![](/uploads/7868ce5a-2de0-4563-8082-8a47f296d46a.jpg)
package main
import(
"fmt"
"os"
"flag"
"io"
"io/ioutil"
"bufio"
"time"
)
// 使用os包,按照固定长度读取文件内容
func read1(path string)string{
fi,err := os.Open(path)
if err != nil{
panic(err)
}
defer fi. Close ()
chunks := make([]byte,1024,1024)
buf := make([]byte,1024)
for{
n,err := fi.Read(buf)
if err != nil && err != io.EOF{panic(err)}
if 0 ==n { break }
chunks=append(chunks,buf[:n]...)
// fmt.Println(string(buf[:n]))
}
return string(chunks)
}
// 使用os包+bufio包读取文件
func read2(path string)string{
fi,err := os.Open(path)
if err != nil{panic(err)}
defer fi.Close()
r := bufio.NewReader(fi)
chunks := make([]byte,1024,1024)
buf := make([]byte,1024)
for{
n,err := r.Read(buf)
if err != nil && err != io.EOF{panic(err)}
if 0 ==n {break}
chunks=append(chunks,buf[:n]...)
// fmt.Println(string(buf[:n]))
}
return string(chunks)
}
// 使用os包+ioutil包读文件
func read3(path string)string{
fi,err := os.Open(path)
if err != nil{panic(err)}
defer fi.Close()
fd,err := ioutil.ReadAll(fi)
// fmt.Println(string(fd))
return string(fd)
}
func main(){
flag.Parse()
file := flag.Arg(0)
f,err := ioutil.ReadFile(file)
if err != nil{
fmt.Printf("%s\n",err)
panic(err)
}
fmt.Println(string(f))
start := time.Now()
read1(file)
t1 := time.Now()
fmt.Printf("Cost time %v\n",t1.Sub(start))
read2(file)
t2 := time.Now()
fmt.Printf("Cost time %v\n",t2.Sub(t1))
read3(file)
t3 := time.Now()
fmt.Printf("Cost time %v\n",t3.Sub(t2))
}
运行命令go run read.go filename, 制定需要读取的文件就可以了。这里我比较了读取13.7MB的日志文件,三种方式分别消耗的时间是:
Cost time 105.006ms
Cost time 68.0039ms
Cost time 31.0018ms
读取29.3MB的媒体文件:
Cost time 390.0223ms
Cost time 194.0111ms
Cost time 83.0048ms
读取302MB的媒体文件
Cost time 40.8043338s
Cost time 1m5.0407201s
Cost time 8.8155043s
这个差距就很明显了,ioutil提供的方法效率就是高。下面我们从代码层面分析一下ioutil包