how to use ctrl-D in a shell script

I have a bash shell script that requires ctrl-D to break out of the terminal.can anyone tell me how to use it in the shell script

example

ssh host last --->displays the list of users who were logged on to that host

I have different hosts the output is appended to one final and when I'm executing this particular shell script along with other 开发者_Go百科series of commands, i'm using ctrl-D to see the output

suppose my shell script is myscript.sh to execute myscript.sh

./myscript.sh

ctl-D

connection to host closed

output is displayed

Instead, I want to use ctrl-D in my script file

There is no way to do this directly. Use a heredoc to feed stdin instead.

./someprog.sh << EOF
something here
EOF

You could try exec <&-
&- is used to close a file descriptor (ps:everything in linux is a kind of file...)
<&- is closing file descriptor 0 = stdin - can also be written as 0<&-

If you open a normal terminal in your linux machine and type exec <&- you will see your terminal to close/dissapear like if you press ^D.

PS1: Similarly, exec >&- closes stdout

PS2: If you close stdin with exec <&- you can re-open to continue your script with something like exec </dev/tty

To detect Ctrl-D in scripts and run custom logic on it you can read input char by char and check if char key code corresponds to Ctrl-D.

Here is a code example:

IFS=
while true; do
    read -n 1 key
    line=$line$key
    printf -v key_code "%d" "'$key"
    if [ $key_code -eq 4 ]; then
        echo "Ctrl-D pressed!"
    fi
    if [ "$key" = '' ]; then
        echo "Line was $line"
        line=
    fi
done

Use this

read  Input
#When ^D is used, read ends up with the exit code "1"
if [[ $? == 1 ]]
then 
     echo "[Ctrl+D] is captured"
fi

#! /bin/sh
echo 'Enter one line at a time'
echo 'Press CTRL+D to finish'
cat >test.out
echo 'OK'

Why don't you tell last how many lines you want to see? Then you won't have to interrupt it with a Ctrl+D. For example, to see 10 lines use:

ssh hostname "last -10"