How to convert general JavaScript objects to json in Node.js? Assume jo is a JavaScript object, you can convert it to a json string by: JSON.stringify(jo)
Category: Tutorial
How to cut by multiple spaces in Linux?
Posted onHow to cut by multiple spaces in Linux? For example, if I get a string like a b c d where the spaces among the fields are not decided. How to get the four fields a, b, c and d out? Here, we take getting ‘b’ (the 2nd field) as the example. You can first
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How to install Chrome on Fedora Linux?
Posted onHow to install the Chrome browser on Fedora Linux from Google? Google provides a repository for yum/dnf on Fedora. First, following http://www.systutorials.com/3471/additional-repositories-for-fedora-linux/#google-chrome-repository to add Google Chrome repository. Then, you can install Google Chrome by yum/dnf: # dnf install google-chrome-stable
Auto Pressing Multiple Keys Together in Linux
Posted onThis post introduces a key presser on Linux with xvkb. But how to simulate pressing multiple keys together on Linux? That is, I would like to have multiple keys such as “A” “B” “C” “D” pressed together and being hold. How to simulate this on Linux with programs/commands? You can make use of xdotool (xdotool:
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How to send POST request in JavaScript?
Posted onHow to send POST request in JavaScript from the users’ browsers? One easy method I find is to use the jQuery library’s post() method. Here is one example that send POST request with data “file: filename” to the “/fileview” URL on the server and show the replied data: $.post(“/fileview”, {file: filename}, function (data) { //
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How to open a URL in a new window in JavaScript?
Posted onHow to open a URL in a new window in JavaScript? For example, to open a new window to browse “http://www.systutorials.com“. Open the URL in a new window: url = “http://www.systutorials.com”; window.open(url); Some browser will open the window in a new tab depending on the configuration. If you want to force the browser to open
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How to get file size in Python?
Posted onHow to get a file’s size in Python from the full path of a file? You can use this piece of Python code: os.path.getsize(file_path) It returns the size in bytes. It raises os.error if the file does not exist or is inaccessible. Manual of os.path.getsize(): https://docs.python.org/2/library/os.path.html#os.path.getsize
How to set the replication factor for one file when it is uploaded by `hdfs dfs -put` command line in HDFS?
Posted onWhen uploading a file by the hdfs dfs -put command line in HDFS, how to set a replication factor instead of the global one for that file? For example, HDFS’s global replication factor is 3. For some temporary files, I would like to save just one copy for faster uploading and saving disk space. The
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How to iterate all files and directories under a directory in Python?
Posted onHow to iterate all files and directories under a directory in Python? For example, I would like to iterate each file and directory under /mnt/data/ /mnt/data/ |– file.txt `– great That is: /mnt/data/files.txt /mnt/data/great You can use the os.walk to do this: root, dirs, files = os.walk(path).next() root will be the path.dirs will contain the
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How to get the file extension from a filename in Python?
Posted onHow to get the file extension from a filename in Python? For example, I would like to get “.txt” from “file.txt”. The Python code: >>> name, ext = os.path.splitext(‘file.txt’) >>> name ‘file’ >>> ext ‘.txt’ Manual of os.path.splitext: https://docs.python.org/2/library/os.path.html#os.path.splitext
How to parse POST data in node.js?
Posted onSome JavaScript libraries send data by POST instead of JSON. In node.js, how to parse the POST data? You can use the “querystring” module: var qs = require(‘querystring’) The following piece of code works well for me. The comments should help you read the code well. var post_handle = function(request, response) { if (request.method ==
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How to detect the #hash and get the hash in JavaScript?
Posted onHow to detect the #hash and get the hash in JavaScript? It’s better if no additional library is needed. That said, jquery is fine if it is needed. You can use this piece of JavaScript code: if (window.location.hash) { // hash found var hash = window.location.hash.substring(1); } else { // No hash }
How to exit the program in Node.js?
Posted onWhen fatal error happened, we’d like to kill the program. How to exit the program in Node.js? You can use: process.exit() Here, “process” is a global process object. exit method ends the process. process.exit([code]) Ends the process with the specified code. If omitted, exit uses the ‘success’ code 0. To exit with a ‘failure’ code:
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How to force ssh client to authenticate using password on Linux?
Posted onssh client can use many authentication methods like password, keys. On a server, I set password-less log in with private/public key. Now, I want to try whether the new password is set correctly by log on using ssh. By default, the key-based authentication method is used again. How to force ssh client to authenticate using
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How to detect whether Linux runs in UEFI or BIOS mode inside the Linux?
Posted onHow to detect whether Linux runs in UEFI or BIOS mode inside the Linux itself without needed to boot the the management console of the mother board? You can detect whether Linux runs in EFI mode by checking whether /sys/firmware/efi exist. In bash, you can test by [ -d /sys/firmware/efi/ ] This technique is used
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How to force a USB 3.0 port to work in USB 2.0 mode in Linux?
Posted onWe know that we can disable USB 3.0 in the BIOS. But is there a way to force a USB 3.0 port to work in USB 2.0 mode inside of a running Linux? On Linux on some platforms booted in BIOS modes, you can use the following command to force USB 2.0 modes for your
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How to make “tree” output consistent on Linux
Posted onI tried tree on different Linux boxes to verify the files by diff. However, I found the format can be a little bit different on different nodes. For examples, the tree result could be . |– test2 | |– test4 | `– test5 `– test3 1 directory, 3 files or . ├── test2 │  ├──
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Common SSD read/write throughput?
Posted onWhat is the common SSD read/write throughput on common SSDs? Following is a very brief test of the speed of a SSD that I have by hand: # time dd conv=fsync if=/dev/zero of=./test bs=8192 count=1048576 1048576+0 records in 1048576+0 records out 8589934592 bytes (8.6 GB) copied, 20.6098 s, 417 MB/s real 0m21.377s user 0m0.089s sys
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How to test whether the git repository is dirty?
Posted onHow to test whether the git repository is dirty? git status can show this. But how to diagrammatically detect this in bash? This piece of bash code works like a charm for me: [[ $(git diff –shortstat 2> /dev/null | tail -n1) != “” ]] You can use it to build your script. For example,
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How to get a FILE pointer from a file descriptor and how to get a file descriptor from a FILE pointer in C on Linux?
Posted onI would like to open files by open() directly. But how to get a FILE pointer from a file descriptor in C on Linux? And how to do the reverse direction: get a file descriptor from a FILE pointer? Get a FILE pointer from a file descriptor (e.g. fd) in C on Linux: FILE *file
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