sed 批量替换 python to python2

sed -i 's/env python$/env python2/' *
	-i[SUFFIX], --in-place[=SUFFIX]
    	edit files in place (makes backup if SUFFIX supplied)
    s/regexp/replacement/
        Attempt  to  match  regexp  against the pattern space.  If successful, replace that portion matched with replacement. 
        The replacement may contain the special character & to refer to  that  portion  of  the  pattern space  which  matched,  and the special escapes 1 through 9 to refer to the corresponding matching sub expressions in the regexp.