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IABSD.fr/src/lib/libfuse/fuse_opt.3
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.\" $OpenBSD: fuse_opt.3,v 1.9 2026/03/14 10:47:00 helg 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. .\" .\" 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: March 14 2026 $ .Dt FUSE_OPT 3 .Os .Sh NAME .Nm FUSE_ARGS_INIT , .Nm FUSE_OPT_IS_OPT_KEY , .Nm FUSE_OPT_KEY , .Nm FUSE_OPT_END , .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 .Lb libfuse .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 struct fuse_opt .Fn FUSE_OPT_END .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 .Ft typedef int .Fo (*fuse_opt_proc_t) .Fa "void *data" .Fa "const char *arg" .Fa "int key" .Fa "struct fuse_args *outargs" .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_ARGS_INIT initializes a .Ft struct fuse_args with .Fa argc and .Fa argv , which are usually obtained from .Fn main . .Fa argv is .Dv NULL Ns -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_free_args If .Fa args is allocated, free .Fa args->argv and zero all members of .Fa args . Otherwise, do nothing. .Pp .It Fn FUSE_OPT_KEY templ key Return a .Fa struct fuse_opt template that matches an argument or option .Vt templ with option key .Vt key . This macro is used as an element in .Fa struct fuse_opt arrays to create a template that is processed by a .Vt fuse_opt_proc_t . The special constants .Dv FUSE_OPT_KEY_KEEP and .Dv FUSE_OPT_KEY_DISCARD can be specified for .Fa val if .Fa proc does not need to handle this option or argument; .Fa proc is not called in this case. .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 special key values can be used for .Fa val : .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 .It Fn FUSE_OPT_END The last element of each .Fa "struct fuse_opt *opts" array passed to any function must be .Dv FUSE_OPT_END . .Pp .It Fn FUSE_OPT_IS_OPT_KEY templ Check whether .Fa templ is an option key. .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 .Dv NULL , which is typically used when adding the first option. .Pp .It Fn fuse_opt_add_opt_escaped escapes any .Sq ,\& and .Sq \e characters in .Fa opt before adding it to .Fa opts . .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 .Dv NULL , then this is called for any argument that matches a template that has .Fa offset No = Dv FUSE_OPT_KEY_OPT . .Fa opts is an array of .Ft struct fuse_opt , each of which describes actions for each option: .Pp The following templates are supported as options and must be preceded by .Fl o in the list of arguments, with or without a space between .Fl o and the option. If multiple options are specified they can be comma separated or specified individually with .Fl o each time. For example, these are all valid: .Bd -unfilled -offset indent .Fl o Ar foo .Sm off .Fl o Ar bar .Fl o Ar foo , bar .Sm on .Ed .Pp foo matches exactly .Pp foo= matches exactly .Pp foo=bar matches the option exactly (treated the same as if it didn't have an =). .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. .Pp Arguments .Pp -b or --bar matches the argument and sets the value of the struct at offset to key. .Pp .Qq Fl b Ns \ \& or .Qq Fl \-bar Ns \ \& (trailing space) argument expects a value, the whole argument, including -b, is passed to .Fa proc .Pp .Qq Fl b Ar %u or .Qq Fl \-bar Ar %u is 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). .Pp .It Fn fuse_opt_proc_t The fuse_opt_proc_t function takes the following arguments. .Bl -tag -width Ds .It Fa data data argument passed to .Fn fuse_opt_parse .It Fa arg the whole argument or option .It Fa key is the key defined with the option or one of the special keys. .It Fa outargs The current list of arguments .El .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 or \-1 on error. .Pp .Fn fuse_opt_match returns 1 on match or 0 if no match. .Pp The .Fn fuse_opt_proc_t callback shall return 1 to retain the option in the output argument vector, or 0 to discard it. This permits options to be preserved for subsequent processing. A return value of \-1 indicates an error condition and causes .Fn fuse_opt_parse to terminate with failure. .Sh EXAMPLES .Bd -literal #include <err.h> #include <fuse.h> #include <stddef.h> #include <stdio.h> #include <string.h> enum { KEY_FOO }; struct foo_config { char *foo; int bar; gid_t gid; int set_gid; int toggle; }; #define FOO_OPT(t, m) {t, offsetof(struct foo_config, m), 1} struct fuse_opt opts[] = { FUSE_OPT_KEY("--foo ", KEY_FOO),/* passed to foo_opt_proc() */ FOO_OPT("-b", bar), /* set to 1 if present */ FOO_OPT("toggle", toggle), /* set to 1 if present */ 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_opt_proc(void *data, const char *val, int key, struct fuse_args *args) { struct foo_config *conf = data; switch(key) { case KEY_FOO: conf->foo = strdup(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); struct foo_config config; memset(&config, 0, sizeof(config)); if (fuse_opt_parse(&args, &config, opts, foo_opt_proc) == -1) err(1, "Usage: prog [foo=value] [-b] " "[-o [gid=value],[toggle]]"); printf("foo=%s\en", config.foo); printf("toggle=%d\en", config.toggle); printf("bar=%d\en", config.bar); printf("set_gid=%d\en", config.set_gid); printf("gid=%u\en", config.gid); } .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 helg@openbsd.org .Pp This manual was written by .An Ray Lai Aq Mt ray@raylai.com and updated by .An Helg Bredow Aq Mt helg@openbsd.org