Commands are difficult to remember, and easy to forget, so here’s a common command repository

  • UPDATE pip packages 
      $ pip install --upgrade django-mailer==2.0.1
  # pip <command> <option> <package-name>==<version.number>
  • COPY file from one dir to another 
      $ cp -i path/to/file.py path/to/dir/
  # -i is for interactive, will be asked to replace any files
  • CREATE a directory with this date: 
      # create a directory with this date:
  $ mkdir "$(date '+%Y-%m-%d')"
  # dir name: 2020-03-10
  $ mkdir "$(date '+%Y-%m-%d--%H-%M-%S')"
  # dir name: 2020-03-10--11-03-01

  $ mkdir "$(TZ=UTC-8  date '+%Y-%m-%d--%H-%M-%S')"
  # dir name: 2020-03-10--13-10-59 (Beijing time)
  $ mkdir "$(TZ=UTC-0  date '+%Y-%m-%d--%H-%M-%S')"
  # dir name: 2020-03-10--05-11-05 (Greenwich time)
  • RSYNC a remote file to local through pipe 
      # rsync a remote file to local
  $ rsync -avz -e ssh user@ip_add:~/remote_dir/file local_dir/
  # '-e' is essential for creating an ssh connection
  • check mac environment variable 
      $ printenv

    check a specific variable

      $ echo $variable_name

    If setting more permanent environment variables:

    For system-wide operations, it should be in /etc/profile
    For user based operations, it should be in ~/.bash_profile
    For non-login interactive shells, it should be in ~/.bashrc
    For better understanding, you better check out this: Unix Introduction — Shell

  • Look for files: whereis 
      $ whereis python3
  /usr/bin/python3
  • locale 
      # check your locale setting
  $ locale
  # update it
  $ sudo update-locale LANG="en_US.UTF-8" LANGUAGE="en_US.UTF-8"
  • make nested dir 
      $ mkdir -p _backups/_archives

vim basic

输入：
i (insert, start editing)
: w filename （将文章以指定的文件名filename保存）
: wq (输入「wq」，存盘并退出vim)
: q! (输入q!， 不存盘强制退出vim)

The Many Uses of Rsync

It’s faster than scp (Secure Copy) because rsync uses remote-update protocol which allows to transfer just the differences between two sets of files. First time, it copies the whole content of a file or a directory from source to destination but from next time, it copies only the changed blocks and bytes to the destination. ```bash

basic format

$ rsync

$ rsync -av path/to/directory1/ /path/to/directory2/ $ rsync -av path/to/directory1 /path/to/directory2/

there’s a difference: copy the files in that folder or the folder itself

### **The flags/options**:
* -a: archive mode, archive mode allows copying files recursively and it also preserves symbolic links, file permissions, user & group ownerships and timestamps
* -v: As with many other commands, this option asks for verbose output. This is especially useful when copying large amounts of data.  
* -r : copies data recursively (but don’t preserve timestamps and permission while transferring data
* -z : compress file data
* -h : human-readable, output numbers in a human-readable format
* –delete: This flag isn’t used here but it is a common feature of rsync. This option deletes any files or folders in the destination that aren’t at the source. Use with extreme caution!
* -h or –help: This prints a help page that has useful information about using rsync.

### **zip, copy remotely, remove source files**
```bash
# use tar command to archive the files, django-archive is used to backup databases in my project
$ tar -zcvf backup1.tar.gz path/to/files/
# or create with a timestamp
$ tar -zcvf "$(date '+%y-%m-%d').tar.gz" path/to/files/

$ rsync -avz --remove-source-files path/to/backup1 user@ip_add:/path/to/backups/
# with a timestamp
$ rsync -avz --remove-source-files "$(date '+%y-%m-%d').tar.gz" user@ip_add:/path/to/backups/