Unexpected cut output

Question

I am getting an unexpected output from cut. I would expect no output since there is no third field based on the specified delimiter. The first two lines intentionally use commas as delimiters, and the third uses both commas and semicolons. I know how cut generally works, but I was trying to show that this shouldn't produce output in this example but it is.

input file: students.txt

Fred,Jones,sophomore
Mary,Adams,freshman
Sam,Fredrick;senior

cut command:

cut -f3 -d ';' students.txt

unexpected output:

Fred,Jones,sophomore
Mary,Adams,freshman

Answer 1

The reason why the lines, not containing the delimiter character, are printed can be found in the man page.

-f, --fields=LIST
       select only these fields; also print any line that contains no delimiter character,
                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
       unless the -s option is specified

and as @eyoung100 mentioned -s will not print them

-s, --only-delimited
      do not print lines not containing delimiters

Answer 2

Try:

cut -f 3 -d ';' -s students.txt

From the cut man page:

-s, --only-delimited

do not print lines not containing delimiters

I believe in this case s would stand for suppress.

Hint: This works because even though the comma is the delimiter, it isn't specified by the -d option.