60adc40118
Sometimes, there is the one-off occation when one needs to pass a huge list in rc... This change makes devenv track total memory consumption of environment groups allowing them to grow up to 1MB in size (including overhead). (Before, only the variable size was restricted, but not the amount of files being created). The maximum value size of a single environment variable is set to half of the total size, which allows the occational large value. (But not many of them). Because we track all memory consuption, it is also now possible to create around 10k small environment variales. A hashtable is added for name lookups and the qid.path was changed to allow direct indexing into the entry array without needing a scan lookup. All smalloc() calls have been removed, exhaustion is handled with error(Enomem) avoiding deadlock in case we run out of kernel memory.
60 lines
1.2 KiB
Text
60 lines
1.2 KiB
Text
.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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