mkdir.1posix -m 700 -p ~/.ssh
make directories
-m  mode
       Set the file permission bits of the newly-created directory to the specified mode value. The  mode
       option-argument  shall  be  the  same  as  the  mode operand defined for the chmod utility. In the
       symbolic_mode strings, the op characters '+' and '-' shall be interpreted relative to  an  assumed
       initial  mode  of  a=  rwx;  '+'  shall  add  permissions  to  the  default mode, '-' shall delete
       permissions from the default mode.
-p     Create any missing intermediate pathname components.
source manpages: mkdir