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Just press the Ctrl and P keys together to fill the prompt with the last executed command and you are ready to go. This method works in bash perfectly even after closing the terminal, but it might not work in zsh after closing the session.
In bash for, while, and until are three loop constructs. While each loop differs syntactically and functionally their purpose is to iterate over a block of code when a certain expression is evaluated. Until loop is used to execute a block of code until the expression is evaluated to be false.
until passwd
do
echo "Try again"
done
or
while ! passwd
do
echo "Try again"
done
You need to test $? instead, which is the exit status of the previous command. passwd exits with 0 if everything worked ok, and non-zero if the passwd change failed (wrong password, password mismatch, etc...)
passwd
while [ $? -ne 0 ]; do
passwd
done
With your backtick version, you're comparing passwd's output, which would be stuff like Enter password and confirm password and the like.
To elaborate on @Marc B's answer,
$ passwd
$ while [ $? -ne 0 ]; do !!; done
Is nice way of doing the same thing that's not command specific.
If anyone looking to have retry limit:
max_retry=5
counter=0
until $command
do
sleep 1
[[ counter -eq $max_retry ]] && echo "Failed!" && exit 1
echo "Trying again. Try #$counter"
((counter++))
done
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