File: gawk.info,  Node: Labels Program,  Next: Word Sorting,  Prev: Translate Program,  Up: Miscellaneous Programs

11.3.4 Printing Mailing Labels
------------------------------

Here is a "real-world"(1) program.  This script reads lists of names and
addresses and generates mailing labels.  Each page of labels has 20
labels on it, two across and 10 down.  The addresses are guaranteed to
be no more than five lines of data.  Each address is separated from the
next by a blank line.

   The basic idea is to read 20 labels' worth of data.  Each line of
each label is stored in the 'line' array.  The single rule takes care of
filling the 'line' array and printing the page when 20 labels have been
read.

   The 'BEGIN' rule simply sets 'RS' to the empty string, so that 'awk'
splits records at blank lines (*note Records::).  It sets 'MAXLINES' to
100, because 100 is the maximum number of lines on the page (20 * 5 =
100).

   Most of the work is done in the 'printpage()' function.  The label
lines are stored sequentially in the 'line' array.  But they have to
print horizontally: 'line[1]' next to 'line[6]', 'line[2]' next to
'line[7]', and so on.  Two loops accomplish this.  The outer loop,
controlled by 'i', steps through every 10 lines of data; this is each
row of labels.  The inner loop, controlled by 'j', goes through the
lines within the row.  As 'j' goes from 0 to 4, 'i+j' is the 'j'th line
in the row, and 'i+j+5' is the entry next to it.  The output ends up
looking something like this:

     line 1          line 6
     line 2          line 7
     line 3          line 8
     line 4          line 9
     line 5          line 10
     ...

The 'printf' format string '%-41s' left-aligns the data and prints it
within a fixed-width field.

   As a final note, an extra blank line is printed at lines 21 and 61,
to keep the output lined up on the labels.  This is dependent on the
particular brand of labels in use when the program was written.  You
will also note that there are two blank lines at the top and two blank
lines at the bottom.

   The 'END' rule arranges to flush the final page of labels; there may
not have been an even multiple of 20 labels in the data:

     # labels.awk --- print mailing labels

     # Each label is 5 lines of data that may have blank lines.
     # The label sheets have 2 blank lines at the top and 2 at
     # the bottom.

     BEGIN    { RS = "" ; MAXLINES = 100 }

     function printpage(    i, j)
     {
         if (Nlines <= 0)
             return

         printf "\n\n"        # header

         for (i = 1; i <= Nlines; i += 10) {
             if (i == 21 || i == 61)
                 print ""
             for (j = 0; j < 5; j++) {
                 if (i + j > MAXLINES)
                     break
                 printf "   %-41s %s\n", line[i+j], line[i+j+5]
             }
             print ""
         }

         printf "\n\n"        # footer

         delete line
     }

     # main rule
     {
         if (Count >= 20) {
             printpage()
             Count = 0
             Nlines = 0
         }
         n = split($0, a, "\n")
         for (i = 1; i <= n; i++)
             line[++Nlines] = a[i]
         for (; i <= 5; i++)
             line[++Nlines] = ""
         Count++
     }

     END {
         printpage()
     }

   ---------- Footnotes ----------

   (1) "Real world" is defined as "a program actually used to get
something done."