For example
grep -n 'integer*2' *.f
Shows nothing.But
grep -n '*2' *.f
main.f:57: integer*2 itime(nxmax)
main.f:605: dxy=((xsource(is)-xobs)**2+(ysource(is)-yobs)**2)**.5
main.f:622: chisum=chisum+diff2/uobs**2
model.f:15: integer*2 veli(nxmax)
model.f:52: size2=size**2
time.f:151: integer*2 itime(nxmax)
I really do not understand this.
* is an operator, meaning "match the previous term 0 or more times". So integer*2 matches
intege2
integer2
integerr2
integerrr2
:
none of which appear in your program. * at the beginning of an RE is meaningless (there's no previous term), so is either ignored or treated as match for a *. Escape the * to have it match an actual star:
'integer\*2'
Your grep is using a regex. (Star is being interpreted differently than you might believe). Try
grep -F -n 'integer*2' *.f
Because grep is interpreting the search argument as a regular expression, in which * is meant as "zero or more of the preceding". So 'integer*2 would match intege2 as well as integerrrrr2 since * applies to the preceding r but will not match the literal integer*2.
Escape it with a backslash to interpret it as a literal * and you should get the desired matches:
grep -n 'integer\*2' *.f
