create unique new day-stamped file from a given file stem and extension

create-unique-new-daystamped-file-snippet.sh

#!/bin/bash

# bash snippet:
# create unique new day-stamped file from a given file stem and extension
#
# note the for-loop fto find the first unique (=non-existent) file with 
# a given name
#

fnstem="a-file" # here goes the file stem before unifiying
fnext="txt" # here goes the file extenmstion before unifiying

fnstem="${fnstem}_`date +%Y%m%d`"
foundpostfix=false
for postfix in "" "_1" "_2" "_3" "_4" "_5" "_6" "_7" "_8" "_9"; do 
    fn="${fnstem}$postfix.$fnext"
    if [ ! -f "$fn" ]; then
        foundpostfix=true
        break
    fi
done

if [ ! "$foundpostfix" = true ]; then
    echo "error: could not generate a free filename (last try \"$fn\")" >&2
    exit 98
fi

echo "$fn" # use the unique name