Setting Options Interactively (Units: A Unit Conversion Program and Scientific Calculator)

11 Setting Options Interactively

Many command-line options can also be set interactively, obviating the need to quit and restart units to change the values. This can be especially helpful for Windows users who start units from a shortcut.

Typing set will display a list of all options that can be set interactively, as well as the current and possible values; options set to other than default values have an asterisk (‘*’) prepended. For example,

You have: set
  q[uiet] = no         (y|n) do/don't suppress prompting
  o[neline] = no       (y|n) do/don't suppress the second line of output
  st[rict] = no        (y|n) do/don't suppress reciprocal unit conversion
                             (e.g. Hz<->s)
  t[erse] = no         (y|n) do/don't give very terse output
  c[ompact] = no       (y|n) do/don't suppress printing tab, SETFLAG, and '/'
                             characters in results
  v[erbose] = 1        (0|1|2) amount of information shown
 *d[igits] = 9         number of significant digits in output
  e[ponential] = no    (y|n) do/don't use exponential ("scientific") notation
 *f[ormat] = %.9g      printf(3) format specification
  u[nitlists] = yes    (y|n) do/don't allow conversion to unit lists
  r[ound] = no         (y|n) do/don't round last element of unit list output
                             to an integer
  sh[owfactor] = no    (y|n) do/don't show non-unity factor before 1|x
                             in multi-unit output

Characters within the square brackets are optional, so settings can be changed by entering only one or two characters.

The syntax for setting options is set option = value; the spaces around the ‘=’ sign are optional.

Some settings are Boolean, enabled by entering yes (or just y) and disabled by entering no (or just n). For example,

You have: set quiet = y
  quiet = yes

Other settings take an integer value; for example,

You have: set d=11
  digits = 11
  format = %.11g

The format setting takes a string, the format specification for the printf function in the C programming language; for example,

You have: set format = %.9g
  format = %.9g

Typing set option will display the current value of option, for example

You have: set u
  unitlists = yes
You have: set d
  digits = 8
  format = %.8g

For the digits and exponential options, the value of format is also shown.