How to get programatically in the script the previous command input? [duplicate]

Question

I am looking at how to generically print in the Bash script the command input which has failed.

So instead of:

date -q || { echo "date -q"; return 1; }

I would like to have in my script something like

date -q || { echo !!; return 1; }

or

date -q || { fc -ln -1; return 1; }

Then, I can use compactly always the same code to print the command input which has failed in the script.

However, both attempts above, echo !! and fc -ln -1, do not solve the problem

For echo !! to work you'd need set -o history -o histexpand but it can't work on the same line because the whole line is a command, you'd have to use a condition with $? in a separate line — CherryDT
– CherryDT, Commented Jul 9, 2021 at 7:56
Thanks for the quick feedback! I was hoping there is some built-in functionality in Bash to achieve this goal, e.g. $_ retrieves the last word of previous command input. I am looking for the solution along the same lines, some built-in shortcut but for the whole previous command input, not only for the last word. — user9751447
– user9751447, Commented Jul 9, 2021 at 7:56
(messed up my previous edit) - you can save the command in a variable and run&echo it from there, using eval or better an array, see unix.stackexchange.com/a/444949/198262 — CherryDT
– CherryDT, Commented Jul 9, 2021 at 8:00
This will work, but then I have to use it for each single command input in the cript. The net result is that my script will get longer, nor shorter, as intended. — user9751447
– user9751447, Commented Jul 9, 2021 at 8:04

nino · Accepted Answer · 2021-07-09 09:36:43Z

0

What do you mean by command input? Do you want the script to print the literal command if it returns a non-zero exit status? If so, you can do this:

comm="date -q"
eval "$comm" || {
    echo "Failed command: $comm"
    return 1
}

If you want to do this on multiple commands:

## create an array of commands
commands=(
    "date -q"
    "date -w"
    "date -e"
    "date -r"
)

## iterate over the commands
for command in "${commands[@]}"; do
    eval "$command" 2>/dev/null || echo "Failed: $command"
done

edited Jul 9, 2021 at 9:36

answered Jul 9, 2021 at 8:03

nino

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3 Comments

user9751447 Over a year ago

Yes! Command and all its arguments. I seek an analogy to $_ which prints the last word of the previous command input, I just need something which prints the whole previous command input.

user9751447 Over a year ago

Thanks for the new post! This will work, but the problem if that I have to use it for each single command input in the script. The net result is that the script will get longer, and not shorter, as intended.

nino Over a year ago

So you'll need an array I guess. Have another look above.

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