History inside a Bash Loop

Question

I'm using bash to execute complex scripts having for and wile loops. I activate the history in the script using :

set -o history -o histexpand

But if I execute the following script:

#!/bin/bash
set -o history -o histexpand
for i in 1 2 3 4 5
do
   echo "Welcome $i times"
done
history

I can see that 'history' does not track commands inside the for loop :

[scripts]$ ~/test2.sh
Welcome 1 times
Welcome 2 times
Welcome 3 times
Welcome 4 times
Welcome 5 times
    1  for i in 1 2 3 4 5; do    echo "Welcome $i times"; done
    2  history

Is there a way to track the commands inside the for loop also ? In this present sample, I would love to get the following result :

[scripts]$ ~/test2.sh
Welcome 1 times
Welcome 2 times
Welcome 3 times
Welcome 4 times
Welcome 5 times
    1  for i in 1 2 3 4 5; do    echo "Welcome $i times"; done
    2  echo "Welcome $i times"
    3  echo "Welcome $i times"
    4  echo "Welcome $i times"
    5  echo "Welcome $i times"
    6  echo "Welcome $i times"
    7  history

May I know your concern for doing this. do you want to track your script flow while executing? — Siva
– Siva, Commented Sep 5, 2018 at 11:05
Of course : I would like to display the last executed command when there is an error, event if the error was inside a loop of my script... — Richard
– Richard, Commented Sep 5, 2018 at 12:38
Because I'm not in development phase anymore and the script is executed every 5 minutes. and I would like to send by e-mail a functional error report, displaying the command that did not work... And this command work certainly 99% of the time... — Richard
– Richard, Commented Sep 5, 2018 at 13:16

nst0022 · Accepted Answer · 2018-09-05 15:19:33Z

1

The "history" is a history of "previously typed" commands.

From the GNU manual:

"When the -o history option to the set builtin is enabled ... the shell provides access to the command history, the list of commands previously typed."

So, it does neither substitute shell variables, nor does it save loop iterations.

For this you could use bash debugging by calling your script so:

bash -x myscript > to-my-log-file

Then, in case of a crash, you can see what happened in the log file (provided the system had had time to flush the output buffer).

answered Sep 5, 2018 at 15:19

nst0022

4862 silver badges5 bronze badges

ok, thank you for your answer. It was also my first analysis, but I asked the question in case someone had a workaround...

Richard
– Richard

2018-09-05 17:45:10 +00:00
Commented Sep 5, 2018 at 17:45

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