Golang interpretation (Go language) standard library analysis Io.ioutil

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Golang Standard Library

Today we are explaining the Io/ioutil package inside the Golang standard library – package io/ioutil
1. ioutil.ReadDir(dirname string)The prototype of this function is like this func ReadDir(dirname string) ([]os.FileInfo, error)
It is not difficult to see the input is the dirname type is a string type such as "D:/go", it will be a fileinfo slice, where the structure of FileInfo is like this
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Type FileInfo Interface {
Name () string//filename
Size () Int64//sang file sizes
Mode () FileMode//file permissions
Modtime () time. Time//Times
Isdir () bool//is the directory
Sys () interface{}//Basic data source interface (can return nil)
}
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So the returned slice can execute the FileInfo method, and what is the other parameter? Error is returned successfully! This time we can do the experiment code is such a demo
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Import "FMT"
Import "Io/ioutil"

Func Main () {
Dir_list, E: = Ioutil. ReadDir ("D:/test")
If E! = Nil {
Fmt. Println ("read dir error")
Return
}
For I, V: = Range Dir_list {
Fmt. Println (i, "=", V.name ())
Fmt. Println (V.name (), "Permission is:", V.mode ())
Fmt. Println (V.name (), "File Size:", v.size ())
Fmt. Println (V.name (), "Creation Time", V.modtime ())
Fmt. Println (V.name (), "System Information", V.sys ())
If v.isdir () = = true {
Fmt. Println (V.name (), "is Directory")

}
}
}
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2. The explanation is that the prototype of the ioutil.ReadFile(filename string) function isfunc ReadFile(filename string) ([]byte, error)
The input is a string type, which returns a byte-type slice and a err this is very simple we sit down code demo
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Import (
"FMT"
"Io/ioutil"
"OS"
)

Func Main () {
Data, err: = Ioutil. ReadFile ("D:/test/widua.go")
If err! = Nil {
Fmt. PRINTLN ("read error")
Os. Exit (1)
}
Fmt. Println (String (data))
}
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3. The third one we're explaining is that the prototype of the ioutil.ReadAll() function is func ReadAll(r io.Reader) ([]byte, error) an IO input. The reader meta-reader returns the []byte byte slice and error
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Import (
"FMT"
"Io/ioutil"
"Reflect"
"Strings"
)

Func Main () {
Reader: = strings. Newreader ("Hello word widuu")//Return to *strings. Reader
Fmt. Println (reflect. TypeOf (reader))
Data, _: = Ioutil. ReadAll (reader)
Fmt. Println (String (data))
}
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4. The fourth one is ioutil. The Nopcloser () function prototype is the Func nopcloser (r io. Reader) io. Readcloser is also a reader and then returns the Readcloser interface, which provides the Close method, the top method is perfect after the demo
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Import (
"FMT"
"Io/ioutil"
"Reflect"
"Strings"
)

Func Main () {
Reader: = strings. Newreader ("Hello word widuu")//Return to *strings. Reader
r: = Ioutil. Nopcloser (reader)
Defer R.close ()
Fmt. Println (reflect. TypeOf (reader))
Data, _: = Ioutil. ReadAll (reader)
Fmt. Println (String (data))
}
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5. The fifth is a common temporary directory ioutil.TempDir() function prototype is the func TempDir(dir, prefix string) (name string, err error) input directory name, prefix, return name is prefix+ random number
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Import (
"FMT"
"Io/ioutil"
)

Func Main () {
Dir, err: = Ioutil. TempDir ("D:/test", "tmp")
If err! = Nil {
Fmt. PRINTLN ("Common temp directory Failed")
Return
}
Fmt. Println (dir)//Return D:\test\tmp846626247 is the prefix+ random number in the front
}
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6. The last one, since you can create a directory, you can create ioutil.TempFile() a file function prototype is the func TempFile(dir, prefix string) (f *os.File, err error) input directory name, prefix, return the file pointer and error
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Import (
"FMT"
"Io/ioutil"
)

Func Main () {
File, Error: = Ioutil. Tempfile ("D:/test", "tmp")
Defer file. Close ()
If error! = Nil {
Fmt. Println ("Failed to create file")
Return
}
File. WriteString ("Hello word")//WriteString () Details of the file pointer are shown in the OS. WriteString ()
Filedata, _: = Ioutil. ReadFile (file. Name ())
Fmt. Println (String (filedata))
}
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