File: gawk.info,  Node: Printf Examples,  Prev: Format Modifiers,  Up: Printf

5.5.4 Examples Using 'printf'
-----------------------------

The following simple example shows how to use 'printf' to make an
aligned table:

     awk '{ printf "%-10s %s\n", $1, $2 }' mail-list

This command prints the names of the people ('$1') in the file
'mail-list' as a string of 10 characters that are left-justified.  It
also prints the phone numbers ('$2') next on the line.  This produces an
aligned two-column table of names and phone numbers, as shown here:

     $ awk '{ printf "%-10s %s\n", $1, $2 }' mail-list
     -| Amelia     555-5553
     -| Anthony    555-3412
     -| Becky      555-7685
     -| Bill       555-1675
     -| Broderick  555-0542
     -| Camilla    555-2912
     -| Fabius     555-1234
     -| Julie      555-6699
     -| Martin     555-6480
     -| Samuel     555-3430
     -| Jean-Paul  555-2127

   In this case, the phone numbers had to be printed as strings because
the numbers are separated by dashes.  Printing the phone numbers as
numbers would have produced just the first three digits: '555'.  This
would have been pretty confusing.

   It wasn't necessary to specify a width for the phone numbers because
they are last on their lines.  They don't need to have spaces after
them.

   The table could be made to look even nicer by adding headings to the
tops of the columns.  This is done using a 'BEGIN' rule (*note
BEGIN/END::) so that the headers are only printed once, at the beginning
of the 'awk' program:

     awk 'BEGIN { print "Name      Number"
                  print "----      ------" }
                { printf "%-10s %s\n", $1, $2 }' mail-list

   The preceding example mixes 'print' and 'printf' statements in the
same program.  Using just 'printf' statements can produce the same
results:

     awk 'BEGIN { printf "%-10s %s\n", "Name", "Number"
                  printf "%-10s %s\n", "----", "------" }
                { printf "%-10s %s\n", $1, $2 }' mail-list

Printing each column heading with the same format specification used for
the column elements ensures that the headings are aligned just like the
columns.

   The fact that the same format specification is used three times can
be emphasized by storing it in a variable, like this:

     awk 'BEGIN { format = "%-10s %s\n"
                  printf format, "Name", "Number"
                  printf format, "----", "------" }
                { printf format, $1, $2 }' mail-list