.\"	$OpenBSD: fuse_opt.3,v 1.2 2018/07/08 06:17:10 jmc Exp $
.\"
.\" Copyright (c) Ray Lai <ray@raylai.com>
.\" Copyright (c) Helg Bredow <helg@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: July 8 2018 $
.Dt FUSE_OPT 3
.Os
.Sh NAME
.Nm FUSE_ARGS_INIT ,
.Nm FUSE_OPT_IS_OPT_KEY ,
.Nm FUSE_OPT_KEY ,
.Nm fuse_opt_add_arg ,
.Nm fuse_opt_insert_arg ,
.Nm fuse_opt_add_opt ,
.Nm fuse_opt_add_opt_escaped ,
.Nm fuse_opt_free_args ,
.Nm fuse_opt_match ,
.Nm fuse_opt_parse
.Nd FUSE argument and option parser
.Sh SYNOPSIS
.In fuse_opt.h
.Ft struct fuse_args
.Fo FUSE_ARGS_INIT
.Fa "int argc"
.Fa "char argv**"
.Fc
.Ft int
.Fo FUSE_OPT_IS_OPT_KEY
.Fa "fuse_opt *t"
.Fc
.Ft struct fuse_opt
.Fo FUSE_OPT_KEY
.Fa "const char *templ"
.Fa "int key"
.Fc
.Ft int
.Fo fuse_opt_add_arg
.Fa "struct fuse_args *args"
.Fa "const char *arg"
.Fc
.Ft int
.Fo fuse_opt_insert_arg
.Fa "struct fuse_args *args"
.Fa "int pos"
.Fa "const char *opt"
.Fc
.Ft int
.Fo fuse_opt_add_opt
.Fa "char **opts"
.Fa "const char *opt"
.Fc
.Ft int
.Fo fuse_opt_add_opt_escaped
.Fa "char **opts"
.Fa "const char *opt"
.Fc
.Ft void
.Fo fuse_opt_free_args
.Fa "struct fuse_args *args"
.Fc
.Ft int
.Fo fuse_opt_match
.Fa "const struct fuse_opt *opts"
.Fa "const char *opt"
.Fc
.Ft int
.Fo fuse_opt_parse
.Fa "struct fuse_args *args"
.Fa "void *data"
.Fa "const struct fuse_opt *opts"
.Fa "fuse_opt_proc_t proc"
.Fc
.Sh DESCRIPTION
These FUSE library functions and macros provide support for complex
argument and option parsing.
These are typically entered on the command line
but may also be passed by file systems to the
.Xr fuse_mount 3
and
.Xr fuse_new 3
functions.
.Ft struct fuse_args
holds string options in an array:
.Bd -literal -offset indent
struct fuse_args {
        int argc;	/* argument count */
        char **argv;	/* NULL-terminated array of arguments */
        int allocated;	/* argv was allocated and must be freed */
};
.Ed
.Pp
.Bl -tag -width Ds -compact
.It Fn FUSE_OPT_KEY templ key
returns a
.Fa struct fuse_opt
template that matches an argument or option
.Fa templ
with option key
.Fa key .
This macro is used as an element in
.Fa struct fuse_opt
arrays to create a template that is processed by a fuse_opt_proc_t.
The special constants FUSE_OPT_KEEP and FUSE_OPT_DISCARD can be specified if
proc does not need to handle this option or argument; proc is not called in
this case.
.Pp
.It Fn FUSE_OPT_IS_OPT_KEY templ
checks if
.Fa templ
is an option key.
.Pp
The last element of the
.Fa opts
.Ft struct fuse_opt
option array must be
.Dv FUSE_OPT_END .
.Pp
.Fa proc
points to a function with the following signature:
.Ft int (*fuse_opt_proc_t)
.Fo proc
.Fa "void *data"
.Fa "const char *arg"
.Fa "int key"
.Fa "struct fuse_args *outargs"
.Fc
.Pp
Special key values:
.Bd -literal -offset indent
FUSE_OPT_KEY_OPT	/* no match */
FUSE_OPT_KEY_NONOPT	/* non-option */
FUSE_OPT_KEY_KEEP	/* don't process; return 1 */
FUSE_OPT_KEY_DISCARD	/* don't process; return 0 */
.Ed
.Pp
.It Fn FUSE_ARGS_INIT
initializes a
.Ft struct fuse_args
with
.Fa argc
and
.Fa argv ,
which are usually obtained from
.Fn main .
.Fa argv
is NULL-terminated, and is suitable for use with
.Xr execvp 3 .
.Fa argv
is used directly and
.Fa allocated
is set to 0.
.Pp
.It Fn fuse_opt_add_arg
adds a single option to the end of
.Fa args .
If
.Fa args->allocated
is 0,
.Fa args->argv
is copied to the heap and
.Fa args->allocated
is set to a non-zero value.
.Pp
.It Fn fuse_opt_insert_arg
inserts a single argument at position
.Fa pos
into
.Fa args ,
shifting
.Fa args->argv
as needed.
.Pp
.It Fn fuse_opt_add_opt
adds an option
.Fa opt
to a comma-separated string of options
.Fa opts .
.Fa *opts
can be NULL, which is typically used when adding the first option.
.Pp
.It Fn fuse_opt_add_opt_escaped
escapes any
.Sq ","
and
.Sq "\\"
characters in
.Fa opt
before adding it to
.Fa opts .
.Pp
.It Fn fuse_opt_free_args
frees
.Fa args->argv
if it was allocated
.Fa args
and initializes everything to 0.
.Pp
.It Fn fuse_opt_match
tests if the argument or option
.Fa opt
appears in the list of templates
.Fa opts .
If
.Fa opt
is an option then it must not include the -o prefix.
.Pp
.It Fn fuse_opt_parse
parses options, setting any members of
.Fa data
automatically depending on the format of the template.
If
.Fa proc
is not NULL, then this is called for any argument that matches a template
with that has
.Fa val
= FUSE_OPT_KEY.
.Fa opts
is an array of
.Ft struct fuse_opt ,
each of which describes actions for each option:
.Bd -literal -offset indent
struct fuse_opt {
        const char *templ;	/* template for option */
        unsigned long off;	/* data offset */
        int val;		/* key value */
};
.Ed
.Pp
The following templates are supported.
foo=
.Pp
foo=%u %u can be any format that can be parsed by
.Fn sscanf 3 .
If this is %s then a copy of the string is allocated.
foo=bar matches the option exactly (treated the same as if it didn't have an =).
.Pp
foo matches exactly
.Pp
-b or --bar matches the argument
"-b " or "--bar " (trailing space) argument expects a value, that is passed to
.Fa proc
.Pp
-b %u or:w
 --bar %u Treated the same as foo=%u above
.Pp
Each argument or option is matched against every template.
This allows more than one member of
.Fa data
to be set by a single argument or option (see example for gid below).
.El
.Sh RETURN VALUES
.Fn fuse_opt_add_arg ,
.Fn fuse_opt_insert_arg ,
.Fn fuse_opt_add_opt ,
.Fn fuse_opt_add_opt_escaped ,
and
.Fn fuse_opt_parse
return 0 on success, -1 on error.
.Pp
.Fn fuse_opt_match
returns 1 on match, 0 if no match.
.Sh EXAMPLES
.Bd -literal -offset indent
struct foo_config {
	char *foor;
	int bar;
};

#define FOO_OPT(t, m) {t, offsetof(struct foo_config, m), 1}

struct fuse_opt opts[] {
	FUSE_OPT_KEY("--foo ",	KEY_FOO),
	FOO_OPT("-b",		bar),
	FOO_OPT("gid=",		set_gid), /* set to 1 if present */
	FOO_OPT("gid=%u",	gid),   /* set to parsed value of %u */
	FUSE_OPT_END
}

int
foo_process_proc(void *data, int key, char *val, struct fuse_args *args)
{
	foo_cofig *conf = data;

	switch(key)
	{
	case KEY_FOO:
		/* Do something... */
		conf.foo = val;
		return (0); /* discard */
	}

	/* didn't process so keep the option */
	return (1);
}

int
main(int argc, char *argv[])
{
	struct fuse_args args = FUSE_ARGS_INIT(argc, argv);

	if (fuse_opt_parse(opts, config, foo_process_proc) != 0) {
	...
.Ed
.Sh ERRORS
.Fn fuse_opt_add_arg ,
.Fn fuse_opt_insert_arg ,
.Fn fuse_opt_add_opt ,
and
.Fn fuse_opt_add_opt_escaped
can run out of memory and set
.Va errno .
.Sh SEE ALSO
.Xr fuse_main 3
.Sh STANDARDS
These library functions conform to FUSE 2.6.
.Sh HISTORY
These functions first appeared in
.Ox 5.4 .
.Sh AUTHORS
.An Sylvestre Gallon Aq Mt ccna.syl@gmail.com
.An Helg Bredow Aq Mt xx404@msn.com
.Pp
This manual was written by
.An Ray Lai Aq Mt ray@raylai.com
and updated by
.An Helg Bredow Aq Mt xx404@msn.com