Shell Programming and Scripting

******************************
Class 1A
Students absent are :
1. ABC
2. CDE
3. CPE

******************************
Class 2A
Students absent are :

******************************
Class 3A
Students absent are :

******************************
Class 17ACF
Students absent are :
1. ABCD
2. XYZ

******************************
Class 1A
Students absent are :
1. ABC
2. CDE
3. CPE

******************************
Class 17ACF
Students absent are :
1. ABCD
2. XYZ

man grep

scount=0
while read k
do

    if [ line starts with Class ]
    then
        put the line into a file1.txt
    
    elif [ line starts with Students ]
    then
        append the line into file1.txt
    
    elif [ line starts with a number ]
        scount+=1
        append the line into file1.txt
    elif [line is empty and scount >=1 ]
    then
        insert an empty line into file1.txt
        insert ****** into file1.txt
        append file1.txt data to file2.txt
        empty file1.txt
        scount=0
    elif [ line is empty and scount=0 ]
    then
        empty the file1.txt
    fi
done <"Sourcefile.txt"

awk     '/\*\*\*/               {if (CNT>4) for (i=1;i<=CNT;i++) print T[i]; CNT=0}
                                {T[++CNT]=$0}
         END                    {if (CNT>4) for (i=1;i<=CNT;i++) print T[i]}
        '  file
******************************
Class 1A
Students absent are :
1. ABC
2. CDE
3. CPE

******************************
Class 17ACF
Students absent are :
1. ABCD
2. XYZ

awk'(A=gsub (/\n/, "&"))>4||A==0' RS="*" ORS="*" file
******************************
Class 1A
Students absent are :
1. ABC
2. CDE
3. CPE

****************************************************************************************
Class 17ACF
Students absent are :
1. ABCD
2. XYZ
*

awk     '/\*\*\*/               {if (CNT>4) for (i=1;i<=CNT;i++) print T[i]; CNT=0}
                                {T[++CNT]=$0}
         END                    {if (CNT>4) for (i=1;i<=CNT;i++) print T[i]}
        '  file

awk '
$1~/\*\*\*/ {if (c>0) print buf; c=0; buf=$0; next}
{buf=buf RS $0}
$1~/[0-9]+\./ {c++}
END {if (c>0) print buf}
' file