chmod(1) a+x
change file mode bits
The  format  of  a  symbolic  mode  is  [ugoa...][[+-=][perms...]...], where perms is either zero or more
letters from the set rwxXst, or a single letter from the set ugo.  Multiple symbolic modes can be  given,
separated by commas.

Change the mode of each FILE to MODE.
source manpages: chmod