Read lines from text file in go, with bufio.reader

for {
	v, err = nextNum(reader, ' ')
	if err != nil {
		break
	}
	w, err = nextNum(reader, ' ')
	if err != nil {
		break
	}
	cost, err = nextNum(reader, '\n')
	if err != nil {
		break
	}
	fmt.Println(v, w, cost)
}

My text file consists of three coloumns and n rows. The first time nextNum is called the number in the first row and first column will be returned, next time the number in the second column and first row, and so on. My problem is when i get to the end and i call nextNum for the last time then i will recieve an EOF error and the last line will never get printed out, becuase break will be called before. Any suggestions on how to solve the problem?

CHeers

I guess there is no new line in the last row in your file and it's simply ending with EOF. It his correct? As a result, the very last column is not being parsed correctly, as it doesn't end with an expected character (\n).

You didn't show us exactly how you're using bufio.Reader, but either way you will need to account for missing new line at the end of file (it's up to you whether treat it as an error or not). Using methods like bufio.Reader.ReadString with \n delimiter won't treat EOF as the end-of-line automatically, but will return you a valid content along with EOF (i.e. you can get both data and error at the same call – note this is a different behaviour than in bufio.Reader.Read).

Saying this, it might be beneficial for you to use the csv package instead. It will solve the EOF problem and you could also benefit from some nicer error messages on unexpected number of columns. The additional features like comments or quotes might be good or bad for your purposes.

Example:

// No line break at the end, pure EOF (still works)
data := "one 1\ntwo 2\nthree 3\nfour 4"

// You can wrap your file reader with bufio.Reader here
cr := csv.NewReader(bytes.NewReader([]byte(data)))
cr.Comma = ' '
cr.FieldsPerRecord = 2

var err error
for err == nil {
	var columns []string
	if columns, err = cr.Read(); err == nil {
		fmt.Println(columns)
		// err = processRow(columns)
	}
}
if err != io.EOF {
	// Parse error
	panic(err)
}	

From the bufio docs:

> At EOF, the count will be zero and err will be io.EOF

So you can simply test for that. Like change your if err != nil to if err != nil && err != io.EOF

or

if err == io.EOF {
    fmt.Println(v, w, cost)
    break
}
if err != nil {
    break
}
fmt.Println(v, w, cost)

Though you really should do something with the error and not just ignore it.