How to Use fs. readSync in node. js _ node. js-js tutorial

This article mainly introduces node. fs. readSync method usage instructions. This article introduces fs. readSync method description, syntax, receive parameters, use instances, and implement Source Code. For more information, see Method description:

Synchronous version of fs. read ().

Method returns a bytesRead (number of bytes read)

Syntax:

The Code is as follows:

Fs. readSync (fd, buffer, offset, length, position)

Because this method belongs to the fs module, we need to introduce the fs module (var fs = require ("fs") before use "))

Receiving parameters:

Fs

Buffer, data will be written.

Offset buffer write offset

Length (integer) specifies the length of the number of bytes that the file reads.

Position (integer) specifies the start position of File Reading. If this parameter is set to null, data is read from the current file pointer.

Example:

The Code is as follows:

Var fs = require ('fs ');
Fs.open('123.txt ', 'R', function (err, fd ){
If (err ){
Console. error (err );
Return;
}
Var buf = new Buffer (8 );
Var readfile = fs. readSync (fd, buf, 0, 8, null );
Console. log (readfile );
})

Source code:

The Code is as follows:

Fs. readSync = function (fd, buffer, offset, length, position ){
Var legacy = false;
If (! Util. isBuffer (buffer )){
// Legacy string interface (fd, length, position, encoding, callback)
Legacy = true;
Var encoding = arguments [3];
AssertEncoding (encoding );
Position = arguments [2];
Length = arguments [1];
Buffer = new Buffer (length );
Offset = 0;
}
Var r = binding. read (fd, buffer, offset, length, position );
If (! Legacy ){
Return r;
}
Var str = (r> 0 )? Buffer. toString (encoding, 0, r ):'';
Return [str, r];
};