151 lines
4.1 KiB
Groff
151 lines
4.1 KiB
Groff
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.\" $NetBSD: setmode.3,v 1.21 2009/01/11 02:46:27 christos Exp $
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.\"
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.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)setmode.3 8.2 (Berkeley) 4/28/95
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.\"
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.Dd January 4, 2009
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.Dt SETMODE 3
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.Os
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.Sh NAME
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.Nm getmode ,
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.Nm setmode
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.Nd modify mode bits
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft void *
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.Fn setmode "const char *mode_str"
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.Ft mode_t
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.Fn getmode "const void *set" "mode_t mode"
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.Sh DESCRIPTION
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The
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.Fn setmode
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function accepts a string representation of a file mode change,
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compiles it to binary form, and returns an abstract representation
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that may be passed to
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.Fn getmode .
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The string may be an numeric (octal) or symbolic string of the form
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accepted by
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.Xr chmod 1 ,
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and may represent either an exact mode to set or a change to make to
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the existing mode.
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.Pp
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The
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.Fn getmode
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function
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adjusts the file permission bits given by
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.Fa mode
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according to the compiled change representation
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.Fa set ,
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and returns the adjusted mode.
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While only the permission bits are altered, other parts of the file
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mode, particularly the type, may be examined.
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.Pp
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Because some of the possible symbolic values are defined relative to
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the file creation mask,
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.Fn setmode
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may call
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.Xr umask 2 ,
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temporarily changing the mask.
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If this occurs, the file creation mask will be restored before
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.Fn setmode
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returns.
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If the calling program changes the value of its file creation mask
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after calling
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.Fn setmode ,
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.Fn setmode
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must be called again to recompile the mode string if
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.Fn getmode
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is to modify future file modes correctly.
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.Pp
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If the mode passed to
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.Fn setmode
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is invalid,
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.Fn setmode
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returns
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.Dv NULL .
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.Sh EXAMPLES
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The effects of the shell command
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.Ql "chmod a+x myscript.sh"
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can be duplicated as follows:
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.Bd -literal -offset indent
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const char *file = "myscript.sh";
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struct stat st;
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mode_t newmode;
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stat(file, \*[Am]st);
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newmode = getmode(setmode("a+x"), st.st_mode);
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chmod(file, newmode);
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.Ed
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.Sh ERRORS
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The
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.Fn setmode
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function
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may fail and set
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.Va errno
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for any of the errors specified for the library routines
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.Xr malloc 3
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or
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.Xr strtol 3 .
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In addition,
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.Fn setmode
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will fail and set
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.Va errno
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to:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa mode
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argument does not represent a valid mode.
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.El
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.Sh SEE ALSO
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.Xr chmod 1 ,
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.Xr stat 2 ,
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.Xr umask 2 ,
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.Xr malloc 3
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.Sh HISTORY
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The
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.Fn getmode
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and
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.Fn setmode
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functions first appeared in
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.Bx 4.4 .
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.Sh BUGS
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Each call to
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.Nm setmode
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allocates a small amount of memory that there is no correct way to
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free.
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.Pp
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The type of
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.Fa set
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should really be some opaque struct type used only by these functions
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rather than
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.Ft void * .
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