EUIDACCESS(3)             (2017-09-15)              EUIDACCESS(3)

     NAME
          euidaccess, eaccess - check effective user's permissions for
          a file

     SYNOPSIS
          #define _GNU_SOURCE             /* See feature_test_macros(7) */
          #include <unistd.h>

          int euidaccess(const char *pathname, int mode);
          int eaccess(const char *pathname, int mode);

     DESCRIPTION
          Like access(2), euidaccess() checks permissions and exis-
          tence of the file identified by its argument pathname. How-
          ever, whereas access(2) performs checks using the real user
          and group identifiers of the process, euidaccess() uses the
          effective identifiers.

          mode is a mask consisting of one or more of R_OK, W_OK,
          X_OK, and with the same meanings as for access(2).

          eaccess() is a synonym for euidaccess(), provided for com-
          patibility with some other systems.

     RETURN VALUE
          On success (all requested permissions granted), zero is
          returned.  On error (at least one bit in mode asked for a
          permission that is denied, or some other error occurred), -1
          is returned, and errno is set appropriately.

     ERRORS
          As for access(2).

     VERSIONS
          The eaccess() function was added to glibc in version 2.4.

     ATTRIBUTES
          For an explanation of the terms used in this section, see
          attributes(7).  allbox; lbw23 lb lb l l l.
          Interface Attribute Value T{ euidaccess(), eaccess()
          T}   Thread safety  MT-Safe

     CONFORMING TO
          These functions are nonstandard.  Some other systems have an
          eaccess() function.

     NOTES
          Warning: Using this function to check a process's permis-
          sions on a file before performing some operation based on
          that information leads to race conditions: the file

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     EUIDACCESS(3)             (2017-09-15)              EUIDACCESS(3)

          permissions may change between the two steps.  Generally, it
          is safer just to attempt the desired operation and handle
          any permission error that occurs.

          This function always dereferences symbolic links.  If you
          need to check the permissions on a symbolic link, use
          faccessat(2) with the flags AT_EACCESS and
          AT_SYMLINK_NOFOLLOW.

     SEE ALSO
          access(2), chmod(2), chown(2), faccessat(2), open(2),
          setgid(2), setuid(2), stat(2), credentials(7),
          path_resolution(7)

     COLOPHON
          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

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