Editing a certain field on every line in a .csv file

Lets say I have a .csv (comma separated value) file looking like this:

Code:

---

123,1,"Abc",16.7
124,1,"Def",75.1
125,2,"Ghi",12.2
126,2,"Jkl",78.3
127,3,"Mno",12.3
128,4,"Pqr",84.9
129,4,"Stu",92.0

---

I want to find every line which has the number 4 in field 2, and change them to 7.
That would be these lines:

Code:

---

128,4,"Pqr",84.9
129,4,"Stu",92.0

---

Into this:

Code:

---

128,7,"Pqr",84.9
129,7,"Stu",92.0

---

I was thinking of searching for the first comma on each line, and checking if the number behind it is 4.
But with my very limited C++ knowledge I don't really know how.
Could anyone show me how to do this with comments to explain me what you did?

If anyone is interested, the reason I need this is for mass editing gamedata files that contains thousands of lines,
instead of opening them up in notepad and editing the lines manually one by one.

Thanks.

One way is to use getline and change the delimiter to ',' instead of the default which is a newline '\n'.

If you call that twice, then you'll get a string holding the second field. Convert that to an int with a stringstream (if necessary) and do your comparison and modification. Output everything as you read it in and just output the modified value for those cases where you are changing it.