V7/usr/man/man2/access.2

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.TH ACCESS 2 
.SH NAME
access \- determine accessibility of file
.SH SYNOPSIS
.B access(name, mode)
.br
.B char *name;
.SH DESCRIPTION
.I Access
checks the given
file
.I name
for accessibility according to
.I mode,
which is 4 (read), 2 (write) or 1 (execute) or a combination thereof.
Specifying mode 0
tests whether the directories leading to the file can be
searched and the file exists.
.PP
An appropriate error indication is returned if 
.I name
cannot be found or if any
of the desired access modes would not be granted.
On disallowed accesses
\-1 is returned and the error code is in
.IR errno .
0 is returned from successful tests.
.PP
The user and group IDs with respect to which permission is checked
are the real UID and GID of the process, so this call is
useful to set-UID programs.
.PP
Notice that it is only access bits that are checked.
A directory may be announced as writable by
.I access,
but an attempt to open it for writing will fail
(although files may be created there);
a file may look executable, but
.I exec
will fail unless it is in proper format.
.PP
.SH SEE ALSO
stat(2)
.SH ASSEMBLER
(access = 33.)
.br
.B sys access; name; mode