In Ubuntu Linux, install the utility ffmpeg:
sudo apt-get install ffmpeg
Say you want to convert all the mp3 files in a directory to a single file called output.mp3. Then do the following.
1. cd to the directory
2. ls *.mp3 > list.txt
3. ffmpeg -f concat -i list.txt -c copy output.mp3
Tuesday, June 30, 2015
Sunday, June 28, 2015
Avoid shutdown or sleep when lid is close on Ubuntu Laptop
To avoid the Ubuntu laptop from shutting down when lid is closed, open the file '/etc/systemd/logind.conf' and add the following line at the bottom.
HandleLidSwitch=ignore
Then restart the following service:
sudo restart systemd-logind
HandleLidSwitch=ignore
Then restart the following service:
sudo restart systemd-logind
Tuesday, June 16, 2015
Date Command with Format
Date command in Linux shows the results as below:
#date
#Tue Jun 16 16:18:50 EDT 2015
But if you want to display the date say in the format 16-06-15 then use the following format option with date command:
#date +"%d-%m-%y"
#16-06-15
#date
#Tue Jun 16 16:18:50 EDT 2015
But if you want to display the date say in the format 16-06-15 then use the following format option with date command:
#date +"%d-%m-%y"
#16-06-15
Choose vi editor to open with crontab
Generally "crontab -e" opens with nano editor or gives an option to choose editor when opened for the first time.
If you want to change the editor later on, enter the command "select-editor" and choose vi. This will force crontab to use vi.
To find your ip address
To find your local IP address type the following command:
To find your global or internet ip address, type the following command:
- ip -o -f inet address show scope global|grep -Po "(?<=inet ).*(?=/)"
To find your global or internet ip address, type the following command:
- curl -w '\n' ident.me
- curl http://icanhazip.com
Thursday, June 4, 2015
Python Interpreter - Removing leading dots.
Create a .pythonrc.py file with following lines in the default home directory (~):
import sys
sys.ps1 = '>>'
sys.ps2 = ''
Add the following line in .bashrc or profile file to export variable.
export PYTHONSTARTUP="~/.pythonrc.py"
Wednesday, June 3, 2015
Use string variable or string to call a function
In python locals() return a dictionary representing the current local symbol table with all functions as dictionaries.
Say you have a function called "Func()". The locals() will return a dictionary with "Func" as shown below:
{....., 'Func': <function Func at 0x7f9ff50a5268>, ...........}
Now you can the call the function 'Func()' by the calling the dictionary key as below:
Direct String Substitution:
locals() ['Func'] ()
Variable Substitution:
F = "Func"
locals() ['F']
You can also use globals() instead of locals() if you need global system table.
If the function is part of a class then use getattr(class,"function")()
Say you have a function called "Func()". The locals() will return a dictionary with "Func" as shown below:
{....., 'Func': <function Func at 0x7f9ff50a5268>, ...........}
Now you can the call the function 'Func()' by the calling the dictionary key as below:
Direct String Substitution:
locals() ['Func'] ()
Variable Substitution:
F = "Func"
locals() ['F']
You can also use globals() instead of locals() if you need global system table.
If the function is part of a class then use getattr(class,"function")()
Monday, June 1, 2015
VIM HTML Documentation
How to Install and Launch VIM Documentation in HTML:
#1. First install the package vim-doc in your linux system.
#2. All the html files get installed at location /usr/share/doc/vim-doc/html/
#3. Open a browser and copy paste this link to get the main page.
file:///usr/share/doc/vim-doc/html/index.html
#1. First install the package vim-doc in your linux system.
#2. All the html files get installed at location /usr/share/doc/vim-doc/html/
#3. Open a browser and copy paste this link to get the main page.
file:///usr/share/doc/vim-doc/html/index.html
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