and 0 is returned. This
       means that this function may 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 might be set instead and
       -ENOMEM be returned. Do not use this call on error structures that are already
       initialized. If you intend to reuse an error structure, free the old data stored in it
       with sd_bus_error_free() first.

       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() can, 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 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. The absolute value is used
       implicitly. 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 the strings in e were
       set using sd_bus_set_error_const(), they will be shared. Otherwise, they will be copied.
       Returns a converted errno-like, negative error code.

       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_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(), when
       successful, return the negative errno value corresponding to the name parameter. The
       functions sd_bus_error_set_errno(), sd_bus_error_set_errnof() and
       sd_bus_error_set_errnofv(), when successful, return the negative value of the error
       parameter. If an error occurs, 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() returns 0 or a positive integer on success, and a negative error value
       converted from the error name otherwise.

       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() returns a non-zero value when e is non-NULL and the name field is
       equal to name, 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

       sd_bus_set_error() and other functions described here are available 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