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Rework the text to make it clearer; it was really pretty confusing before.

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Add an example; note some bugs/shortcomings. Bump date.
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dholland 2009-01-04 07:54:15 +00:00
parent 8f5f9030b6
commit 6557571403
1 changed files with 51 additions and 21 deletions
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72
lib/libc/gen/setmode.3
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@ -1,4 +1,4 @@
.\" $NetBSD: setmode.3,v 1.18 2005/10/01 20:08:01 christos Exp $
.\" $NetBSD: setmode.3,v 1.19 2009/01/04 07:54:15 dholland Exp $
.\"
.\" Copyright (c) 1989, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
@ -29,7 +29,7 @@
.\"
.\" @(#)setmode.3 8.2 (Berkeley) 4/28/95
.\"
.Dd October 1, 2005
.Dd January 4, 2009
.Dt SETMODE 3
.Os
.Sh NAME
@ -40,34 +40,40 @@
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft mode_t
.Fn getmode "const void *set" "mode_t mode"
.Ft void *
.Fn setmode "const char *mode_str"
.Ft mode_t
.Fn getmode "const void *set" "mode_t mode"
.Sh DESCRIPTION
The
.Fn setmode
function accepts a string representation of a file mode change,
compiles it to binary form, and returns an abstract representation
that may be passed to
.Fn getmode .
The string may be an numeric (octal) or symbolic string of the form
accepted by
.Xr chmod 1 ,
and may represent either an exact mode to set or a change to make to
the existing mode.
.Pp
The
.Fn getmode
function
returns a copy of the file permission bits
adjusts the file permission bits given by
.Fa mode
as altered by the values pointed to by
.Fa set .
While only the mode bits are altered, other parts of the file mode
may be examined.
according to the compiled change representation
.Fa set ,
and returns the adjusted mode.
While only the permission bits are altered, other parts of the file
mode, particularly the type, may be examined.
.Pp
The
.Fn setmode
function
takes an absolute (octal) or symbolic value, as described in
.Xr chmod 1 ,
as an argument
and returns a pointer to mode values to be supplied to
.Fn getmode .
Because some of the symbolic values are relative to the file
creation mask,
Because some of the possible symbolic values are defined relative to
the file creation mask,
.Fn setmode
may call
.Xr umask 2 .
.Xr umask 2 ,
temporarily changing the mask.
If this occurs, the file creation mask will be restored before
.Fn setmode
returns.
@ -75,7 +81,7 @@ If the calling program changes the value of its file creation mask
after calling
.Fn setmode ,
.Fn setmode
must be called again if
must be called again to recompile the mode string if
.Fn getmode
is to modify future file modes correctly.
.Pp
@ -85,6 +91,19 @@ is invalid,
.Fn setmode
returns
.Dv NULL .
.Sh EXAMPLES
The effects of the shell command
.Ql "chmod a+x myscript.sh"
can be duplicated as follows:
.Bd -literal -offset indent
const char *file = "myscript.sh";
struct stat st;
mode_t newmode;
stat(file, &st);
newmode = getmode(setmode("a+x"), st.st_mode);
chmod(file, newmode);
.Ed
.Sh ERRORS
The
.Fn setmode
@ -118,3 +137,14 @@ and
.Fn setmode
functions first appeared in
.Bx 4.4 .
.Sh BUGS
Each call to
.Nm setmode
allocates a small amount of memory that there is no correct way to
free.
.Pp
The type of
.Fa set
should really be some opaque struct type used only by these functions
rather than
.Ft void * .