Adding values concatenating values

Shell Programming and Scripting
1

I have the following script in a shell
# The start of a filename

 
file=$(ls -tr $EMT*.dat | tail -1) # Select the latest file echo $file
file_seq=$( < /u02/sct/banner/bandev2/xxxxxx/misc/EFTSQL.dat)
echo $file_seq
file2 = '$file_seq + 1' 
echo $file2

It is reading a file EFTSQL.dat (just one record 1234)

Here are the results:

 
+ ls -tr 3526_337092.dat EFT1234.dat HISTOGRAM200910.dat Histogram_200910.dat eluppdtop.dat idoc.dat lockbox_payments.dat
EFT1234.dat # Select the latest file echo 
file_seq=+ + 0< /u02/sct/banner/bandev2/middlebury/misc/EFTSQL.dat
0< /u02/sct/banner/bandev2/middlebury/misc/EFTSQL.dat
1234
echo 
file2 = ' + 1' 
echo

now I want to add 1 and stored in file2, so I ended with 1235
then I need to concatenated. EMTFile2.DAT
SO I ended with EMT12345.dat and stored in a variable so I can rename
a file that I just ftp with that name..
this part seems to be working

file_seq=$( < /u02/sct/banner/bandev2/xxxxxx/misc/EFTSQL.dat)
echo $file_seq

but this part is not

file2 = '$file_seq + 1'

and how I concatenate the values EMT||FILE2||.DAT
SO I ended with EMT12345.dat

2 
# file_seq=4
# file2=$(($file_seq+1))
# echo $file2
5
3

Ineed to end with 1235 no 5
1234 + 1 = 1235

4 
#  file_seq=1234
# file2=$(($file_seq+1))
# echo $file2
1235