access(2) DG/UX R4.11MU05 access(2)
NAME
access - determine the accessibility of a file
SYNOPSIS
#include <unistd.h>
int access const (path, amode)
const char * path;
int amode;
where:
path Address of a pathname naming a file of type ordinary,
directory, FIFO, block special, character special, or
symbolic link.
amode Access mode bit pattern
DESCRIPTION
Access checks that the calling process has specified access rights to
the file. If path refers to a symbolic link, the target of the
symbolic link is checked, not the symbolic link. The types of access
requested are indicated by amode, which can have the following
values:
F_OK
Check the existence of a file.
X_OK
Check for execute access. Applied to a directory, execute
permission allows the directory to be used in a pathname.
W_OK
Check for write access. Applied to a directory, write
permission allows the creation and deletion of links in the
directory.
R_OK
Check for read access. Applied to a directory, read
permission allows the contents of the directory to be listed.
EFF_ONLY_OK Check using the effective ID.
EXEC_OK Check for a regular executable file.
Some combination (logical OR) of X_OK, W_OK, and R_OK.
Write access is categorically denied when the file is of type
ordinary, directory, or FIFO and resides on a read-only file system
device. In this case, errno is set to EROFS.
In all other situations, a process with a real user id of 0 is
granted all access rights. Other processes are granted access only
if the file's mode gives them all types of access requested.
When determined by the file's mode, access is checked with respect to
only one of the owner, group, and other subsets of the mode. If the
process's real user id matches the file's user id, the owner bits of
the file mode determine access. If the process's real user id
doesn't match, but its real group id matches the file's group id or
one of the group ids in its group set matches the file's group id,
the group bits of the file mode determine access. In all other
cases, the 'other' mode bits determine access.
Note that this call does not guarantee that a file is writable or
executable if write or execute access is granted. For instance, a
directory's mode may give the caller write access, indicating that
files may be created in it, but an open of the directory for write
intent will fail.
ACCESS CONTROL
The caller must have permission to resolve path. This call differs
from others in that the process's real user id is used to determine
permission to resolve a pathname, rather than its effective user id.
RETURN VALUE
0 The requested access is permitted.
-1 Access to the file is denied. errno is set to
indicate the error.
DIAGNOSTICS
Errno may be set to one of the following error codes:
EACCES Permission bits of the file mode do not permit the
requested access or amode is invalid. Search
permissions are denied.
EROFS Write access is requested for a file of type ordinary,
directory, or FIFO that resides on a file system
device mounted read-only.
ENOENT The file the pathname resolved to does not exist.
ENOENT A non-terminal component of the pathname does not
exist.
ENOTDIR A non-terminal component of the pathname was not a
directory or symbolic link.
ENAMETOOLONG The pathname exceeds the length limit for pathnames.
ENAMETOOLONG A component of the pathname exceeds the length limit
for filenames.
ENOMEM There are not enough system resources to resolve the
pathname or to expand a symbolic link.
ELOOP The number of symbolic links encountered during
pathname resolution exceeded MAXSYMLINKS. A symbolic
link cycle is suspected.
EPERM The pathname contains a character not in the allowed
character set.
EFAULT The pathname does not completely reside in the
process's address space or the pathname does not
terminate in the process's address space.
SEE ALSO
chmod(2), fstat(2), stat(2), stat(5).
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