Struct and pointer sample

#include <stdio.h>

typedef struct Table Table;

struct Table {
        int Height;
        int  Width;
};

Table *  create_table(int height, int width)
{
    Table *mytable_ptr;

    Table my  = {height, width};

    mytable_ptr = &my;

    return mytable_ptr;

}



int main()
{
        Table  * my;
        my = create_table(10, 20);

       int height = my->Height;

       printf("h%d\n", height);
}

Enviorment variables

1. View all environment variables
export -p

2. View individual variables
echo $variable_name

3. Set variable dynamically
export APPLICATION_ENV='local'

4. Set variable permanently
put export statement in .profile

More MySql tips

dump db

mysqldump --host='127.0.0.1' --user=root --password='passwd' --column-statistics=0  db_name>dw.sql

redirect result to a csv file

select * from usermanager_users
 into outfile '/tmp/test.csv' fields terminated by ',' enclosed by '"' 
 lines terminated by '\n';

redirect result on command line

mysql -u [username ] -p[password] [db_name] -e " SELECT * FROM [tbl_name] " > file_name

Case sensitive compare

#Will match first name Mary, but not match mary
SELECT first_name FROM  `name` WHERE first_name  REGEXP BINARY 'Mary';

Show stored procedures

SHOW PROCEDURE STATUS WHERE Db = 'db_name'\G

# show details of procedure
SHOW CREATE PROCEDURE procedure_name\G

Create a mysql user

CREATE USER lshen@'10.18.276.170' IDENTIFIED   BY 'eikdkdk123scx';

select * from mysql.user where User="lshen"\G

GRANT SELECT  ON *.* TO lshen@'10.18.276.170';

FLUSH PRIVILEGES;

Query Cache

If swap between different MySQL versions, cache may cause problem. For example, they may use the different end character. Therefore, need to flush cache.

#To check whether the query cache is present in your MySQL server
mysql> SHOW VARIABLES LIKE 'have_query_cache';

#To monitor query cache performance
mysql> SHOW STATUS LIKE 'Qcache%';

#removes all query results from the query cache
mysql> RESET QUERY CACHE ;

Slove authentication method unknown to the client issue

Error message: Unable to open PDO connection [wrapped: SQLSTATE[HY000] [2054] The server requested authentication method unknown to the client.

root cause:This error is coming from MySQL 8.x’s new default auth‐plugin (caching_sha2_password) which older PHP/MySQL clients (PDO_MYSQL via mysqlnd) don’t yet understand.

source database server is using Mysql8.4. data warehouse is using php7.3

Solution: upgrade data warehouse to use PHP 8.0

<       apk add bash curl php7-mysqlnd php7-fileinfo php7-soap php7-pdo_mysql php7-xmlwriter mysql-client \
<        php7-dom php7-tokenizer msmtp gnu-libiconv ncurses util-linux && \
---
>        apk add bash curl php8-mysqlnd php8-fileinfo php8-soap php8-pdo_mysql php8-xmlwriter mysql-client mariadb-connector-c \
>        php8-dom php8-tokenizer msmtp gnu-libiconv ncurses util-linux && \

PHP cheating sheet

Cope File to Remote Server Using PHP

1. install php ssh2 extension

in ubuntu

apt-get install libssh2-1-dev libssh2-php

 test if php ssh2 installed

file_exists('ssh2_connect')

2. find finger print of remote server
 connect to the server
 ssh-keygen -lf /etc/ssh/ssh_host_rsa_key.pub
the second part is fingerprint

3. using ssh2 to scp files

$conn = ssh2_connect('remote-server-name', 22);

$fingerprint = ssh2_fingerprint($connection,
SSH2_FINGERPRINT_MD5 | SSH2_FINGERPRINT_HEX);

if ($fingerprint != $knowprint) {
    die("middle man found");
}
ssh2_auth_password($conn, 'username', 'password');

ssh2_scp_send($conn, 'file_name_in_local, 'file_name_in_remote', 0777);

Use call_user_func function

class Hello {
    public static function say_hello()
    {
        echo "Hello World!\n";
    }
}

//There are three ways to use call_user_func

//seperate class name and function
call_user_func(array("Hello", 'say_hello'));

//combine class name and function into one string
call_user_func('Hello::say_hello');

//create a object
call_user_func(array(new Hello(), 'say_hello'));

PHP extension

what extensions have been loaded

php -m 

In Alpine, extension is here /usr/lib/php/modules

Linux Commands

Limit resource a user can access

edit file /etc/security/limits.conf

//show limits
ulimit -a

See differences between two folders

diff -rq folder1 folder2

Find file in mac or Linux

find ./ -name platform_check.php

Open image

open test.png
open test.jpg

curl

//curl to redirect content to file
curl  --output leo.jpg https://checkout.whahaha-content.com/images/unionpay.png

created nested directories

The -p flag will create nested directories if directories do not exist. If exist, do nothing.

//mkdir: leo: No such file or directory
mkdir leo/test

//this works
mkdir -p leo/test

sed command

replace all occurences of a pattern

//ie flag will replace in place and that file will be modified
sed  -ie 's/unix/linux/g' my.txt

//all leo in my.txt will be replaced by developer. Also will make a backup file called my.txt.bak
sed -i.bak "s/leo/developer/g" my.txt

find which process is using a port number in mac

lsof -nP -iTCP -sTCP:LISTEN | grep <port-number>

In mac count items one level below current directory

find . -mindepth 1 -maxdepth 1 | wc -l

Configure dual monitor

In Ubuntu 12.04.1 LTS

Click Dash home, and type "display". Launch the display configure program.

In Window 7

Press window command key+p to launch the display configure program.

PhpStorm

Find usage for a function in the project

Select a symbol for which you want to find usages, right-click the symbol, and select Find Usages from its context menu.

Find functions in a file

View | Tool Windows | Structure

Variable type hint

/** @var RouteCollectorProxy $app */
    public static $app;

SVN Tip

SVN Patch

Run command in project root

1. Create a patch
svn diff > mypatch.diff

2. apply a patch
download patch

patch -p0 -i fix_path.diff

3. reverse patch
 patch -p0 -R -i fix_path.diff

4.  How to revert svn commit:
The following two commands will do the trick

svn merge -r 101:100 http://svn.example.com/repos/calc/trunk
svn ci



5. SVN Blame

svn blame svn://repositoy/filename
                       

Set up localhost server

1. npm init
2. npm install express
3. create a index.html and index.js
4. node index.js
5. http://localhost:5000

//index.js
const express = require('express');
const app = express();
const port = 5000;

app.get('/', (req, res) => {
    res.sendFile('index.html', {root: __dirname});
});

app.listen(port, () => {
    console.log(`Now listening on port ${port}`);
});

Create a post api using express

const express = require('express');
const app = express();

//middleware to parse incoming request with json payload
app.use(express.json());

//middleware to parse incoming request with url encoded payload
app.use(express.urlencoded({ extended: true }));

const port = 5000;

app.get('/', (req, res) => {
    res.sendFile('index.html', { root: __dirname });
});

app.listen(port, () => {
    console.log(`Now listening on port ${port}`);
});

app.post('/api/create_transaction', (req, res) => {
    const body = req.body;
    console.log("body:", body);
    res.status(201).json([]);
});

Change wireless password

1. connect a computer with router by cable
2. go to http://192.168.1.254
3. log in as admin
4. go to wireless ->security
5. change password

Propel Memo

Set up project

1. create database scheme xml from an existing database > propel-gen reverse
2. create model classes > propel-gen om
3. create config file > propel-gen convert-conf

Update Database

After database scheme XML is modified, we need to update database. Also need to generate model class again and running time conf

1. ../Propel/generator/bin/propel-gen sql
2. ../Propel/generator/bin/propel-gen insert-sql
3. ../Propel/generator/bin/propel-gen om
4. ../Propel/generator/bin/propel-gen convert-conf

MySql tips

Connect

#enter password manually
mysql --host='10.22.999.162' --user=leo --password

#password in command
mysql -h 10.49.41.213 -u leo --password='mysecret'

Show comments

1. Find table structure
> show columns from book;
> desc book;

get more details
> show create table book;

2 . Find table index
> show index from book;

3. Find permission of user
>  show grants;

show grants for 'cs_user'@'10.32.%.%' 

4. Find stored procedures
>  show procedure status

5. Find triggers
>  show triggers

6. Find more shows

More show commands

> help show;

Date time functions

 >  select date_format(convert_tz(from_unixtime(1370132292), "UTC", "America/Vancouver"), "%Y %m %d");

Stored Procedure

1. create procedure
drop procedure if exists countbook;

DELIMITER //

create procedure countbook()
BEGIN
    select count(*)
    from book;
END //

DELIMITER ;

2. call procedure
> call countbook() 

3. more notes
Stored procedure can take parameters. Parameters can be inputs or outputs. Inside procedure, can declare function (see ben forta MySql crash course)

More Store Procedure

 //find procedure
show procedure status where db="myDW"\G

//show procedure details
show create procedure load_dim_date\G

//flip that from security_type=definer to the invoker
ALTER PROCEDURE update_dim_date SQL SECURITY INVOKER;

More show process list

show full processlist
# 1234 is process id coming from show processlist
kill 1234

Find mysql server hostname

show variables where Variable_name = 'hostname';
+---------------+--------------------------------------+
| Variable_name | Value                                |
+---------------+--------------------------------------+
| hostname      | ip-10-32-210-21.corp.leotest.com |
+---------------+--------------------------------------+
1 row in set (0.09 sec)

Find mysql users

select * from mysql.user \G

Find mysql version

select version();

Update allowed ip for a user

# if version 5.7.8 and up, can use remame statement
RENAME USER 'qrhen'@'10.17.259.170' TO 'qrhen'@'10.31.248.110';

Grant permission to user

GRANT SELECT ON `MyTabble`.* TO `lyhen`@`10.33.264.%`;



FLUSH PRIVILEGES;

SHOW GRANTS FOR `lyhen`@`10.33.264.%`;

#show grants for current logged in user
show grants;

Check which process owns 3306

lsof -i :3306

jQuery cheat sheet

• parent()
• parents()
• closest() find the parent element nearest to the selected element
• children()
• siblings()
• prev()
• next()
• remove() $("p").remove() remove p elements
• empty() $("p").empty() delete content in ps
• detache() $elememts = $("p").detache() remove and hold
• replacewith()
• before()
• after()
• first()
• eq()
• last()
• slice()
• filter()
• not()

Create a SVN repository

Assume SVN server name is apple

1. ssh to  apple
svnadmin create /var/svn/project_name

2. go back to my machine, cd to  project_name/
svn import svn+ssh://apple/var/svn/project_name

3. check out

svn co svn+ssh://apple/var/svn/project_name

Regular Expression

Special Symbol
 \d is digit
\s is white space
. any char
\w equal [A-Za-z0-9_]


boundary
^ is start of string
$ is end of string
\b word boundary

how many times (for previous item)
?  0 or 1
* 0 or more
+ 1 or more
{n} n times
{n,} at least n times
{n,m} n<=match times<=m

group
(pattern) group as one item
(x|y) x or y
[abc] either a,b or c
[^abc] any char except a,b,c
[a-d] match a,b.c or d

PHP related function
preg_match("/mypatter/i", $subject) return 1 if match; otherwise, return 0.  i is a flag for case insensitive search.

Example

all combinations of digits chars and spaces  /^([a-zA-Z\d\s]+)+$/  For this regular expression, empty string will fail

Sample bashrc file

export CVS_RSH=ssh
export CVSROOT=:ext:cvs.somedomain.com:/var/cvs/cvsroot/php
export PATH=/homes/lshen/bin/:/usr/local/lib/jre1.6.0_22/bin/:/usr/bin/:/usr/bin/php/bin/:$PATH
export CLASSPATH=/usr/local/lib/jdk1.6.0_22/bin/:.
export JAVA_HOME=/usr/local/lib/jdk1.6.0_22/bin/
export EDITOR=/usr/bin/vim
export LC_CTYPE=en_US.UTF-8

xset b off

alias ls='ls --color=tty'
alias phpcs='phpcs --standard=Zend';
alias vi='vim'
alias lpr='lpr -P Ricoh'

Some useful command (Mysql Vi etc) Memo

My SQL

Grant a user to a database

mysql>grant all on db_name.* to 'db_username'@'localhost' identified by 'db_userpasswd'

dump a database to a sql file

mysqldump -u root -p --opt leo_db>dump.sql

vi

Auto replace string in vi

:%s/pattern_search_for/new_string_to_be_used/gc

Open and create compressed files

Open files

tar zxvf filename.tar.gz
unzip filename.zip
tar -xvf my.tar
bunzip2 studybuzz.bz2
bzip2 -d studybuzz.bz2
tar jxvf studybuzz.tar.bz2
unrar e test.rar

Create a zip file without parent directory

/test/test.txt
/test/test2.txt
cd test
zip -r -j my.zip *

Create files

zip -r filename.zip filedir
tar -cvf my.tar filedir

Print Env Variables

printenv

curl

curl -H "x-api-key:1234" http://myapi.com/user/1

#The -v option activates verbose mode, revealing detailed communication logs between the client and server
curl -v -H "x-api-key:1234" http://myapi.com/user/1

#curl does not follow HTTP redirects by default. Use the -L, --location option to tell it to do that
curl -L -H "x-api-key:1234" http://myapi.com/user/1