Shell Programming and Scripting

pattern1 = AB???
pattern2 = abc??*

if  file_name == <patten1>
then
       ...
elif  file_name == <pattern2>
     ---
fi

DIR=/your/directory/to/search
pattern1="AB???"
ls $DIR/$pattern1 2>/dev/null || echo "No file found matching the pattern"

DIR=/your/directory/to/search
pattern1="AB???"
ls $DIR/$pattern1 1>/dev/null 2>/dev/null
if [ $? -eq 0 ]
then
  echo "Match found"
else
  echo "No match found"
fi

file_name="AB1000.csv"
case file_name in
   AB???*)  Do the first AB action
          Do the second AB action ;;
   abc??*)  Do the first abc action
          Do the second abc action ;;
   *)    Do actions for no match ;;
esac

file_name="AB1000.csv"

test_file_name="${file_name#AB}"

if [ "$test_file_name" != "$file_name" ]
then
   echo "Matched AB"
fi


test_file_name="${file_name#abc}"

if [ "$test_file_name" != "$file_name" ]
then
   echo "Matched abc"
fi