Shell Programming and Scripting

You haven't answered the questions I asked, so let's start from the beginning.

(I have reformatted your post so that it is easier to understand.)

Are there only four fields?
If there are more, what conditions must they meet?
If a field has a length greater the 0, then it is not null; or do you mean something else by "not null"?

This script checks the first four fields per line.

It also gives the line number where the error occurred.

Code:

errline=$( awk 'BEGIN { IFS = "\t" }
   NR <= 2 { next } ## skip the first two lines
   !/\t/ { exit 101 }  ## line does not contain a tab

   ## Fields 1 and 3 must be 9 characters and contain only digits
   length($1) != 9 || $1 ~ /[^0-9]/ { exit 110 }
   length($3) != 9 || $1 ~ /[^0-9]/ { exit 130 }

   ## Fields 2 and 4 must be 8 and 13 characters respectively
   length($2) != 8                  { exit 120 }
   length($4) != 13                 { exit 140 }

END { print NR }
' "$FILE"
)

var1=$?  ## Set variable to the exit code of the awk script

## Assign var2 based on awk's return code
case $var1 in
   101) var2="Not in tab-delimited format" ;;
   110) var2="Mismatch/Wrong Field one" ;;
   120) var2="Mismatch/Wrong Field two" ;;
   130) var2="Mismatch/Wrong Field three" ;;
   140) var2="Mismatch/Wrong Field four" ;;
esac

printf "Error number: %d, line %d\n" "$var1" "$errline"
printf "Error message: %s\n" "$var2"

Marvellous !!
Its working perfectly.

Thank you so much. I appreciate it.

It is not checking for tab-delimited format. The following is the error I am getting, can you pl help?

Script:
#!/bin/ksh

awk -F\t 'NR>=3 { ## to start from 3rd line
!/\t/ {exit 101} ## not working
if ( $2 ~ /^ *$/ || $2 ~ /[^0-9]/ || length($1)!=7 ) {exit 102}
if ( $6 ~ /^ *$/ || $6 ~ /[^0-9]/ || length($6) !=5 ) {exit 106}
}' $1
var1=$? ## set variable to the exit code of awk script

## Assign var2 based on awk's return code
case $var1 in
101) var2="File not in tab-delimited format" ;;
102) var2="Mismatch/Wrong Field2" ;;
106) var2="Mismatch/Wrong Field6" ;;
*) var2="Success" ;;
esac
print "$var1"
print "$var2"


I am getting error :
$ test7 sample.txt
awk: syntax error near line 2
awk: illegal statement near line 2
awk: bailing out near line 3

The sampe file is:
xxyyzz20070503100717001
abcd.txt000000027600000002
1234567 3809363 175268 849036 94425 284437
2271208 3809365 175268 849036 94425 284437