I am writing a ksh which has to load 7 files(.dat files) from input directory into oracle tables using sql loader. The process has to take each file at a time and once if it is loaded succesfully using sql loader into oracle tables then the process has to pick next file and load it into oracle tables. Here we do not know when we will have the files in the input directory. So my script has to check for a file, if exists then load it if it does not exists then has to wait for a period of 15 mins and then start looking for a file and so on. Below is the code which i have written. Any help is greatly appreciated.

 
while [ 1 ]
do

## check for .dat files in inputdir
FILE_EXISTS="0"
FILE_EXISTS=`ls ${INPUT_DIR}/*.txt | wc -l`
echo "value in File_exist is $FILE_EXISTS"
if [ $FILE_EXISTS -eq 0 ]; then
   continue;
fi

##  if files exists then start processing them
for file in `ls ${INPUT_DIR}/*.txt`
do
   execute_sql_loader $file
   RC=?
   echo "sqlldr generated output $RC"
      if [ $RC -ne 0 ]; then
         continue;
      fi
done

sleep 10;
done

please indent your code so its easier to read.

This is the way I'd approach it:

#/usr/bin/env ksh

if ! cd $INPUT_DIR
then
        echo "unable to switch to $INPUT_DIR"
        exit 1
fi

need=7                 # number of files needed before we are finished
while (( $need > 0 ))
do
        for file in *.dat          # for all .dat files currently in the directory 
        do
                echo "processing: $file"
                execute_sql_loader $file
                rc=$?
                if (( $rc > 0 ))
                then
                        echo "error loading file: $file rc=$rc"
                else
                        echo "file loaded successfully: $file"
                fi


                mv $file $file.processed        # prevent finding it again; maybe delete it instead?
                need=$(( $need - 1 ))         # one less file needed
        done

        if (( need > 0 ))
        then
                echo "$(date) waiting 15m before making next pass; need $need files"
                sleep $(( 15 * 60 ))                    # wait 15 minutes before trying again
        fi
done