Ubuntu – How to cat file with limit of printed characters from each line

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.

Use head:

head -n1 -q *.txt > new-file

• -n1 tells head to extract the first line only.
• -q tells head not to print the filename.

On OS X (and probably on some other *nix variants) the -q option is not supported by head. You need to remove the filenames yourself, e.g.

head -n1 *.txt | grep -v '==> ' > new-file

This only works if you know the output shouldn't contain the ==>  string. To be absolutely sure, use a loop (which will be much slower than running head just once):

for file in *.txt ; do
    head -n1 "$file"
done