Performance impace of spawning shell processes from Dovecot [was: quota_over_flag examples?]

[E.B.]

> > I can't find any posts on this list for peoples using quota_over_flag
> >
> > http://wiki2.dovecot.org/Quota/Configuration#Overquota-flag_.28v2.2.16.2B-.29
> >
> > If my userdb is sql what would be best script to use in terms of performance?
> > (I mean if over-quota-flag triggers script every time it changes and the script
> > calls CLI mysql client isn't all this so expensive to spawn a new shell session
> > which spawns a mysql client?)
>
> I have a post-login script updating a "lastlogin" timestamp every time a
> user logs in. This can happen many times per second in busy hours. The
> only noticeable load is on the mysql _server_ (namely, some I/O). The
> shell + mysql client load is not noticeable at all.

Thank you. Is this common for most people === repeatedly spawning shell
scripts from Dovecot processes is not impact performance? I thought it's
why apps are written as daemons especially for many times a second as
you say!

> Don't use bash, of course!

Hmm well I didn't not know about this. On CentOS--

lrwxrwxrwx. 1 root root 4 Apr  5 10:31 /bin/sh -> bash*

Can you state the reasons you say do not use bash so I can google about
them?