PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       fchmod — change mode of a file

SYNOPSIS

       #include <sys/stat.h>

       int fchmod(int fildes, mode_t mode);

DESCRIPTION

       The  fchmod()  function  shall  be  equivalent  to  chmod()  except  that  the  file whose
       permissions are changed is specified by the file descriptor fildes.

       If fildes references a shared memory object, the fchmod() function need  only  affect  the
       S_IRUSR, S_IWUSR, S_IRGRP, S_IWGRP, S_IROTH, and S_IWOTH file permission bits.

       If fildes references a typed memory object, the behavior of fchmod() is unspecified.

       If fildes refers to a socket, the behavior of fchmod() is unspecified.

       If  fildes  refers to a STREAM (which is fattach()-ed into the file system name space) the
       call returns successfully, doing nothing.

RETURN VALUE

       Upon successful completion, fchmod() shall return 0. Otherwise, it shall return -1 and set
       errno to indicate the error.

ERRORS

       The fchmod() function shall fail if:

       EBADF  The fildes argument is not an open file descriptor.

       EPERM  The effective user ID does not match the owner of the file and the process does not
              have appropriate privileges.

       EROFS  The file referred to by fildes resides on a read-only file system.

       The fchmod() function may fail if:

       EINTR  The fchmod() function was interrupted by a signal.

       EINVAL The value of the mode argument is invalid.

       EINVAL The fildes argument refers to a pipe and the implementation disallows execution  of
              fchmod() on a pipe.

       The following sections are informative.

EXAMPLES

   Changing the Current Permissions for a File
       The  following example shows how to change the permissions for a file named /home/cnd/mod1
       so that the owner and group have read/write/execute permissions, but the  world  only  has
       read/write permissions.

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

           mode_t mode;
           int    fildes;
           ...
           fildes = open("/home/cnd/mod1", O_RDWR);
           fchmod(fildes, S_IRWXU | S_IRWXG | S_IROTH | S_IWOTH);

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       chmod(),  chown(),  creat(),  fcntl(),  fstatat(),  fstatvfs(),  mknod(),  open(), read(),
       write()

       The Base Definitions volume of POSIX.1‐2017, <sys_stat.h>

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1-2017,  Standard  for  Information Technology -- Portable Operating System Interface
       (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C)  2018  by
       the  Institute  of  Electrical  and Electronics Engineers, Inc and The Open Group.  In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard,  the  original  IEEE  and  The  Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .