Some nice #bash commands

#!/bin/bash

Make all files lower case in the folder in linux

for f in `find`; do mv -v "$f" "`echo $f | tr '[A-Z]' '[a-z]'`"; done

Rename all files in the directory sequentially

a=1
for i in *.mp4; do
  new=$(printf "%04d.mp4" "$a") #04 pad to length of 4
  mv -- "$i" "$new"
  let a=a+1
done

Check if variable null (not set) or not

  if [ -z "$var" ]
  then
    echo "\$var is empty"
  fi

Function definition

main ()
{
	echo "This is a function"
    # Use the passed parameter in the function.
    echo "Passed parameter is $1"
}

main "first parameter"

if-else conditionals

if [[ "$1" = "1" ]]; then
    echo "This is if"
elif [[ "$1" = "2" ]]; then
	echo "This is elif"
else
	echo "This is else"
fi

Format current date and time in a nicely

echo "Recent logs are at logs_`date +%Y%m%d_%H%M%S`"

Pipe both stderr and stdout to a file

python main.py 80 > logs_`date +%Y%m%d_%H%M%S` 2>&1 &