Shell Programming and Scripting

2014-10-21:Rand1
2014-11-02:Rand2
2014-11-02:Rand3
2014-11-02:Rand4
2014-11-03:Rand5
2014-11-04:Rand6
2014-11-04:Rand7

2014-10-21:Rand1
2014-11-02:Rand2:Rand3:Rand4
2014-11-03:Rand5
2014-11-04:Rand6:Rand7

awk -F: '
        {
                A[$1] = A[$1] ? A[$1] FS $2 : $2
        }
        END {
                for ( k in A )
                        print k FS A[k]
        }
' file | sort -t: -k1

awk -F: '$1!=p{if(p)print s; s=$0; p=$1; next}{s=s FS $2} END{print s}' file

 
awk -F: '
  END{for(x in O)print x FS O[x]}{O[$1]=O[$1]?O[$1]OFS$2:$2}
  ' OFS=: file | sort -t: -k1,1