chmod

Description

Attempts to change the mode of the file specified by filename to that given in mode.

Note that mode is not automatically assumed to be an octal value, so strings (such as "g+w") will not work properly. To ensure the expected operation, you need to prefix mode with a zero (0):

chmod ("/somedir/somefile", 755);   // decimal; probably incorrect   
chmod ("/somedir/somefile", "u+rwx,go+rx"); // string; incorrect       
chmod ("/somedir/somefile", 0755);  // octal; correct value of mode
      

Returns true on success and false otherwise.

See also chown() and chgrp().