mirror of https://github.com/GnoConsortium/gno.git
108 lines
3.8 KiB
Groff
108 lines
3.8 KiB
Groff
.\" Copyright (c) 1980, 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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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.\" @(#)umask.2 8.1 (Berkeley) 6/4/93
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.\"
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.\" .TH UMASK 2 GNO "System Calls" "14 December 1996"
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.TH UMASK 2 "14 December 1996" GNO "System Calls"
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.SH NAME
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.BR umask
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\- set file creation mode mask
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.SH SYNOPSIS
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.nf
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#include <sys/stat.h>
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mode_t umask (mode_t \fInumask\fR);
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.SH DESCRIPTION
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The
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.BR umask
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routine sets the process's file mode creation mask to
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.I numask
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and returns the previous value of the mask. The 9 low-order
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access permission
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bits of
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.I numask
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are used by system calls, including
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.BR open (2),
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.BR mkdir (2),
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and
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.BR mkfifo (2),
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to turn off corresponding bits
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requested in file mode.
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(See
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.BR chmod (2)).
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This clearing allows each user to restrict the default access
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to his files.
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.LP
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The default mask value is S_IWGRP|S_IWOTH (022, write access for the
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owner only).
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Child processes inherit the mask of the calling process.
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.LP
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Because the GNO kernel does not currently implement a mask, the mask
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value is maintained into child processes through the environment
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variable
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.BR UMASK ,
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which is assumed to be a string representing an octal mask value. For
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shells such as
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.BR gsh (1)
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which don't support a umask builtin command, the user's default mask may
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be controlled by setting the
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.BR UMASK
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environment variable.
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.SH RETURN VALUES
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The previous value of the file mode mask is returned by the call.
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.SH ERRORS
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The
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.BR umask
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function will never return an error condition, however it is possible
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that the
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.BR setenv (3)
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call used in the GNO implementation may fail. To detect this condition,
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the user must set
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.BR errno
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to zero prior to calling
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.BR umask ,
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and check it's value afterward. Under most circumstances this possible
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error condition may be ignored; the only side effect of
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.BR setenv
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failing in this case will be that the value of
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.I numask
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will not be maintained after an
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.BR execve (2).
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.SH SEE ALSO
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.BR chmod (2),
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.BR mknod (2),
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.BR open (2)
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.SH STANDARDS
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The
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.BR umask
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function call is expected to conform to IEEE Std 1003.1-1988 (POSIX).
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