| 1 | .\" Copyright (c) 1980 Regents of the University of California.
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| 2 | .\" All rights reserved. The Berkeley software License Agreement
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| 3 | .\" specifies the terms and conditions for redistribution.
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| 4 | .\"
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| 5 | .\" @(#)access.2 6.5 (Berkeley) 5/22/86
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| 6 | .\"
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| 7 | .TH ACCESS 2 "May 22, 1986"
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| 8 | .UC 4
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| 9 | .SH NAME
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| 10 | access \- determine accessibility of file
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| 11 | .SH SYNOPSIS
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| 12 | .ft B
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| 13 | .nf
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| 14 | #include <sys/types.h>
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| 15 | #include <unistd.h>
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| 16 | .PP
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| 17 | .ft B
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| 18 | .ta 1.25i 1.6i
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| 19 | .nf
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| 20 | #define R_OK 4 /* test for read permission */
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| 21 | #define W_OK 2 /* test for write permission */
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| 22 | #define X_OK 1 /* test for execute (search) permission */
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| 23 | #define F_OK 0 /* test for presence of file */
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| 24 | .PP
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| 25 | .ft B
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| 26 | .nf
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| 27 | int access(const char *\fIpath\fP, mode_t \fImode\fP)
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| 28 | .ft R
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| 29 | .fi
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| 30 | .SH DESCRIPTION
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| 31 | .B Access
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| 32 | checks the given
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| 33 | file
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| 34 | .I path
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| 35 | for accessibility according to
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| 36 | .IR mode ,
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| 37 | which is an inclusive or of the bits
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| 38 | .BR R_OK ,
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| 39 | .BR W_OK
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| 40 | and
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| 41 | .BR X_OK .
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| 42 | Specifying
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| 43 | .I mode
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| 44 | as
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| 45 | .B F_OK
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| 46 | (i.e., 0)
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| 47 | tests whether the directories leading to the file can be
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| 48 | searched and the file exists.
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| 49 | .PP
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| 50 | The real user ID and the group access list
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| 51 | (including the real group ID) are
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| 52 | used in verifying permission, so this call
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| 53 | is useful to set-UID programs.
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| 54 | .PP
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| 55 | Notice that only access bits are checked.
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| 56 | A directory may be indicated as writable by
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| 57 | .BR access ,
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| 58 | but an attempt to open it for writing will fail
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| 59 | (although files may be created there);
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| 60 | a file may look executable, but
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| 61 | .B execve
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| 62 | will fail unless it is in proper format.
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| 63 | .SH "RETURN VALUE
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| 64 | If
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| 65 | .I path
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| 66 | cannot be found or if any of the desired access modes would
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| 67 | not be granted, then a \-1 value is returned; otherwise
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| 68 | a 0 value is returned.
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| 69 | .SH "ERRORS
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| 70 | Access to the file is denied if one or more of the following are true:
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| 71 | .TP 15
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| 72 | [ENOTDIR]
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| 73 | A component of the path prefix is not a directory.
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| 74 | .TP 15
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| 75 | [ENAMETOOLONG]
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| 76 | The path name exceeds PATH_MAX characters.
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| 77 | .TP 15
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| 78 | [ENOENT]
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| 79 | The named file does not exist.
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| 80 | .TP 15
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| 81 | [EACCES]
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| 82 | Search permission is denied for a component of the path prefix.
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| 83 | .TP 15
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| 84 | [ELOOP]
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| 85 | Too many symbolic links were encountered in translating the pathname.
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| 86 | (Minix-vmd)
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| 87 | .TP 15
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| 88 | [EROFS]
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| 89 | Write access is requested for a file on a read-only file system.
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| 90 | .TP 15
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| 91 | [EACCES]
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| 92 | Permission bits of the file mode do not permit the requested
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| 93 | access, or search permission is denied on a component of the
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| 94 | path prefix. The owner of a file has permission checked with
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| 95 | respect to the ``owner'' read, write, and execute mode bits,
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| 96 | members of the file's group other than the owner have permission
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| 97 | checked with respect to the ``group'' mode bits, and all
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| 98 | others have permissions checked with respect to the ``other''
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| 99 | mode bits.
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| 100 | .TP 15
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| 101 | [EFAULT]
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| 102 | .I Path
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| 103 | points outside the process's allocated address space.
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| 104 | .TP 15
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| 105 | [EIO]
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| 106 | An I/O error occurred while reading from or writing to the file system.
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| 107 | .SH "SEE ALSO
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| 108 | .BR chmod (2),
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| 109 | .BR stat (2).
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