Linux – Sorts files in a directory based on a numeric index in the file name

I used a for loop in my script, like this….

 for var in ipsec_packet*.txt; do
 echo $var
 done

Output

ipsec_packet10.txt
ipsec_packet11.txt
ipsec_packet12.txt
ipsec_packet13.txt
ipsec_packet14.txt
ipsec_packet15.txt
ipsec_packet16.txt
ipsec_packet17.txt
ipsec_packet18.txt
ipsec_packet1.txt
ipsec_packet2.txt
ipsec_packet3.txt
ipsec_packet4.txt
ipsec_packet5.txt
ipsec_packet6.txt
ipsec_packet7.txt
ipsec_packet8.txt
ipsec_packet9.txt

But I want them to start at 1 in this sort order to the largest available value (here 18)…

ipsec_packet1.txt
ipsec_packet2.txt
... 
...
ipsec_packet18.txt

I tried sort -n k14 but it didn’t help. Please suggest me some sort variants that can help me or any other bash/awk feature.

You can try using sort with the -V option for natural sorting of numbers in text:

for var in `ls ipsec_packet*.txt | sort -V`; do  echo $var; done