Shell – Run Same Linux Command in Multiple Tabs/Shells Simultaneously

You can do it in screen the terminal multiplexer.

• To split vertically: ctrla then |.
• To split horizontally: ctrla then S (uppercase 's').
• To unsplit: ctrla then Q (uppercase 'q').
• To switch from one to the other: ctrla then tab

Note: After splitting, you need to go into the new region and start a new session via ctrla then c before you can use that area.

EDIT, basic screen usage:

• New terminal: ctrla then c.
• Next terminal: ctrla then space.
• Previous terminal: ctrla then backspace.
• N'th terminal ctrla then [n]. (works for n∈{0,1…9})
• Switch between terminals using list: ctrla then " (useful when more than 10 terminals)
• Send ctrla to the underlying terminal ctrla then a.

(Convention - .txt are just plain text files. .sh files are shell script files.).

Your mainscript.txt script has a race condition. Specifically the while loop starts its next iteration before the script044.txt script is able to create the temporary file. In fact the whole loop is iterated through before any of these files get created.

A more robust way to deal with this sort of thing is to forget the temporary files and use the shell builtin wait instead:

#!/bin/bash

pid_count=0
for counter in $(seq 1 5)
do
    xterm -e "bash script044.txt" &
    if (( ++pid_count > 2 )); then
        wait -n
        ((pid_count--))
    fi
done

This increments a counter every time a subprocess is started. If the counter is greater than 3 then we wait for the next subprocess to finish. When wait returns, we then decrement the counter and go around again to start the next xterm.

You can remove all the tempfilename-related lines from the script044.txt - they are no longer needed.

As @chepner points out, the required -n option is only available in bash 4.3 or later.