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Linux 2.6 - man page for fchmod (linux section 2)

CHMOD(2)			    Linux Programmer's Manual				 CHMOD(2)

       chmod, fchmod - change permissions of a file

       #include <sys/stat.h>

       int chmod(const char *path, mode_t mode);
       int fchmod(int fd, mode_t mode);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

	   || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L

       These  system calls change the permissions of a file.  They differ only in how the file is

       * chmod() changes the permissions of the file specified whose pathname is given	in  path,
	 which is dereferenced if it is a symbolic link.

       * fchmod() changes the permissions of the file referred to by the open file descriptor fd.

       The  new  file  permissions  are  specified  in mode, which is a bit mask created by ORing
       together zero or more of the following:

       S_ISUID	(04000)  set-user-ID (set process effective user ID on execve(2))

       S_ISGID	(02000)  set-group-ID (set process effective group  ID	on  execve(2);	mandatory
			 locking,  as  described in fcntl(2); take a new file's group from parent
			 directory, as described in chown(2) and mkdir(2))

       S_ISVTX	(01000)  sticky bit (restricted deletion flag, as described in unlink(2))

       S_IRUSR	(00400)  read by owner

       S_IWUSR	(00200)  write by owner

       S_IXUSR	(00100)  execute/search by owner ("search" applies  for  directories,  and  means
			 that entries within the directory can be accessed)

       S_IRGRP	(00040)  read by group

       S_IWGRP	(00020)  write by group

       S_IXGRP	(00010)  execute/search by group

       S_IROTH	(00004)  read by others

       S_IWOTH	(00002)  write by others

       S_IXOTH	(00001)  execute/search by others

       The  effective UID of the calling process must match the owner of the file, or the process
       must be privileged (Linux: it must have the CAP_FOWNER capability).

       If the calling process is not privileged (Linux: does not have the CAP_FSETID capability),
       and  the  group of the file does not match the effective group ID of the process or one of
       its supplementary group IDs, the S_ISGID bit will be turned off, but this will  not  cause
       an error to be returned.

       As  a security measure, depending on the filesystem, the set-user-ID and set-group-ID exe-
       cution bits may be turned off if a file is written.  (On Linux this occurs if the  writing
       process does not have the CAP_FSETID capability.)  On some filesystems, only the superuser
       can set the sticky bit, which may have a special meaning.  For the  sticky  bit,  and  for
       set-user-ID and set-group-ID bits on directories, see stat(2).

       On  NFS	filesystems,  restricting the permissions will immediately influence already open
       files, because the access control is done on the server, but open files are maintained  by
       the  client.   Widening	the  permissions  may  be  delayed for other clients if attribute
       caching is enabled on them.

       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

       Depending on the filesystem, other errors can be returned.  The more  general  errors  for
       chmod() are listed below:

       EACCES Search permission is denied on a component of the path prefix.  (See also path_res-

       EFAULT path points outside your accessible address space.

       EIO    An I/O error occurred.

       ELOOP  Too many symbolic links were encountered in resolving path.

	      path is too long.

       ENOENT The file does not exist.

       ENOMEM Insufficient kernel memory was available.

	      A component of the path prefix is not a directory.

       EPERM  The effective UID does not match the owner of the file,  and  the  process  is  not
	      privileged (Linux: it does not have the CAP_FOWNER capability).

       EROFS  The named file resides on a read-only filesystem.

       The general errors for fchmod() are listed below:

       EBADF  The file descriptor fd is not valid.

       EIO    See above.

       EPERM  See above.

       EROFS  See above.

       4.4BSD, SVr4, POSIX.1-2001.

       chown(2), execve(2), fchmodat(2), open(2), stat(2), path_resolution(7)

       This  page  is  part of release 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at

Linux					    2010-09-26					 CHMOD(2)

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