The third argument to argp parser functions (see Argp Parser Functions) is a pointer to a
struct argp_state, which contains
information about the state of the option parsing.
This structure has the following fields, which may be modified as noted:
const struct argp *const root_argp
The top level argp parser being parsed. Note that this is often
not the same
struct argp passed into
the invoking program. See Parsing Program Options with Argp. It is an internal argp parser that
contains options implemented by
argp_parse itself, such as
The argument vector being parsed. This may be modified.
The index in
argv of the next argument to be parsed. This may be
One way to consume all remaining arguments in the input is to set
state->next = state->argc, perhaps after recording
the value of the
next field to find the consumed arguments. The
current option can be re-parsed immediately by decrementing this field,
state->argv[state->next] to reflect
the option that should be reexamined.
The flags supplied to
argp_parse. These may be modified, although
some flags may only take effect when
argp_parse is first
invoked. See Flags for
While calling a parsing function with the key argument
ARGP_KEY_ARG, this represents the number of the current arg,
starting at 0. It is incremented after each
returns. At all other times, this is the number of
arguments that have been processed.
If non-zero, the index in
argv of the first argument following a
special ‘--’ argument. This prevents anything that follows from
being interpreted as an option. It is only set after argument parsing
has proceeded past this point.
An arbitrary pointer passed in from the caller of
the input argument.
These are values that will be passed to child parsers. This vector will
be the same length as the number of children in the current parser. Each
child parser will be given the value of
state->child_inputs[i] as its
state->input field, where i is the index of the child
in the this parser’s
children field. See Combining Multiple Argp Parsers.
For the parser function’s use. Initialized to 0, but otherwise ignored by argp.
The name used when printing messages. This is initialized to
The stdio streams used when argp prints. Error messages are printed to
err_stream, all other output, such as ‘--help’ output) to
out_stream. These are initialized to
stdout respectively. See Standard Streams.
Private, for use by the argp implementation.