Shell Programming and Scripting

I have a file in which "-"(by itself and nothing else) occurs in different fields in each record(sometimes in the 3 field, sometime in the 20th field, some time in the 100th field....etc). Also there are field of the format "abc-def". How do I replace fields that have just "-" with number zero. sed replaces all the "-", like "abc-def" would become "abc0def", I don't want that to happen.

What are the fields delimited by?

its a tab delimited file. I am trying to use gawk to replace the "-"

I've never used gawk, but sed can do the trick.

Code:

cat blah
abc-def -       ghi-jkl -       mno-pqr

sed 's/\t-\t/\t0\t/g' blah.dat > new_blah.dat

cat new_blah.dat
abc-def 0       ghi-jkl 0       mno-pqr

Thanks!!