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Can't replace CSV file content in Go

I created a csv file (assume "output.csv") using os.OpenFile

with flags, os.Create

and os.RDWR

. I am doing a series of operations on this file. In each iteration, I need to rewrite the content of the csv file ("output.csv"). But my code is being added to the csv file.

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2 answers


Before each rewriting, trim the file and look for the beginning. Example:



package main

import (
    "fmt"
    "os"
)

func main() {
    if f, err := os.Create("test.csv"); err == nil {
        defer f.Close()
        for n := 10; n > 0; n-- {
            f.Truncate(0) // comment or uncomment
            f.Seek(0, 0)  // these lines to see the difference
            for i := 0; i < n; i++ {
                f.WriteString(fmt.Sprintf("%d\n", i))
            }
        }
    } else {
        fmt.Println(err)
    }
}
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opening a file in read / write mode (os.RDWR) appended to the file.

Salt: open the file in read-only mode ( os.RDONLY ) to read and close it after reading.

csvfile ,_:= os.OpenFile("output.csv", os.O_RDONLY|os.O_CREATE, 0777)
csvfile.Close()


To write, open the file in write-only mode ( os.WRONLY ) and close it after writing, this will overwrite the file, not add.

csvfile ,_:= os.OpenFile("output.csv", os.O_WRONLY|os.O_CREATE, 0777)
csvfile.Close()

to add you can use os.APPEND

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