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9.3 Field Widths with printf

Another useful feature of printf conversion (the % directives) lies in the area of field widths. These are values included in the % conversion directive to specify the width of a field and are especially useful in lining up columns of data. The field width value is placed between the % and the conversion character such as:

printf "%7d\n", 12345;
printf "%7d\n", 123;

will create right justified output:

12345
  123

Negative values can be used to create left justified fixed width data fields. This is of particular use when creating multi-column data output:

printf "%-10d", 12345;
printf "%-10d\n", 123;
printf "%-10d", 1;
printf "%-10d\n", 123456;

This will output the data in left justified columns:

12345     123
1         123456

The conversion value can also be used to control the number of decimal places displayed for floating point (%f) numbers:

printf "%15.3f\n", 53/9;
printf "%15.4f\n", 53/9;
printf "%15.7f\n", 53/9;

This will output right justified data with varying numbers of digits after the decimal point as defined in the conversions:

    5.889
   5.8889
5.8888889

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