touch - set modification date of a file

Touch will not touch directories.

                                                                                                   TOUCH(1plan9)

Touch  attempts  to  set the modification time of the files to time (by default, the current time).  If a
       file does not exist, it will be created unless option -c is present.

       touch - set modification date of a file

ls(1), stat(3), chmod(1)

/src/cmd/touch.c

touch [ -c ] [ -ttime ] file...