GET9ROOT(3)

NAME
get9root, unsharp - get path to root of Plan 9 tree

SYNOPSIS
#include <u.h>
#include <libc.h>

char*    get9root(void)

char*    unsharp(char *path)

DESCRIPTION
This tree of Plan 9 software is conventionally installed in /usr/local/plan9 but may be installed in other places (for example, users without the ability to write to /usr/local may with to install it in their own home directories). The environment variable $PLAN9 should contain the path to the root. Get9root returns a static pointer to the pathname of root, first checking $PLAN9 and defaulting to /usr/local/plan9.

The lack of a fixed location for the Plan 9 tree makes it difficult to hard-code paths to files. Unsharp replaces a leading #9 in path with the root of the tree. Unsharp also replaces a leading #d with the path to the underlying system's file descriptor dup device, typically /dev/fd. The string returned from unsharp, if different from path, should be freed with free (see malloc(3)) when no longer needed.

As a convention, programs should never unsharp paths obtained from user input.

EXAMPLE
The plumber(4) uses this code to find unrooted file names included by plumb rules.

        snprint(buf, sizeof buf, "#9/plumb/%s", name);
        fd = open(unsharp(buf), OREAD);

SOURCE
/usr/local/plan9/src/lib9/get9root.c
/usr/local/plan9/src/lib9/unsharp.c

SEE ALSO
intro(4)

BUGS
Get9root could be smarter about finding the tree when $PLAN9 is not set.