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- Bump document date for eaccess(2) addition.
- Mention ``eaccess'' in the NAME section. - Use intro(2) terminology. - Markup fixes. Reviewed by: rwatson
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2020-12-20 02:59:44 +00:00
svn path=/head/; revision=84805
@ -32,12 +32,12 @@
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.\" @(#)access.2 8.2 (Berkeley) 4/1/94
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.\" $FreeBSD$
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.\"
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.Dd April 1, 1994
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.Dd September 21, 2001
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.Dt ACCESS 2
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.Os
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.Sh NAME
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.Nm access
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.Nd check access permissions of a file or pathname
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.Nm access , eaccess
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.Nd check accessibility of a file
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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@ -53,35 +53,42 @@ and
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.Fn eaccess
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functions check the accessibility of the
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file named by
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the
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.Fa path
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argument
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for the access permissions indicated by
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.Fa mode .
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the
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.Fa mode
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argument.
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The value of
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.Fa mode
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is the bitwise inclusive OR of the access permissions to be
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is either the bitwise-inclusive OR of the access permissions to be
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checked
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.Pf ( Dv R_OK
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.Dv ( R_OK
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for read permission,
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.Dv W_OK
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for write permission and
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for write permission, and
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.Dv X_OK
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for execute/search permission) or the existence test,
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.Dv F_OK .
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for execute/search permission),
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or the existence test
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.Pq Dv F_OK .
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.Pp
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For additional information, see the
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.Dq File Access Permission
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.Sx "File Access Permission"
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section of
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.Xr intro 2 .
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.Pp
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The
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.Fn eaccess
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uses the effective user ID, group ID, and additional groups to authorize
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the request.
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call uses
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the effective user ID and the group access list
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to authorize the request;
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the
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.Fn access
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uses
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the real user ID in place of the effective user ID
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and the real group access list
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(including the real group ID) are
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used in place of the effective ID for verifying permission.
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call uses
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the real user ID in place of the effective user ID,
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the real group ID in place of the effective group ID,
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and the rest of the group access list.
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.Pp
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Even if a process's real or effective user has appropriate privileges
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and indicates success for
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@ -92,11 +99,7 @@ Likewise for
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and
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.Dv W_OK .
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.Sh RETURN VALUES
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If
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.Fa 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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.Rv -std
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.Sh ERRORS
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Access to the file is denied if:
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.Bl -tag -width Er
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@ -119,7 +122,7 @@ 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.
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.It Bq Er EFAULT
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.Fa Path
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.Fa path
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points outside the process's allocated address space.
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.It Bq Er EIO
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An I/O error occurred while reading from or writing to the file system.
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@ -134,14 +137,19 @@ The
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function call is expected to conform to
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.St -p1003.1-90 .
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.Sh CAVEAT
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.Fn Access
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The
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.Fn access
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call
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is a potential security hole due to race conditions and
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should never be used.
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Setuid and setgid applications should restore the effective uid or gid
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Set-user-ID and set-group-ID applications should restore the
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effective user or group ID,
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and perform actions directly rather than use
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.Fn access
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to simulate access checks for the real user of group id.
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.Fn Eaccess
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to simulate access checks for the real user or group ID.
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The
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.Fn eaccess
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call
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likewise may be subject to races if used inappropriately.
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.Sh HISTORY
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An
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