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  Set file permission in Java

Prior to Java 6,  there is no good solution at the Java level to provide file permission management. You need to implement your own native methods or call the Runtime.exec() to invoke the system routine such as chmod in LInux. Since Java 6, Java introduces a set of methods which can be used to set the file permission at Java level. These methods include: File.setReadable(boolean); File.setWritable(boolean); FIle.setExecutable(boolean); File.setReadable(boolean, boolean); File.setWritable(bo...

   JAVA, FILE PERMISSION, POSIX,learnjava     2015-08-29 03:37:37

  How Kafka achieves high throughput low latency

Kafka is a message streaming system with high throughput and low latency. It is widely adopted in lots of big companies. A well configured Kafka cluster can achieve super high throughput with millions of concurrent writes. How Kafka can achieve this? This post will try to explain some technologies used by Kafka. Page cache + Disk sequential write Every time when Kafka receives a record, it will write it to disk file eventually. But if it writes to disk every time it receives a record, it would ...

   BIG DATA,KAFKA     2019-03-08 09:42:57

  Check file readability in Java

File operation is quite platform dependent. Although Java is a cross platform programming language, the file operation in Java is also platform dependent. The obvious evidence is the file permission check. In Java, we can call canRead(), canWrite() and canExecutable() to check whether the program can read, write or execute the file specified. However, on Windows, when we call canRead() on a File object, we may get unexpected result. Actually, on Windows, when we call canRead() on a File object, ...

   Java,Files,Readable,Check     2013-12-05 06:10:15

  Hide a file in a picture

Sometimes if you want to hide some important files on your computer which you don't want others to see, how would you do that? Find a professional tool? Set password for some folders? Change the file properties to hidden? They are possible, but they may not be so convenient or so secure. Here we share with you how to hide a file in a picture. Prerequisites 1 picture for example : test.jpg 1 test file, for example : test.txt WinRAR Steps Prepare the picture test.jpg and test file test.txt Use ...

   Trick,Picture,Fil hiding,WinRAR     2012-09-13 19:36:36

  Using MemoryMappedBuffer to handle large file in Java

When handling large files, it will largely affect the process speed while using traditional FileInputStream, FileOutputStream or RandomAccessFile since they trigger lots of read and write operations. In Java NIO, a new way of handling large file is introduced which is to use MmeoryMappedBuffer to create memory mapped file. Memory-mapped I/O uses the filesystem to establish a virtual memory mapping from user space directly to the applicable filesystem pages. With a memory-mapped file, you can pre...

   JAVA,IO,NIO     2015-11-13 01:58:08

  Fix issue docker-credential-desktop not installed or not available in PATH on Mac

Sometimes you may encounter below issue while running docker-compose on MacOS. Traceback (most recent call last): File "docker-compose", line 6, in <module> File "compose/cli/main.py", line 71, in main File "compose/cli/main.py", line 127, in perform_command File "compose/cli/main.py", line 1085, in up File "compose/cli/main.py", line 1081, in up File "compose/project.py", line 527, in up File "compose/service.py", line 354, in ensure_image_exists File "compose/service.py",...

   MACOS,DOCKER,DOCKER-COMPOSE     2020-06-23 03:25:16

  GoLang to build smaller executable file

Normally the executable file built with go is a bit large, it is always desired that a smaller executable file should be generated though. In this post, a couple of ways to reduce the size of the executable will be introduced. The end effect is that the executable file size would be much less than the normal generated one. The file which is built normally has below size. Mode LastWriteTime Length Name ---- ------------- ------ ---- -a---- 12/14...

   GOLANG,EXECUTABLE     2019-12-13 20:10:45

  How does PHP session work?

This article is about how PHP session works internally. Below are the steps : 1. Session in PHP is loaded into PHP core as an extension, we can understand it as an extension. When session extension is loaded, PHP will call core functions to get the session save_handler, i.e interface or functions for reading and writing session data. By default, PHP will handle session data by writing and reading files on the server. But PHP also supplies custom methods for handling session data, we can use sess...

   PHP, session, mechanism     2012-12-28 13:36:49

  Create temp file in Bash using mktemp and trap

When working on Linux Bash, sometimes there is need to create temporary file. A common way of creating temp file on Linux is creating some file in /tmp directory. However there is security risk when creating temp file in /tmp directory. This post will show how to securely create temp file in Linux Bash. When creating file in /tmp directory, there are some security risks. This directory can be accessed by any user on the system, any user can write data into this directory as well. The files creat...

   LINUX,MKTEMP,TRAP,TEMP FILE     2019-12-30 23:28:23

  Install flash plugin in Ubuntu

Step 1 : Get the libflashplayer.so file from Adobe offical websiteStep 2 : Extract the libflashplayer.so file to a folder Step 3 : Go tp the folder which sores the libflashplayer.so fileStep 4 : Run the following command in terminal             sudo ln -s libflashplayer.so /etc/alternatives/libflashplayer.soStep 5 : Start the Firefox and now can watch flash...

   Ubuntu,Flash,Install,Procedures,Plugin     2011-04-25 02:01:03

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