Ubuntu – How to display a random line from a text file

tr as you used it should work and is the simplest -- you just need to output to another file. If you use the input file as output, the result is an empty file as you observed;

cat myfile.txt | tr -d '\n' > oneline.txt

You need to remember some editors terminate a line with \r\n. For that case, use

cat myfile | tr -d '\r\n'

You can use sleep and clear commands in your script as following:

for word in $(< read)
do
    echo "$word"
    sleep 1
    clear
done

Explanation:

The sleep command make delay for a specified amount of time (in seconds). With sleep 1 delay would be for 1 second. You can change for more time delay by incrementing the second parameter or for delaying less than 1 second divide it to low units; Like sleep .1 for 1/10 second delay or sleep .001 for 1/1000 second delay and etc.

The clear command clear the terminal screen.

Even better you can do this through below awk command:

awk '{i=1; while(i<=NF){ print $((i++)); system("sleep 1; clear") }}' read

Explanation:

In awk, the NF specifies the total number of fields in the current input record/line, so by using a variable as a counter (i) and looping over it, we are printing all of them from 1st position to the end of them (NF). Then by using the system("sleep 1; clear") part, we are telling to awk to calling the system commands to sleeping for 1 second and clearing the screen.

In above we are displaying the input file as word by word. If you are going to display it line by line add IFS=$'\n' in the script like:

IFS=$'\n'
for word in $(< read)
do
    echo "$word"
    sleep 1
    clear
done

And change the awk command like:

awk '{ $0; system("sleep 1; clear") }1' read

• $0 specifies the current line. and the 1 on end enables the default awk's print command.