.fp 5 CW

.de Af

.ds ;G \\*(;G\\f\\$1\\$3\\f\\$2

.if !\\$4 .Af \\$2 \\$1 "\\$4" "\\$5" "\\$6" "\\$7" "\\$8" "\\$9"

..

.de aF

.ie \\$3 .ft \\$1

.el \{\

.ds ;G \&

.nr ;G \\n(.f

.Af "\\$1" "\\$2" "\\$3" "\\$4" "\\$5" "\\$6" "\\$7" "\\$8" "\\$9"

\\*(;G

.ft \\n(;G \}

..

.de L

.aF 5 \\n(.f "\\$1" "\\$2" "\\$3" "\\$4" "\\$5" "\\$6" "\\$7"

..

.de LR

.aF 5 1 "\\$1" "\\$2" "\\$3" "\\$4" "\\$5" "\\$6" "\\$7"

..

.de RL

.aF 1 5 "\\$1" "\\$2" "\\$3" "\\$4" "\\$5" "\\$6" "\\$7"

..

.de EX \" start example

.ta 1i 2i 3i 4i 5i 6i

.PP

.RS

.PD 0

.ft 5

.nf

..

.de EE \" end example

.fi

.ft

.PD

.RE

.PP

..

.TH PREROOT 3

.SH NAME

preroot \- preroot support

.SH SYNOPSIS

.EX

#include <preroot.h>

char* getpreroot(char* \fIpath\fP, char* \fIcmd\fP);

int ispreroot(char* \fIdir\fP);

int realopen(char* \fIpath\fP, int \fImode\fP, int \fIperm\fP);

void setpreroot(char** \fIargv\fP, char* \fIdir\fP);

.EE

.SH DESCRIPTION

The

.I preroot

routines manipulate the process preroot.

.I preroot

is a kernel supported per-process two level viewpath.

All pathnames rooted at

.L /

are first searched for in the process preroot directory

and then in the system root directory.

Setting the process preroot is a priveleged operation controlled by the

.IR /etc/preroot (1)

command.

.PP

.L <preroot.h>

defines the symbol

.B FS_PREROOT

for those systems that support preroot.

The following routines are valid only when

.B FS_PREROOT

is defined:

.TP

.L getpreroot

returns a pointer to the absolute pathname of the preroot directory

for the executable

.IR cmd .

The result is placed in

.IR path .

If

.I path

is

.B 0

then

.IR malloc (3)

is used to allocate the pathname space.

.B 0

is returned if

.I cmd

has no preroot or if an error was encountered.

In this case

.I errno

is set to indicate the error.

.TP

.L ispreroot

Non-zero is returned if

.I dir

is the current process preroot.

If

.I dir

is

.B 0

then non-zero is returned if the current process has a preroot.

.TP

.L realopen

temporarily disables the process preroot and does an

.IR open (3)

relative to the system root directory.

The return value from

.I open

is returned.

If there is no preroot then

.I realopen

is equivalent to

.IR open .

.TP

.L setpreroot

calls

.IR execvp (3)

as

.L "execvp(a\fIrgv\fP[0],\fIargv\fP)"

with the process preroot set to

.IR dir .

.I argv

must be a

.BR 0 -terminated

argument array.

If

.I argv

is

.B 0

then the value of

.I opt_argv

from

.IR optget (3)

is used.

.L setpreroot

returns immediately if

.I dir

is already the process preroot.

.SH "SEE ALSO"

/etc/preroot(1)

.SH BUGS

Preroot semantics should be preserved when reading directories.

The

.I ast

.IR directory (3)

routines do this.

.IR 3d (1)

viewpathing does

.I preroot

the right way.