BASH: how to view command history in while loop

bashlinuxshellshell-scriptUbuntu

I have a simple while loop accepting input:

#!/bin/bash
while true; do
    read -rep $'\n '"$USER"'> ' userInput
    echo "$userInput"
done

Example:

./input.sh 

 username> command1
command1

 username> command2
command2

Is it possible to have a command history? So that I can press up on my keyboard to view the previously executed commands (without leaving the while loop)?

Best Answer

You could use the small Readline wrapper rlwrap. This is a neat little tool that provides command history to utilities that don't implement it by themselves.

You would use rlwrap on the script itself:

rlwrap -a ./script.sh

This would save a history file called ~/.script.sh_history and would use that file not only in the current session, but also in future sessions to provide a sort of history that you could step through.

See the manual for rlwrap.

rlwrap is commonly available as a package on most Unices, but may also be had from its GitHub repository.

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SSH Shell Script – Why SSH Causes while Loop to Stop

SSH might be reading from standard input, eating up your actionlist. Try to redirect ssh's standard input to /dev/null:

ssh $REMOTE_HOST zfs snapshot -r ${RMT_FILESYSTEM}@${MARKER} </dev/null

As a general rule, when running commands that may interfere with standard input under a while read-style loop, I like to wrap the whole loop body into braces:

cat /tmp/uuoc | while read RMT_FILESYSTEM ISMOUNTED
do {
    echo ${RMT_FILESYSTEM}@${MARKER}
    [ "$ISMOUNTED" = "yes" ] && ssh $REMOTE_HOST zfs snapshot -r ${RMT_FILESYSTEM}@${MARKER}
    echo Remote Command Return Code: $?
} < /dev/null; done

Bash – How to retain cursor position in previous command

Maybe this is the option you're looking for?

history-preserve-point (Off)
        If  set to On, the history code attempts to place point at the
        same location on each history line retrieved 
        with previous-history or next-history.

To turn it on, add this to your ~/.inputrc:

set history-preserve-point on

Best Answer

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SSH Shell Script – Why SSH Causes while Loop to Stop

Bash – How to retain cursor position in previous command

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