Create conditional bash script code - regex

Question

I use the following code to load some text file with emails
and create users in the system with user password.
the text file contain emails like following
abc#gmail.com
BDD#gmail.com
ZZZ#gmail.com
In case the name is coming with upper case I convert it to lower case, I was able to make it work.
Now I need to support another input instead of email
e.g.
P123456
Z877777
but now I dont want for this type of input to convert it to lower case
someting like
if(emailpattern )
convert to lower
else
Not
This is the code which works but I failed to make it work...
for user in $(cat ${users} | awk -F";" '{ print $1 }'); do
user=$(echo ${user} | tr "[:upper:]" "[:lower:]")
log "cf create-user ${user} ${passwd}"
#Here we are creating email user in the sys
cf create-user ${user} ${passwd} 2>&1 |
tee -a ${dir}/${scriptname}.log ||
{ log "ERROR cf create-user ${user} failed" ;
errorcount=$[errorcount + 1]; }
done

Answer 1

You can use:
while IFS= read -r user; do
# convert to lowercase only when $user has # character
[[ $user == *#* ]] && user=$(tr "[:upper:]" "[:lower:]" <<< "$user")
log "cf create-user ${user} ${passwd}"
cf create-user ${user} ${passwd} 2>&1 |
tee -a ${dir}/${scriptname}.log ||
{ log "ERROR cf create-user ${user} failed" ;
errorcount=$[errorcount + 1]; }
done < <(awk -F ';' '{ print $1 }' "$users")

Answer 2

Assumptions:
input file consists of email addresses or names, each on a separate line
email addresses are to be converted to lower case
names are to be left as is (ie, no conversion to lower case)
all of the log/cf/tee/errorcount code functions as desired
Sample input file:
$ cat userlist
abc#gmail.com
BDD#gmail.com
ZZZ#gmail.com
P123456
Z877777
We'll start by using awk to conditionally convert email addresses to lower case:
$ awk '/#/ {$1=tolower($1)} 1' userlist
abc#gmail.com
bdd#gmail.com
zzz#gmail.com
P123456
Z877777
first we'll run the input file (userlist) through awk ...
/#/ : for lines that include an email address (ie, contains #) ...
$1=tolower($1) : convert the email address (field #1) to all lowercase, then ...
1 : true for all records and implies print all inputs to output
Now pipe the awk output to a while loop to perform the rest of the operations:
awk '/#/ {$1=tolower($1} 1}' userlist | while read user
do
log "cf create-user ${user} ${passwd}"
#Here we are creating email user in the sys
cf create-user ${user} ${passwd} 2>&1 |
tee -a ${dir}/${scriptname}.log ||
{ log "ERROR cf create-user ${user} failed" ;
errorcount=$((errorcount + 1)) ;
}
done
updated to correctly increment errorcount by 1

Answer 3

bash can lower-case text:
while IFS= read -r line; do
[[ $line == *#* ]] && line=${line,,}
# do stuff with "$line"
done