how to continuously display a file of its last several lines of contents

Solution 1:

I use this function all the time to monitor a log file in another terminal window.

tail -f <filename>

I recommend taking it a step forward to look for particular text in the log. Great if you are only interested in seeing some particular entry being written to the file.

tail -f <filename> | grep <keyword or pattern>

Solution 2:

This will update every 2 seconds rather than whenever data is written to the file, but perhaps that's adequate:

watch 'head -n 2 job.sta; tail job.sta'

Solution 3:

You can use screen to simulate the expected behaviour:

1. Run screen, press Space.

2. Press Ctrl+a followed by S to split the screen.

3. Resize the top window by pressing Ctrl+a followed by :resize 4.

4. In the prompt in the top window, enter head -n2 file.

5. Move to the bottom window by pressing Ctrl+a followed by Tab.

6. Start a new screen session by pressing Ctrl+a followed by c.

7. In the new prompt, enter tail -f file.

Solution 4:

I use this script to achieve the effect you describe

!#/bin/bash
while [ 1 ]; do ls -lt data | head -n 30; sleep 3; echo -en "$(tput cuu 30; tput ed)"; done

This runs a command in a loop, and deletes the last lines of the output from the screen before each iteration.

In your case it would look something like

!#/bin/bash

while [ 1 ] ;# loop forever
do 
    head -n 2 job.sta ;# display first 2 lines 
    tail -n 30 job.sta ;# display last 30 lines from file
    sleep 3 ;# wait a bit
    echo -en "$(tput cuu 32; tput ed)" ;# delete last 32 lines from screen
done

Of course it is a bit ugly before your file reaches 30 lines

Hope that helps

Solution 5:

You want the multitail program, which not only does the split screen stuff but will also do color-coding.

http://www.vanheusden.com/multitail/