Log from start of script, but decide on log filename during the script

Question

I do not know how to write that part of bash script which enables me to write to the file which is created in the middle of the script (because it depends on user input) but I want to write output from the beginning.

Example:

#!/bin/bash
<start_of_logging>
<code>
 read -p "Enter your city: " city
 touch ${city}
<code>
<end_of_logging>

Script does not know what user put in city so if I am correct I am not able to logging from <start_of_logging> part or is there any workaround? I mean I want to log everything from the beginning and write it out to the file which is called like a city provided by an user.

Answer 1

So to summarize the comments, the code could be something like this:

#!/bin/bash
### start logging using temporary logfile
logfile="$(mktemp)" # possibly add options to mktemp, like "-p dir" as needed

# add a message to logfile
log()
{
    echo "$@" >> "$logfile"
}
### code
 read -p "Enter your city: " city
 touch ${city}
### update logfile
newlogfile="something_with_${city}.log"
log "renaming temporary logfile $logfile to $newlogfile"
mv "$logfile" "$newlogfile" && logfile="$newlogfile"
log "now logging to $logfile"
###

When running the script with input "testtown", I got:

Enter your city: testtown
me@pc:~> cat something_with_testtown.log
renaming temporary logfile /tmp/tmp.alKCBTV7ti to something_with_testtown.log
now logging to something_with_testtown.log

Important note

Hopefully nobody enters :; rm -rf / (or similar) as city...