64 lines
1.3 KiB
Text
64 lines
1.3 KiB
Text
|
.TH ENV 3
|
||
|
|
.SH NAME
|
||
|
|
env \- environment variables
|
||
|
|
.SH SYNOPSIS
|
||
|
|
.nf
|
||
|
|
.B bind #e /env
|
||
|
|
|
||
|
|
.BI /env/ var1
|
||
|
|
.BI /env/ var2
|
||
|
|
...
|
||
|
|
.fi
|
||
|
|
.SH DESCRIPTION
|
||
|
|
The
|
||
|
|
.I env
|
||
|
|
device serves a one-level directory containing files with arbitrary names
|
||
|
|
and contents.
|
||
|
|
The intention is that the file name is the name of an
|
||
|
|
.I environment variable
|
||
|
|
(see
|
||
|
|
.IR rc (1)),
|
||
|
|
and the content is the variable's current value.
|
||
|
|
.PP
|
||
|
|
When a
|
||
|
|
.IR fork (2)
|
||
|
|
system call creates a new process, both the parent and the
|
||
|
|
child continue to see exactly the same files in the
|
||
|
|
.I env
|
||
|
|
device: changes made in either process can be noticed by the other.
|
||
|
|
In contrast, an
|
||
|
|
.B rfork
|
||
|
|
system call with the
|
||
|
|
.B RFENVG
|
||
|
|
bit set (see
|
||
|
|
.IR fork (2))
|
||
|
|
causes a split: initially both process groups see the
|
||
|
|
same environment files, but any changes made in one process group
|
||
|
|
cannot be noticed by the other.
|
||
|
|
An
|
||
|
|
.B rfork
|
||
|
|
with
|
||
|
|
.B RFCENVG
|
||
|
|
splits and then clears the environment.
|
||
|
|
.PP
|
||
|
|
The special global environment
|
||
|
|
.B #ec
|
||
|
|
contains kernel configuration variables,
|
||
|
|
such as those set in
|
||
|
|
.IR plan9.ini (8).
|
||
|
|
All processes see the same
|
||
|
|
.BR #ec ;
|
||
|
|
its contents are writable only by the host owner.
|
||
|
|
.SH SEE ALSO
|
||
|
|
.IR rc (1),
|
||
|
|
.IR fork (2),
|
||
|
|
.B #c/reboot
|
||
|
|
in
|
||
|
|
.IR cons (3),
|
||
|
|
.IR plan9.ini (8)
|
||
|
|
.SH SOURCE
|
||
|
|
.B /sys/src/9/port/devenv.c
|
||
|
|
.SH BUGS
|
||
|
|
A write starting at an offset after the current extent of a file
|
||
|
|
yields an error instead of zero filling.
|