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nbdkit_realpath(3)		    NBDKIT		    nbdkit_realpath(3)

NAME
       nbdkit_realpath,	nbdkit_absolute_path - convert relative	to absolute
       paths for nbdkit

SYNOPSIS
	#include <nbdkit-plugin.h>

	char *nbdkit_realpath (const char *filename);
	char *nbdkit_absolute_path (const char *filename);

DESCRIPTION
       nbdkit(1) usually (not always) changes directory	to / before it starts
       serving connections.  This means	that any relative paths	passed during
       configuration will not work when	the server is running.	In a naive
       implementation of a plugin, a configuration like

	nbdkit plugin file=disk.img

       might attempt to	open /disk.img instead of the file in the user's
       current directory.

       To avoid	this problem, you can:

          convert relative paths to absolute paths using one of the functions
	   described here, or

          open	the file at configure time and store the file descriptor.

   nbdkit_realpath
       The utility function "nbdkit_realpath" converts any path	to an absolute
       path, resolving symlinks.  Under	the hood it uses the realpath(3)
       function, and thus it fails if the path does not	exist, or it is	not
       possible	to access components of	the path.

       This function works only	when used in the ".config", ".config_complete"
       and ".get_ready"	callbacks.

   nbdkit_absolute_path
       The utility function "nbdkit_absolute_path" converts any	path to	an
       absolute	path: if it is relative, then all this function	does is
       prepend the current working directory to	the path, with no extra
       checks.

       Unlike "nbdkit_realpath", this function does not	check that the file
       exists.

       This function works only	when used in the ".config", ".config_complete"
       and ".get_ready"	callbacks.

RETURN VALUE
       On success these	functions return a newly allocated string.  The
       returned	string must be freed by	the caller.

       On error	these call nbdkit_error(3) and return "NULL".

LANGUAGE BINDINGS
       In nbdkit-ocaml-plugin(3):

	NBDKit.realpath	: string -> string

HISTORY
       "nbdkit_absolute_path" was present in nbdkit 0.1.0.

       "nbdkit_realpath" was added in nbdkit 1.4.

SEE ALSO
       nbdkit(1), nbdkit-plugin(3), nbdkit-filter(3).

AUTHORS
       Richard W.M. Jones

COPYRIGHT
       Copyright Red Hat

LICENSE
       Redistribution and use in source	and binary forms, with or without
       modification, are permitted provided that the following conditions are
       met:

          Redistributions of source code must retain the above	copyright
	   notice, this	list of	conditions and the following disclaimer.

          Redistributions in binary form must reproduce the above copyright
	   notice, this	list of	conditions and the following disclaimer	in the
	   documentation and/or	other materials	provided with the
	   distribution.

          Neither the name of Red Hat nor the names of	its contributors may
	   be used to endorse or promote products derived from this software
	   without specific prior written permission.

       THIS SOFTWARE IS	PROVIDED BY RED	HAT AND	CONTRIBUTORS ''AS IS'' AND ANY
       EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
       IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
       PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
       LIABLE FOR ANY DIRECT, INDIRECT,	INCIDENTAL, SPECIAL, EXEMPLARY,	OR
       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
       SUBSTITUTE GOODS	OR SERVICES; LOSS OF USE, DATA,	OR PROFITS; OR
       BUSINESS	INTERRUPTION) HOWEVER CAUSED AND ON ANY	THEORY OF LIABILITY,
       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
       OTHERWISE) ARISING IN ANY WAY OUT OF THE	USE OF THIS SOFTWARE, EVEN IF
       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

nbdkit-1.46.0			  2026-03-04		    nbdkit_realpath(3)

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