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chmod()                COHERENT System Call               chmod()




Change file-protection modes

#include <sys/stat.h>
cchhmmoodd(_f_i_l_e, _m_o_d_e)
cchhaarr *_f_i_l_e; iinntt _m_o_d_e;

chmod sets the mode bits for file.  The mode bits include protec-
tion bits, the set-user-id bit, and the sticky bit.

mode is  constructed from the logical OR  of the following, which
are defined symbolically in the header file stat.h:


          04000  Set user identifier
          02000  Set group identifier
          01000  Save file on swap device (``sticky bit'')
          00400  Read permission for owner
          00200  Write permission for owner
          00100  Execute permission for owner
          00040  Read permission for members of owner's group
          00020  Write permission for members of owner's group
          00010  Execute permission for members of owner's group
          00004  Read permission for other users
          00002  Write permission for other users
          00001  Execute permission for other users


For directories,  some protection bits have  a different meaning:
write permission means  files may be created and removed, whereas
execute permission means that the directory may be searched.

The save-text  bit (or  ``sticky bit'') is  a flag to  the system
when it executes a shared for of a load module.  After the system
runs the program, it leaves shared segments on the swap device to
speed subsequent  reinvocation of the program.   Setting this bit
is  restricted to  the superuser  (to  control depletion  of swap
space which might result from overuse).

Only the owner of a file or the superuser may change its mode.

***** See Also *****

COHERENT system calls, creat()

***** Diagnostics *****

chmod returns  -1 for errors,  such as file  being nonexistent or
the invoker being neither the owner nor the superuser.








COHERENT Lexicon                                           Page 1

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