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access(2)                        System Calls                        access(2)

       access, faccessat - determine accessibility of a file

       #include <unistd.h>
       #include <sys/fcntl.h>

       int access(const char *path, int amode);

       int faccessat(int fd, const char *path, int amode, int flag);

       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 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,

       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().

       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.

       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.

       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‐

       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

       See attributes(5) for descriptions of the following attributes:

       tab()   box;   cw(2.75i)  |cw(2.75i)  lw(2.75i)  |lw(2.75i)  ATTRIBUTE
       TYPEATTRIBUTE VALUE _ Interface StabilityCommitted _  MT-LevelAsync-
       Signal-Safe _ StandardSee below.

       For access(), see standards(5).

       Intro(2), chmod(2), stat(2), attributes(5), standards(5)

SunOS 5.11                        16 Jun 2009                        access(2)
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