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access(2)
access(2) System Calls access(2)
NAME
access, euidaccess, faccessat - determine accessibility of a file
SYNOPSIS
#include <unistd.h>
#include <sys/fcntl.h>
int access(const char *path, int amode);
int euidaccess(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
had permission to access this file.
The euidaccess() is equivalent to the access() but uses the effective
user ID and the effective group ID.
The value of amode is either the bitwise inclusive OR of the access
permissions to be checked (R_OK, W_OK, X_OK) or the existence test,
F_OK.
These constants are defined in <unistd.h> as 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 indi‐
vidually, as described in Intro(2). If the process has appropriate
privileges, an implementation may indicate success for X_OK even if
none of the execute file permission bits are set.
The faccessat() function is equivalent to the access() function, except
in the case where path specifies a relative path. 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 <fcntl.h>, the current working directory is used
and the behavior is identical to a call to access().
Values for flag are constructed by a bitwise-inclusive OR of flags from
the following list, defined in <fcntl.h>:
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 a call to access().
RETURN VALUES
If the requested access is permitted, access(), euidaccess() and fac‐
cessat()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 permit the
requested access, or search permission 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 dur‐
ing resolution of the path argument.
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 existing 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 path and 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 produced an
intermediate result whose length exceeds {PATH_MAX}.
ETXTBSY Write access is requested for a pure procedure (shared
text) file that is being executed.
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 fd is neither
AT_FDCWD nor a file descriptor associated with a directory.
USAGE
Additional values of amode other than the set defined in the descrip‐
tion might be valid, for example, if a system has extended access con‐
trols.
The purpose of the faccessat() function is to enable the checking of
the accessibility of files in directories other than the current work‐
ing directory without exposure to race conditions. Any part of the path
of a file could be changed in parallel to a call to access(), resulting
in unspecified behavior. By opening a file descriptor for the target
directory 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(7) for descriptions of the following attributes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ Interface StabilityCommitted _ MT-LevelAsync-Signal-
Safe _ StandardSee below.
For access(), see standards(7).
SEE ALSO
chmod(2), Intro(2), stat(2), attributes(7), standards(7)
Oracle Solaris 11.4 22 Jan 2018 access(2)