如何在unix中打印出包含特定String的文件的所有行

Question

I know how to print out the line of the first occurrence of the String but I'm not sure how to print out all occurrences. To print out the first occurrence of my String I have used

grep ",1," my_course.

I feel like printing out all occurrences would look something like:

    while(file has next line)
         grep ",1," my_course

I'm not sure how to do this while loop though. How do I test if file has next line.

EDIT: Sorry guys I thought grep only matched the first occurrence. When I ran it, it only matched 1 line. I didn't know only 1 line matched

Also, bonus question if someone wants to answer... if all the lines in my file (my_course) look like "number,name,credit hours,grade" how would I get all the grades in the file and store into an array?

Answer 1

grep already prints out all occurrences.

From the man pages of grep:

grep, egrep, fgrep - print lines matching a pattern