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