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chmod (2)
  • chmod (1) ( Solaris man: Команды и прикладные программы пользовательского уровня )
  • chmod (1) ( FreeBSD man: Команды и прикладные программы пользовательского уровня )
  • chmod (1) ( Русские man: Команды и прикладные программы пользовательского уровня )
  • chmod (1) ( Linux man: Команды и прикладные программы пользовательского уровня )
  • chmod (1) ( POSIX man: Команды и прикладные программы пользовательского уровня )
  • chmod (2) ( Solaris man: Системные вызовы )
  • >> chmod (2) ( FreeBSD man: Системные вызовы )
  • chmod (2) ( Русские man: Системные вызовы )
  • chmod (2) ( Linux man: Системные вызовы )
  • chmod (3) ( Solaris man: Библиотечные вызовы )
  • chmod (3) ( POSIX man: Библиотечные вызовы )

  • BSD mandoc
     

    NAME

    
    
    chmod
    
     
    fchmod
    
     
    lchmod
    
     - change mode of file
    
     
    

    LIBRARY

    Lb libc
    
     
    

    SYNOPSIS

       #include <sys/stat.h>
    int chmod (const char *path mode_t mode);
    int fchmod (int fd mode_t mode);
    int lchmod (const char *path mode_t mode);
     

    DESCRIPTION

    The file permission bits of the file named specified by Fa path or referenced by the file descriptor Fa fd are changed to Fa mode . The chmod ();
    system call verifies that the process owner (user) either owns the file specified by Fa path (or Fa fd ) , or is the super-user. The chmod ();
    system call follows symbolic links to operate on the target of the link rather than the link itself.

    The lchmod ();
    system call is similar to chmod ();
    but does not follow symbolic links.

    A mode is created from or'd permission bit masks defined in In sys/stat.h :

    #define S_IRWXU 0000700    /* RWX mask for owner */
    #define S_IRUSR 0000400    /* R for owner */
    #define S_IWUSR 0000200    /* W for owner */
    #define S_IXUSR 0000100    /* X for owner */
    
    #define S_IRWXG 0000070    /* RWX mask for group */
    #define S_IRGRP 0000040    /* R for group */
    #define S_IWGRP 0000020    /* W for group */
    #define S_IXGRP 0000010    /* X for group */
    
    #define S_IRWXO 0000007    /* RWX mask for other */
    #define S_IROTH 0000004    /* R for other */
    #define S_IWOTH 0000002    /* W for other */
    #define S_IXOTH 0000001    /* X for other */
    
    #define S_ISUID 0004000    /* set user id on execution */
    #define S_ISGID 0002000    /* set group id on execution */
    #ifndef __BSD_VISIBLE
    #define S_ISTXT 0001000    /* sticky bit */
    #endif
    

    The Fx VM system totally ignores the sticky bit (ISTXT ) for executables. On UFS-based file systems (FFS, LFS) the sticky bit may only be set upon directories.

    If mode ISTXT (the `sticky bit') is set on a directory, an unprivileged user may not delete or rename files of other users in that directory. The sticky bit may be set by any user on a directory which the user owns or has appropriate permissions. For more details of the properties of the sticky bit, see sticky(8).

    If mode ISUID (set UID) is set on a directory, and the MNT_SUIDDIR option was used in the mount of the file system, then the owner of any new files and sub-directories created within this directory are set to be the same as the owner of that directory. If this function is enabled, new directories will inherit the bit from their parents. Execute bits are removed from the file, and it will not be given to root. This behavior does not change the requirements for the user to be allowed to write the file, but only the eventual owner after it has been created. Group inheritance is not affected.

    This feature is designed for use on fileservers serving PC users via ftp, SAMBA, or netatalk. It provides security holes for shell users and as such should not be used on shell machines, especially on home directories. This option requires the SUIDDIR option in the kernel to work. Only UFS file systems support this option. For more details of the suiddir mount option, see mount(8).

    Writing or changing the owner of a file turns off the set-user-id and set-group-id bits unless the user is the super-user. This makes the system somewhat more secure by protecting set-user-id (set-group-id) files from remaining set-user-id (set-group-id) if they are modified, at the expense of a degree of compatibility.  

    RETURN VALUES

    Rv -std  

    ERRORS

    The chmod ();
    system call will fail and the file mode will be unchanged if:

    Bq Er ENOTDIR
    A component of the path prefix is not a directory.
    Bq Er ENAMETOOLONG
    A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.
    Bq Er ENOENT
    The named file does not exist.
    Bq Er EACCES
    Search permission is denied for a component of the path prefix.
    Bq Er ELOOP
    Too many symbolic links were encountered in translating the pathname.
    Bq Er EPERM
    The effective user ID does not match the owner of the file and the effective user ID is not the super-user.
    Bq Er EPERM
    The effective user ID is not the super-user, the effective user ID do match the owner of the file, but the group ID of the file does not match the effective group ID nor one of the supplementary group IDs.
    Bq Er EPERM
    The named file has its immutable or append-only flag set, see the chflags(2) manual page for more information.
    Bq Er EROFS
    The named file resides on a read-only file system.
    Bq Er EFAULT
    The Fa path argument points outside the process's allocated address space.
    Bq Er EIO
    An I/O error occurred while reading from or writing to the file system.
    Bq Er EFTYPE
    The effective user ID is not the super-user, the mode includes the sticky bit ( S_ISVTX ) and path does not refer to a directory.

    The fchmod ();
    system call will fail if:

    Bq Er EBADF
    The descriptor is not valid.
    Bq Er EINVAL
    The Fa fd argument refers to a socket, not to a file.
    Bq Er EROFS
    The file resides on a read-only file system.
    Bq Er EIO
    An I/O error occurred while reading from or writing to the file system.

     

    SEE ALSO

    chmod(1), chflags(2), chown(2), open(2), stat(2), sticky(8)  

    STANDARDS

    The chmod ();
    system call is expected to conform to St -p1003.1-90 , except for the return of Er EFTYPE and the use of S_ISTXT  

    HISTORY

    The chmod ();
    function appeared in AT&T System v7 . The fchmod ();
    system call appeared in BSD 4.2 The lchmod ();
    system call appeared in Fx 3.0 .


     

    Index

    NAME
    LIBRARY
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    ERRORS
    SEE ALSO
    STANDARDS
    HISTORY


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