Persistent variable

Shell Programming and Scripting
1

I found a way to make a numeric variable persistent for a script :

#!/bin/bash
function Persist()    {    # 1:Expression like VARIABLE=Value (numeric)
    local V=${1%=*}
    eval "$1"
    sed -i "s/^$V=[0-9][0-9]*/$1/" $(which $(basename $0)) || return 1
}

And how to use it

AA=12
read -p "Enter a value: " NEW_AA
# verify if consistent
[ $NEW_AA != $AA ] && Persist AA=$NEW_AA # no need to store it if it isn't modified

Done! :cool:
It modifies the script itself.
For regex and sed specialists : How could it be upgraded to use other types of variables?

2

That function definition syntax is neither fish nor fowl; it is a bash-only hybrid.

The POSIX syntax is:

Persist() { ...

The ksh syntax is:

function Persist { ...

That will only work with the GNU version of sed.

The 'which' command is not standard and some versions may produce unpredictable results; use 'type' instead.

There is no need for the 'basename' command in any POSIX shell.

In this script there is no need for either type or basename. $0 contains the path to the script.

sed ... "$0"

That is generally not good practice. It is better to use a configuration file.

sed -i "s/^$V=.[^ ]*/$1/" "$0" || return 1
3

Allright, i was angry if the script was called another way.

Yes, but just for one value ?

sed -i "s/^$V=.[^ ]*/$1/" "$0" || return 1

[/quote]
Thank You.
With your regex, the affectation statement should be alone on the line but it's not a problem.