110 lines
2.7 KiB
Groff
110 lines
2.7 KiB
Groff
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.\" Copyright (c) 1980 Regents of the University of California.
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.\" All rights reserved. The Berkeley software License Agreement
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.\" specifies the terms and conditions for redistribution.
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.\"
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.\" @(#)access.2 6.5 (Berkeley) 5/22/86
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.\"
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.TH ACCESS 2 "May 22, 1986"
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.UC 4
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.SH NAME
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access \- determine accessibility of file
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.SH SYNOPSIS
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.ft B
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.nf
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#include <sys/types.h>
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#include <unistd.h>
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.PP
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.ft B
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.ta 1.25i 1.6i
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.nf
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#define R_OK 4 /* test for read permission */
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#define W_OK 2 /* test for write permission */
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#define X_OK 1 /* test for execute (search) permission */
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#define F_OK 0 /* test for presence of file */
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.PP
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.ft B
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.nf
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int access(const char *\fIpath\fP, mode_t \fImode\fP)
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.ft R
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.fi
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.SH DESCRIPTION
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.B Access
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checks the given
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file
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.I path
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for accessibility according to
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.IR mode ,
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which is an inclusive or of the bits
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.BR R_OK ,
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.BR W_OK
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and
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.BR X_OK .
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Specifying
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.I mode
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as
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.B F_OK
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(i.e., 0)
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tests whether the directories leading to the file can be
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searched and the file exists.
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.PP
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The real user ID and the group access list
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(including the real group ID) are
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used in verifying permission, so this call
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is useful to set-UID programs.
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.PP
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Notice that only access bits are checked.
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A directory may be indicated as writable by
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.BR access ,
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but an attempt to open it for writing will fail
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(although files may be created there);
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a file may look executable, but
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.B execve
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will fail unless it is in proper format.
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.SH "RETURN VALUE
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If
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.I path
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cannot be found or if any of the desired access modes would
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not be granted, then a \-1 value is returned; otherwise
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a 0 value is returned.
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.SH "ERRORS
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Access to the file is denied if one or more of the following are true:
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.TP 15
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[ENOTDIR]
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A component of the path prefix is not a directory.
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.TP 15
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[ENAMETOOLONG]
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The path name exceeds PATH_MAX characters.
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.TP 15
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[ENOENT]
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The named file does not exist.
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.TP 15
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[EACCES]
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Search permission is denied for a component of the path prefix.
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.TP 15
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[ELOOP]
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Too many symbolic links were encountered in translating the pathname.
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(Minix-vmd)
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.TP 15
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[EROFS]
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Write access is requested for a file on a read-only file system.
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.TP 15
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[EACCES]
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Permission bits of the file mode do not permit the requested
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access, or search permission is denied on a component of the
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path prefix. The owner of a file has permission checked with
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respect to the ``owner'' read, write, and execute mode bits,
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members of the file's group other than the owner have permission
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checked with respect to the ``group'' mode bits, and all
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others have permissions checked with respect to the ``other''
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mode bits.
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.TP 15
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[EFAULT]
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.I Path
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points outside the process's allocated address space.
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.TP 15
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[EIO]
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An I/O error occurred while reading from or writing to the file system.
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.SH "SEE ALSO
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.BR chmod (2),
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.BR stat (2).
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