A brief analysis of zip compression and zip decompression in Node (with code)

In the previous article "What you need to know about certbot to enable Amazon EC2 host https (code sharing)", we learned about certbot to enable Amazon EC2 host https. The following article will introduce you to zip compression and zip decompression in Node. Let's see how to do it.

##NodeJSFile (folder) compression/decompression scheme(zip/unzip)-Linuxon zipRelated commands

Use adm-zip

adm-zip supports one or more of archive and unarchive The function of a file or an entire folder is very simple and convenient to use.

var adm_zip = require("adm-zip");

//creating archives
var zip = new adm_zip();
zip.addLocalFolder("./dist");
zip.writeZip("./dist.zip");

//extracting archives
var unzip = new adm_zip("dist.zip");
unzip.extractAllTo("./dist", /*overwrite*/ true);

More apihttps://github.com/cthackers/adm-zip

Use JSZip

This library needs to be used when using Files are added to the

zip object one by one, and the content needs to be added manually, and then the file writing operation is used to convert the zip object in the memory into physical storage. So if it is for an entire folder, it is very troublesome. You need to traverse the folder

var JSZip = require("jszip");
var fs = require("fs");

var zip = new JSZip();

var file_content = fs.readFileSync("archive/a.txt");

zip.file("a.txt", file_content);

var data = fs.readFileSync("archive/img/pic.jpeg");
zip.file("img/pic.jpeg", data, { base64: true });

var zipfolder = zip.generate({ type: "nodebuffer" });

fs.writeFile("jszip.zip", zipfolder, function (err) {
  if (err) throw err;
});

JSZipThere is also a folder method, but it is only used Switch the virtual path inside the zip object, for example zip.folder("img").file('a.txt') is to add one in zip img subdirectory, create a.txt below, the effect is equivalent to zip.file("img/a.txt"). It should also be noted here that the contents of the file need to be added manually. If it is just zip.file("a.txt"); the content is just created in the zip object. An empty txt file, and it only exists in the memory and needs to be written to the file before it is actually saved to the disk.

More APIhttps://github.com/Stuk/jszip

Use archiver and unzip

archiverVery powerful , supports zip formattar format, you only need to provide the path to compress an existing folder.

Compression:

// require modules
var fs = require("fs");
var archiver = require("archiver");

// create a file to stream archive data to.
var output = fs.createWriteStream(__dirname + "/example.zip");
var archive = archiver("zip", {
  zlib: { level: 9 }, // Sets the compression level.
});

// pipe archive data to the file
archive.pipe(output);

// append a file from stream
var file1 = __dirname + "/file1.txt";
archive.append(fs.createReadStream(file1), { name: "file1.txt" });

// append a file from string
archive.append("string cheese!", { name: "file2.txt" });

// append a file from buffer
var buffer3 = Buffer.from("buff it!");
archive.append(buffer3, { name: "file3.txt" });

// append a file
archive.file("file1.txt", { name: "file4.txt" });

// append files from a sub-directory and naming it `new-subdir` within the archive
archive.directory("subdir/", "new-subdir");

// append files from a sub-directory, putting its contents at the root of archive
archive.directory("subdir/", false);

// append files from a glob pattern
archive.glob("subdir/*.txt");

// finalize the archive (ie we are done appending files but streams have to finish yet)
// 'close', 'end' or 'finish' may be fired right after calling this method so register to them beforehand
archive.finalize();

Decompression

var fs = require("fs");
var unzip = require("unzip");

fs.createReadStream("archiver-unzip.zip").pipe(
  unzip.Extract({ path: "unarchive" })
);

More APIhttps://github.com/archiverjs/node-archiver

zip/unzip command on Linux

apt-get install zip unzip

Unzip

zipFile

Syntax: unzip [-cflptuvz][-agcjlmnoqsvx][-P ][-x ] or unzip [-Z]

Additional instructions:

unzip Decompressor for .zip compressed files.

Parameters:

-cDisplay the decompression result on the screen and convert the characters appropriately.

-fUpdate existing files.

-lDisplay the files contained in the compressed file.

-p is similar to the -c parameter. It will display the decompression result on the screen, but will not perform any conversion.

-tCheck whether the compressed file is correct.

-u is similar to the -f parameter, but in addition to updating existing files, other files in the compressed file will also be decompressed into the directory.

-vDisplay detailed information when executing.

-zOnly display the comment text of the compressed file.

-aConvert the necessary characters to the text file.

-bDo not perform character conversion on text files.

-CFile names in compressed files are case-sensitive.

-jDo not process the original directory path in the compressed file.

-LChange all file names in the compressed file to lowercase.

-M Send the output results to the more program for processing.

-nDo not overwrite the original file when decompressing.

-oNo need to ask the user first, unzipoverwrites the original file after execution.

-P<Password> Use the password option of zip.

-qNo information is displayed during execution.

-sConvert whitespace characters in file names to underscore characters.

-VKeep the file version information of VMS.

-X When decompressing, the original UID/GID of the file will be saved at the same time.

[.zip file]Specify the .zip compressed file.

[File]Specify which files in the .zip compressed file are to be processed.

-dSpecify the directory where the file will be stored after decompression.

-xSpecifies which files in the .zip compressed file are not to be processed.

-Z unzip-Z is equivalent to executing the zipinfo command.

The basic usage is: zip [parameter][packaged file name] [packaged directory path]

Parameter:

-aConvert the file to ASCII mode

-FTry to repair the damaged compressed file

-hDisplay the help interface

-mAfter compressing the file, delete the source file

-n特定字符串 不压缩具有特定字尾字符串的文件

-o将压缩文件内的所有文件的最新变动时间设为压缩时候的时间

-q安静模式，在压缩的时候不显示指令的执行过程

-r将指定的目录下的所有子目录以及文件一起处理

-S包含系统文件和隐含文件（S 是大写）

范 例：

zip命令可以用来将文件压缩成为常用的zip格式。unzip命令则用来解压缩zip文件。 压缩文件abc.txt和一个目录dir1,名字test.zip：

zip -r test.zip abc.txt dir1
#解压缩：
```sh
unzip test.zip

目录下有abc1.zip，abc2.zip和abc3.zip，使用通配符

unzip abc\?.zip

注释：?表示一个字符，如果用*表示任意多个字符。 不解压，只查看内容

unzip -v test.zip

验证zip文件完成性,查看网上下的包包是不是已经下载完了

unzip -t test.zip

我用-v选项发现music.zip压缩文件里面有很多目录和子目录，并且子目录中其实都是歌曲mp3文件，我想把这些文件都下载到第一级目录，而不是一层一层建目录：

unzip -j music.zip

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