如果找不到grep，则打印破折号

Question

I would like this command to print a dash if grep not found (in addition to the new line already coded):

while read vl ; do grep -w "$vl" APL_vs_HS.tab || printf "\n" ; done < 1

Thanks! Bernardo

Answer 1

Why do you need to use printf ? Simply use echo , then you won't need to worry about printing a newline because echo automatically outputs one.

while read vl ; do grep -w "$vl" APL_vs_HS.tab || echo "-" ; done < 1

Answer 2

看到这个 ，这样就可以

while read vl; do grep -w "$vl" APL_vs_HS.tab || printf -- "-\n" ; done < 1