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("Change mode") The Unix command and systemcall to change the access permissions of a named file.Each file (directory, device, etc.) has nine kinds of accesswhich can be allowed or denied. Different permissions applyto the owner of the file, the members of the group the filebelongs to, and all users. Each of these classes of user(owner, group and other) can have permission to read, write orexecute the file. Chmod can also set various other mode bitsfor a file or directory such as the sticky bit and the setuser id bit.Unix man page: chmod