(gawk.info)Printf Examples

Examples Using `printf'
-----------------------

   Here is how to use `printf' to make an aligned table:

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

prints the names of bulletin boards (`$1') of the file `BBS-list' as a
string of 10 characters, left justified.  It also prints the phone
numbers (`$2') afterward on the line.  This produces an aligned
two-column table of names and phone numbers:

     $ awk '{ printf "%-10s %s\n", $1, $2 }' BBS-list
     -| aardvark   555-5553
     -| alpo-net   555-3412
     -| barfly     555-7685
     -| bites      555-1675
     -| camelot    555-0542
     -| core       555-2912
     -| fooey      555-1234
     -| foot       555-6699
     -| macfoo     555-6480
     -| sdace      555-3430
     -| sabafoo    555-2127

   Did you notice that we did not specify that the phone numbers be
printed as numbers?  They had to be printed as strings because the
numbers are separated by a dash.  If we had tried to print the phone
numbers as numbers, all we would have gotten would have been the first
three digits, `555'.  This would have been pretty confusing.

   We did not specify a width for the phone numbers because they are the
last things on their lines.  We don't need to put spaces after them.

   We could make our table look even nicer by adding headings to the
tops of the columns.  To do this, we use the `BEGIN' pattern (Note: The
`BEGIN' and `END' Special Patterns.) to force the header to
be printed only once, at the beginning of the `awk' program:

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

   Did you notice that we mixed `print' and `printf' statements in the
above example?  We could have used just `printf' statements to get the
same results:

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

By printing each column heading with the same format specification used
for the elements of the column, we have made sure 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 }' BBS-list

   See if you can use the `printf' statement to line up the headings and
table data for our `inventory-shipped' example covered earlier in the
section on the `print' statement (Note: The `print' Statement.).