Golang为别人写的csv文件处理的例子

package main
import (
    "encoding/csv"
    "flag"
    "io"
    "log"
    "os"
    "sort"
    "strings"
)
var quick, first, unrepeat bool
func main() {
    path := flag.String("p", "", "-p 指定csv文件路径")
    logname := flag.String("l", "", "-l 指定结果输出路径,不指定则输出到标准输出")
    flag.BoolVar(&quick, "q", false, "-q 数据全部加载到内存中处理,默认是少量数据加载到内存操作,bool值")
    flag.BoolVar(&first, "f", false, "-f 使用首次遇到的一条数据,默认是使用最后遇到的一条数据,bool值")
    flag.BoolVar(&unrepeat, "u", false, "-u 默认是使用重复数据,bool值")
    flag.Parse()
    if *logname != "" {
        File, err := os.Create(*logname)
        if err != nil {
            log.Println("创建输出文件失败:", err.Error())
            return
        }
        log.SetOutput(File)
    }
    if *path == "" {
        flag.Usage()
        return
    }
    Read(*path)
}
func Read(path string) {
    File, err := os.Open(path)
    if err != nil {
        log.Println("读取csv文件失败,错误信息:", err.Error())
        return
    }
    defer File.Close()
    csvr := csv.NewReader(File)
    if quick {
        QMerge(csvr)
    } else {
        list := SMerge(csvr, File)
        FromLineRead(list, path)
    }
}
func QMerge(r *csv.Reader) {
    var m = make(map[string][]string)
    var list []string
    var repeat []string
    r.Read()
    var err error
    var key string
    for {
        list, err = r.Read()
        if err != nil {
            if err != io.EOF {
                log.Println("读取文件内容失败,错误信息:", err.Error())
            }
            break
        }
        if len(list) != 5 {
            log.Println("无效数据:", list)
            continue
        }
        key = strings.TrimSpace(list[1] + list[3])
        if key != "" {
            if _, ok := m[key]; ok {
                repeat = append(repeat, key)
                if !first {
                    m[key] = list
                }
            } else {
                m[key] = list
            }
        }
    }
    for _, value := range repeat {
        if unrepeat {
            delete(m, value)
        } else {
            log.Println(m[value])
        }
    }
    if unrepeat {
        for _, value := range m {
            log.Println(value)
        }
    }
}
func SMerge(r *csv.Reader, seek io.Seeker) []int {
    var m = make(map[string]int)
    var list []string
    var repeat []string
    r.Read()
    var key string
    var err error
    var line int
    for {
        list, err = r.Read()
        if err != nil {
            if err != io.EOF {
                log.Println("读取文件内容失败,错误信息:", err.Error())
            }
            break
        }
        if len(list) != 5 {
            log.Println("无效数据:", list)
            line++
            continue
        }
        key = strings.TrimSpace(list[1] + list[3])
        if key != "" {
            if _, ok := m[key]; ok {
                repeat = append(repeat, key)
                if !first {
                    m[key] = line
                }
            } else {
                m[key] = line
            }
        }
        line++
    }
    var lines = make([]int, 0, len(m))
    for _, v := range repeat {
        if unrepeat {
            delete(m, v)
        } else {
            lines = append(lines, m[v])
        }
    }
    if unrepeat {
        for _, v := range m {
            lines = append(lines, v)
        }
    }
    sort.Ints(lines)
    return lines
}
func FromLineRead(lines []int, path string) {
    File, err := os.Open(path)
    if err != nil {
        log.Println("读取csv文件失败:", err.Error())
        return
    }
    defer File.Close()
    r := csv.NewReader(File)
    r.Read()
    var list []string
    var line, index int
    for {
        list, err = r.Read()
        if err != nil {
            if err != io.EOF {
                log.Println("读取文件内容失败,错误信息:", err.Error())
            }
            break
        }
        if lines[index] == line {
            log.Println(list)
            index++
            if index >= len(lines) {
                break
            }
        }
        line++
    }
}