Shell Programming and Scripting

Col_1
SW_MH2_ST
ST_F72_9S
SW_MH3_S6
Col_2
SW_MH3_AS7
ST_S15_9CH
SW_MH3_AS8
SW_MH3_ST
Col_3
ST_M93_SZ
ST_C16_TC

Col_1
ST_F72_9S
SW_MH2_ST
SW_MH3_S6
Col_2
ST_S15_9CH
SW_MH3_AS7
SW_MH3_AS8
SW_MH3_ST
Col_3
ST_C16_TC
ST_M93_SZ

awk '
/^Col/ {col[++c]=$0; next;}
{data[c,NR]=$0;}
END {
   for (i=1; i<=c ; i++) {
      print col[i];
      for (j=1; j<=NR; j++) if (data[i,j]) ar[data[i,j]]=data[i,j];
      n=asort(ar);
      for (l=1; l<=n; l++) print ar[l];
      delete ar;
   }
} ' Input.txt

awk '
/^Col/ {col[++c]=$0; next;}
{data[c,NR]=$0;}
END {
   for (i=1; i<=c ; i++) {
      print col[i];
      for (j=1; j<=NR; j++) if (data[i,j]) ar=ar "\n" data[i,j];
      sub("^\n","", ar);
      sort="sort";
      print ar | sort;
      close(sort);
      ar="";
   }
} ' Input.txt