Scroll a shell script output without piping it into less

Question

I have a bash script.sh. I can easily scroll the output like this:

$ ./script.sh | less

But how do I make the output display scrollable automatically, without having to pipe it through less? In other words, how do I put that functionality right into the script itself? I just want to execute the script like this:

$ ./script.sh

I know I might be able to write a different script to execute the first one and pipe the output automatically but I don't want to have to write another script just to get the first one to do what I want it to do. Know what I mean?

that other guy · Accepted Answer · 2013-05-14 18:57:11Z

8

You can write your script like this:

#!/bin/bash
(

    Your script here

) | less
exit $PIPESTATUS

This will pipe the script output through less if output is a terminal (so you can ./script.sh > file without paging), and it preserves the script's exit code.

edited May 14, 2013 at 18:57

answered May 14, 2013 at 18:10

that other guy

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2 Comments

clt60 Over a year ago

less detects itself redirecting to file and stops paging. (at least on my system). Youre right with the exit code... ;)

that other guy Over a year ago

It checked whether stdout was a terminal, but as @jm666 points out, less handles that well by itself.

clt60 · Accepted Answer · 2013-05-14 18:13:07Z

4

Usually enough add the next into your script

#!/bin/bash

(  # add this to the start

#your old script here
date
cat /etc/passwd
df
ls -l
#end of your script

) | less      #and add this to the end

or you can put the whole script into a bash function like

#!/bin/bash

the_runner() {
#your old script here
date
cat /etc/passwd
df
ls -l
#end of your script
}
the_runner "$@" | less

answered May 14, 2013 at 18:13

clt60

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Comments

Mateusz Piotrowski · Accepted Answer · 2017-02-14 13:13:39Z

Instead of modifying the script itself I decided to add a special binding to Bash.

Effectively, you'll be able to write ./script.sh instead of ( ./script.sh ) | more.

Here's what you need to add to your .bashrc:

# Switch to vi mode (default is emacs mode).
set -o vi 
dont_scroll_down() {
    # Add the command to your history.
    history -s "$READLINE_LINE"
    # Redirect all output to less.
    bash -c "$READLINE_LINE" 2>&1 | less -eFXR
    # Remove the command from the prompt.
    READLINE_LINE=''
    # Optionally, you can call 'set -o vi' again here to enter
    # insert mode instead of normal mode after returning from 'less'.
    # set -o vi
}
bind -m vi -x '"J": "dont_scroll_down"'

As a result you'll be able to do the following thing:

Type in the command you want to run.
```
$ ./script.sh 
```
Hit Escape to exit insert mode and enter normal mode.
Now hit Shift-j to execute the line.

Now you should be able to scroll the output starting from the beginning.

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