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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)
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