SD_BUS_ERROR(3)                 sd_bus_error                 SD_BUS_ERROR(3)

NAME         top

       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         top

       #include <systemd/sd-bus.h>

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

       SD_BUS_ERROR_MAKE_CONST(name, message)


       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         top

       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         top

       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.


       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         top

       Returned errors may indicate the following problems:

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

           Memory allocation failed.

NOTES         top

       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         top

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

NOTES         top

        1. Valid Names

COLOPHON         top

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systemd 233                                                  SD_BUS_ERROR(3)