System Calls access(2)
NAME
access, faccessat - determine accessibility of a file
SYNOPSIS
#include
#include
int access(const char *path, int amode);
int faccessat(int fd, const char *path, int amode, int flag);
DESCRIPTION
The access() function checks the file named by the pathname
pointed to by the path argument for accessibility according
to the bit pattern contained in amode, using the real user ID in place of the effective user ID and the real group ID in place of the effective group ID. This allows a setuid process to verify that the user running it would have hadpermission to access this file.
The value of amode is either the bitwise inclusive OR of theaccess permissions to be checked (R_OK, W_OK, X_OK) or the
existence test, F_OK.
These constants are defined inas follows: R_OK Test for read permission.
W_OK Test for write permission.
X_OK Test for execute or search permission.
F_OK Check existence of file
See Intro(2) for additional information about "File Access Permission".If any access permissions are to be checked, each will be
checked individually, as described in Intro(2). If the pro-
cess has appropriate privileges, an implementation may indi-
cate success for X_OK even if none of the execute file per-
mission bits are set.SunOS 5.11 Last change: 16 Jun 2009 1
System Calls access(2)
The faccessat() function is equivalent to the access() func-
tion, except in the case where path specifies a relativepath. In this case the file whose accessibility is to be
determined is located relative to the directory associated with the file descriptor fd instead of the current working directory.If faccessat() is passed in the fd parameter the special
value AT_FDCWD, defined in
directory is used and the behavior is identical to a call to, the current working access().
Values for flag are constructed by a bitwise-inclusive OR of
flags from the following list, defined in: AT_EACCESS The checks for accessibility are performed
using the effective user and group IDs instead of the real user and group ID as required in acall to access().
RETURN VALUES
If the requested access is permitted, access() and
faccessat()succeed and return 0. Otherwise, -1 is returned
and errno is set to indicate the error.ERRORS
The access() and faccessat() functions will fail if:
EACCES Permission bits of the file mode do not per-
mit the requested access, or search permis-
sion is denied on a component of the path prefix. EFAULT The path argument points to an illegal address.EINTR A signal was caught during the access()
function. ELOOP Too many symbolic links were encountered in resolving path, or loop exists in symbolic links encountered during resolution of the path argument.SunOS 5.11 Last change: 16 Jun 2009 2
System Calls access(2)
ENAMETOOLONG The length of the path argument exceeds
{PATH_MAX}, or a pathname component is
longer than {NAME_MAX} while _POSIX_NO_TRUNC
is in effect.ENOENT A component of path does not name an exist-
ing file or path is an empty string. ENOLINK The path argument points to a remote machine and the link to that machine is no longer active. ENOTDIR A component of the path prefix is not a directory. ENXIO The path argument points to a character or block device special file and the corresponding device has been retired by the fault management framework.EROFS Write access is requested for a file on a
read-only file system.
The faccessat() function will fail if:
EBADF The path argument does not specify an absolute pathand the fd argument is neither AT_FDCWD nor a valid
file descriptor open for reading or searching.The access() and faccessat() functions may fail if:
EINVAL The value of the amode argument is invalid.ENAMETOOLONG Pathname resolution of a symbolic link pro-
duced an intermediate result whose lengthexceeds {PATH_MAX}.
ETXTBSY Write access is requested for a pure pro-
cedure (shared text) file that is being exe-
cuted.SunOS 5.11 Last change: 16 Jun 2009 3
System Calls access(2)
The faccessat() function may fail if:
EINVAL The value of the flag argument is not valid. ENOTDIR The path argument is not an absolute path and fdis neither AT_FDCWD nor a file descriptor associ-
ated with a directory.USAGE
Additional values of amode other than the set defined in the description might be valid, for example, if a system hasextended access controls.
The purpose of the faccessat() function is to enable the
checking of the accessibility of files in directories other
than the current working directory without exposure to race conditions. Any part of the path of a file could be changedin parallel to a call to access(), resulting in unspecified
behavior. By opening a file descriptor for the target direc-
tory and using the faccessat() function, it can be
guaranteed that the file tested for accessibility is located
relative to the desired directory.ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
| MT-Level | Async-Signal-Safe |
|_____________________________|_____________________________|
| Standard | See below. ||_____________________________|_____________________________|
For access(), see standards(5).
SEE ALSO
Intro(2), chmod(2), stat(2), attributes(5), standards(5)SunOS 5.11 Last change: 16 Jun 2009 4