Shell Programming and Scripting

123456,22222,John,0,xyz
234567,22222,John1,1,cde
43212,3333,Jean,3,pip
84324,3333,Abel,2,cat

123456,22222,John,0,xyz;234567,22222,John1,1,cde
43212,3333,Jean,3,pip;84324,3333,Abel,2,cat

awk -F, '{ A[$2]=A[$2]";"$0 } END { for(X in A) print substr(A[X],2) }' <<EOF
123456,22222,John,0,xyz
234567,22222,John1,1,cde
43212,3333,Jean,3,pip
84324,3333,Abel,2,cat
EOF
43212,3333,Jean,3,pip;84324,3333,Abel,2,cat
123456,22222,John,0,xyz;234567,22222,John1,1,cde

$

# -F, means "split columns on comma", so it knows that 22222 is column 2, or $2.
# $ means column in awk and has absolutely nothing to do with shell variables.
#
# The single quote begins a single block of text which the shell feeds into awk unchanged:
awk -F, '
# A[2222]=A[2222] + ";" + entire current line
# Note that whenever A[2222] is empty, this leaves ; in front.
# It gets removed later with substr.
{ A[$2]=A[$2]";"$0 }

END { # Run this when the file runs out of lines
        for(X in A)        # For each index X in array A
         print substr(A[X],2)        # Print characters 2-n of A[X]
}' input-filename > output-filename

awk '{printf "%s;", $0; getline; print}' file
123456,22222,John,0,xyz;234567,22222,John1,1,cde
43212,3333,Jean,3,pip;84324,3333,Abel,2,cat

awk 'ORS=(FNR%2)?FS:RS' FS=';' myFile