mirror of https://github.com/GnoConsortium/gno.git
162 lines
4.0 KiB
Groff
162 lines
4.0 KiB
Groff
.\" Man page by Devin Reade.
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.\"
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.\" $Id: mapMode.3,v 1.2 1999/07/03 14:44:55 gdr-ftp Exp $
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.\"
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.TH MAPMODE 3 "14 December 1996" GNO "Library Routines"
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.SH NAME
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.BR _mapMode2GS ,
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.BR _mapMode2Unix ,
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.BR _getModeEmulation ,
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.BR _setModeEmulation
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\- (mapMode) perform mappings between Unix and GS/OS file permissions.
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.SH SYNOPSIS
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#include <sys/types.h>
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.br
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#include <gno/gno.h>
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.sp 1
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mode_t
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\fB_mapMode2GS\fR (mode_t \fImode\fR);
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.br
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mode_t
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\fB_mapMode2Unix\fR (mode_t \fImode\fR);
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.br
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int
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\fB_getModeEmulation\fR (void);
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.br
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int
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\fB_setModeEmulation\fR (int \fInewval\fR);
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.SH DESCRIPTION
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These routines are used to do mappings for file access bits between
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Unix and GS/OS file systems.
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.LP
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Under Unix, the lower nine bits of a
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.I mode
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are broken into groups of three. From most to least significant, these
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sets of three bits are used for User, Group, and Other permissions. Within
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each set, the bits refer to Read, Write, and Execute permissions.
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Under GS/OS, each file has associated with it bits for Read, Write, Invisible,
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Backup, Rename, and Destroy.
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.LP
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By default, the system calls
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.BR chmod (2),
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.BR creat (2),
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and
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.BR open (2)
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expect their mode parameters to be Unix modes. Before the underlying
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GS/OS toolset calls are made, these system calls therefore do mode mapping
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via the
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.BR _mapMode2GS
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call.
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(The system calls
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.BR fstat (2),
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.BR lstat (2),
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and
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.BR stat (2)
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.IR always
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return Unix modes in their
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.BR st_mode
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fields).
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.LP
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.BR _mapMode2GS
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takes a Unix
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.I mode
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parameter and maps it the GS/OS equivalent.
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If the User Read bit is set in
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.IR mode ,
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the Read bit will be set in the result. If the User Write bit is set in
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.IR mode ,
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all of the Write, Rename, and Destroy bits will be set in the result.
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Regardless of the value of
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.IR mode ,
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the Invisible bit is always cleared and the Backup bit is always set.
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.LP
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The reverse mapping may be achieved through
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.BR _mapMode2Unix .
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This function takes a GS/OS
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.I mode
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parameter and maps it the Unix equivalent.
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If the Read bit in
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.IR mode
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is set, then the User, Group, and Others Read bits in the result
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will be set. If all of the Write, Rename, and Destroy bits are set in
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.BR mode ,
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then the User, Group and Others Write bits will be set in the result.
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(If any of these three are cleared, the Write bits will not be set.)
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The result is bitwise
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.IR AND ed
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with the
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.BR umask (2)
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before
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.BR _mapMode2Unix
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returns the value. The high 7 bits (of 16) of the result are always cleared.
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.LP
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There are times when it may be desirable to disable the mappings done by
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.BR _mapMode2Unix
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and
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.BR _mapMode2GS .
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This functionality is achieved through the
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.BR _setModeEmulation
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function. If
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.IR newval
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is zero, the mode mapping is turned off; the mapping functions act as
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null ops. This implies that the mode parameters of the above system
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calls will be interpreted as GS/OS modes, (see the
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.BR CreatGS
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tool call in the
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.IR "GS/OS Reference Manual" ).
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.LP
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If a non-zero value is given for
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.IR newval ,
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the mode mapping functions are reactivated.
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.LP
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.BR _getModeEmulation
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allows the application programmer to determine whether or not the
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mapping functions are currently active.
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.SH COMPATIBILITY
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The Orca/C implementations of
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.BR chmod (2),
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.BR creat (2),
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and
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.BR open (2)
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expect GS/OS
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.IR mode
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values, which is the opposite of the default for this implementation.
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.LP
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.BR _getModeEmulation ,
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.BR _mapMode2Unix ,
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and
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.BR _mapMode2GS
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are thread safe.
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.BR _setModeEmulation
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is not.
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.SH "RETURN VALUE"
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.BR _getModeEmulation
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and
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.BR _setModeEmulation
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return the current or previous emulation value (zero or one), respectively.
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.LP
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.BR _mapMode2GS
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and
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.BR _mapMode2Unix
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return the appropriately mapped
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.IR mode
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or, if mapping has been disabled, the original value of
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.IR mode .
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.SH BUGS
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Since these routines don't known anything about file systems, nothing
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smart is done for permissions in an AppleShare environment.
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.LP
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The mappings performed by these routines are by their nature not
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entirely reversable.
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.SH AUTHOR
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Devin Reade <gdr@gno.org>
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.SH "SEE ALSO"
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.BR chmod (2),
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.BR creat (2),
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.BR open (2),
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.BR stat (2),
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.BR umask (2),
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.IR "The Apple IIgs GS/OS Reference" . |