BASH: How to ask user input and store it for the future?

Question

I want to store a user message in a bash program, and then display the message the next time the user runs the script.

One way I thought this might work is if I export the message to an environmental variable, but I cannot get it to work.

Here is what I have so far, but it is not working:

echo "Last message was: $KEEPTHISMESSAGE"
echo "Type the new message that you want to enter, followed by [ENTER]:"
read KEEPTHISMESSAGE
export KEEPTHISMESSAGE

What am I doing wrong? If there is a better way to do this, please let me know. Maybe keep a file that keeps a history of these message and gets the most recent?

Related: stackoverflow.com/questions/226703/…

Jesse Nickles
– Jesse Nickles

2022-10-12 08:49:07 +00:00
Commented Oct 12, 2022 at 8:49 — Jesse Nickles
– Jesse Nickles, Commented Oct 12, 2022 at 8:49

Jim Garrison · Accepted Answer · 2011-09-19 23:50:00Z

7

You cannot use EXPORT this way. It only exports to processes started from within that invocation of the script. You must store the message in a file on the filesystem and load it in the next time your user executes the script. Very simply:

echo "Last message was: $(cat message.txt)"
echo "Type the new message that you want to enter, followed by [ENTER]:"
read KEEPTHISMESSAGE
echo $KEEPTHISMESSAGE > message.txt

You'll have to work out what happens the first time (when message.txt doesn't exist), and issues with relative/absolute paths to message.txt if you're running the script in a different directory.

answered Sep 19, 2011 at 23:50

Jim Garrison

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6 Comments

Usman Saleem Over a year ago

+1 This can be modified to use a hidden file (starts with a . ) Call it ~/.yourprog.history Read this file in your bash script by sourcing it, and overwrite the contents when your script ends.

Paul Over a year ago

echo $KEEPTHISMESSAGE > message.txt overwrites or creates message.txt ; Use >> for append

Eric Fortis Over a year ago

@Paul but appending is undesirable in his question, if he does that he should use tail -1 instead of cat

eric Over a year ago

@Jim and everyone else, thanks this was the solution. i also used >> for appending, and tail -1 instead of cat

f4m8 Over a year ago

'$ read -p "Type the new message that you want to enter, followed by [ENTER]:" KEEPTHISMESSAGE ' will do it in one step.

|

jman · Accepted Answer · 2011-09-19 23:52:10Z

2

Scripts can only directly export variables to their sub-processes. They can't export to parent processes.

You can alter a parents environment by invoking your script like this:

$ . /path/to/your_script.sh

Here your script should have an export statement to export the variable and must not have an exit statement.

answered Sep 19, 2011 at 23:52

jman

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