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77 lines
1.5 KiB
Groff
77 lines
1.5 KiB
Groff
.TH GET9ROOT 3
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.SH NAME
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get9root, unsharp \- get path to root of Plan 9 tree
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.PP
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.B
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char* get9root(void)
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.PP
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.B
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char* unsharp(char *path)
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.SH DESCRIPTION
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This tree of Plan 9 software is conventionally installed in
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.B \*9
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but may be installed in other places (for example, users without
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the ability to write to
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.B /usr/local
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may with to install it in their own home directories).
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The environment variable
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.B $PLAN9
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should contain the path to the root.
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.I Get9root
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returns a static pointer to the pathname of root, first checking
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.B $PLAN9
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and defaulting to
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.BR \*9 .
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.PP
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The lack of a fixed location for the Plan 9 tree
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makes it difficult to hard-code paths
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to files.
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.I Unsharp
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replaces a leading
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.B #9
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in
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.I path
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with the root of the tree.
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.I Unsharp
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also replaces a leading
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.B #d
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with the path to the underlying system's file descriptor dup device,
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typically
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.BR /dev/fd .
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The string returned from
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.IR unsharp ,
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if different from
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.IR path ,
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should be freed with
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.I free
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(see
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.MR malloc (3) )
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when no longer needed.
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.PP
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As a convention, programs should never
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.I unsharp
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paths obtained from user input.
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.SH EXAMPLE
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The
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.MR plumber (4)
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uses this code to find unrooted file names included by plumb rules.
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.IP
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.EX
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snprint(buf, sizeof buf, "#9/plumb/%s", name);
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fd = open(unsharp(buf), OREAD);
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.EE
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.SH SOURCE
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.B \*9/src/lib9/get9root.c
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.br
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.B \*9/src/lib9/unsharp.c
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.SH SEE ALSO
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.MR intro (4)
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.SH BUGS
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.I Get9root
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could be smarter about finding the tree when
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.B $PLAN9
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is not set.
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