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1.\" $NetBSD: access.2,v 1.7 1995/02/27 12:31:44 cgd Exp $
2.\"
3.\" Copyright (c) 1980, 1991, 1993
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33.\"
34.\" @(#)access.2 8.2 (Berkeley) 4/1/94
35.\"
36.Dd April 1, 1994
37.Dt ACCESS 2
38.Os BSD 4
39.Sh NAME
40.Nm access
41.Nd check access permissions of a file or pathname
42.Sh SYNOPSIS
43.Fd #include <unistd.h>
44.Ft int
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45.Fo access
46.Fa "const char *path"
47.Fa "int amode"
48.Fc
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49.Sh DESCRIPTION
50The
51.Fn access
52function checks the accessibility of the
53file named by
54.Fa path
55for the access permissions indicated by
2d21ac55 56.Fa amode .
9bccf70c 57The value of
2d21ac55 58.Fa amode
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59is the bitwise inclusive OR of the access permissions to be
60checked
61.Pf ( Dv R_OK
62for read permission,
63.Dv W_OK
64for write permission and
65.Dv X_OK
66for execute/search permission) or the existence test,
67.Dv F_OK .
68All components of the pathname
69.Fa path
70are checked for access permissions (including
71.Dv F_OK ) .
72.Pp
73The real user ID is used in place of the effective user ID
74and the real group access list
75(including the real group ID) are
76used in place of the effective ID for verifying permission.
77.Pp
78Even if a process has appropriate privileges and indicates success for
79.Dv X_OK ,
80the file may not actually have execute permission bits set.
81Likewise for
82.Dv R_OK
83and
84.Dv W_OK .
85.Sh RETURN VALUES
86If
87.Fa path
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88cannot be found
89or if any of the desired access modes would not be granted,
90then a -1 value is returned and the global integer variable
91.Va errno
92is set to indicate the error.
93Otherwise, a 0 value is returned.
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94.Sh ERRORS
95Access to the file is denied if:
96.Bl -tag -width Er
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97.\" ==========
98.It Bq Er EACCES
99Permission bits of the file mode do not permit the requested access,
100or search permission is denied on a component of the path prefix.
101.Pp
102The owner of a file has permission checked
103with respect to the ``owner'' read, write, and execute mode bits,
104members of the file's group other than the owner have permission checked
105with respect to the ``group'' mode bits,
106and all others have permissions checked
107with respect to the ``other'' mode bits.
108.\"
109.\" ==========
110.It Bq Er EFAULT
111.Fa Path
112points outside the process's allocated address space.
113.It Bq Er EINVAL
114An invalid value was specified for
115.Ar amode .
116.\" ==========
117.It Bq Er EIO
118An I/O error occurred while reading from or writing to the file system.
119.\" ==========
120.It Bq Er ELOOP
121Too many symbolic links were encountered in translating the pathname.
122.\" ==========
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123.It Bq Er ENAMETOOLONG
124A component of a pathname exceeded
125.Dv {NAME_MAX}
126characters, or an entire path name exceeded
127.Dv {PATH_MAX}
128characters.
2d21ac55 129.\" ==========
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130.It Bq Er ENOENT
131The named file does not exist.
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132.\" ==========
133.It Bq Er ENOTDIR
134A component of the path prefix is not a directory.
135.\" ==========
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136.It Bq Er EROFS
137Write access is requested for a file on a read-only file system.
2d21ac55 138.\" ==========
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139.It Bq Er ETXTBSY
140Write access is requested for a pure procedure (shared text)
2d21ac55 141file that is presently being executed.
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142.El
143.Sh SEE ALSO
144.Xr chmod 2 ,
145.Xr stat 2
146.Sh STANDARDS
147The
148.Fn access
149function conforms to
150.St -p1003.1-90 .
151.Sh CAVEAT
152.Fn Access
153is a potential security hole and
154should never be used.