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units(1): Refactor the manual page and update usage information

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Changes to units.1:

- Change the description to a more descriptive "conversion calculator".
- Sort options.
- Split the description into sections to make it easier to navigate the
  manual page.
- Improve the description of various options.
- Document the default value of the output format.
- Use more mdoc macros for better readability.
- Document the behavior of the PATH environmental variable.
- Improve examples.
- Add sections: EXIT STATUS, DIAGNOSTICS, and HISTORY.
- Document that units(1) cannot convert negative values and it handles long
  unit lists poorly.
- Update the documentation of the -V flag to match the implementation.
  units(1) prints its version and the units data file instead of its
  version and usage information.

Changes to units.c:

- Update usage information.
- Sort longopts elements.

This commit does not attempts to change the current behavior of units(1).
What's left to do is probably defining a better versioning (at the moment
units(1) always reports "FreeBSD units" as its version) and changing the
behavior of the -V flag to only print version.

Reviewed by:	allanjude (earlier version), bcr
Approved by:	bcr (mentor)
Differential Revision:	https://reviews.freebsd.org/D18977
This commit is contained in:
Mateusz Piotrowski 2020-02-03 15:22:46 +00:00
parent 59606417c4
commit 4a3b87e295
2 changed files with 379 additions and 123 deletions
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496
usr.bin/units/units.1
View File

@ -1,115 +1,126 @@
.\" $FreeBSD$
.Dd August 12, 2017
.Dd February 3, 2020
.Dt UNITS 1
.Os
.Sh NAME
.Nm units
.Nd conversion program
.Nd conversion calculator
.Sh SYNOPSIS
.Nm
.Op Fl f Ar filename
.Op Fl H Ar filename
.Op Fl qvUV
.Op Ar from-unit to-unit
.Sh OPTIONS
The following options are available:
.Bl -tag -width indent
.It Fl h \&No , Fl -help
Show an overview of options
.It Fl f Ar filename \&No , Fl -file Ar filename
Specify the name of the units data file to load.
.It Fl H Ar filename \&No , Fl -history Ar filename
Ignored, for compatibility with GNU units.
.It Fl e , Fl -exponential
Behave as if -o '%6e' was typed.
.It Fl q \&No , Fl -quiet
Suppress prompting of the user for units and the display of statistics
about the number of units loaded.
.It Fl U \&No , Fl -unitsfile
If the default unit file exists prints its location.
If not, print
.Qo
Units data file not found
.Qc
.It Fl t \&No , Fl -terse
Only print the result. This is used when calling
.Nm
from other programs for easy to parse results.
.It Fl v \&No , Fl -verbose
Print the units in the conversion output.
Be more verbose in general.
.It Fl o Ar format \&No , Fl -output-format Ar format
Select the output format string by which numbers are printed.
.It Fl V \&No , Fl -version
Print the version number, usage, and then exit.
.It Ar from-unit to-unit
Allow a single unit conversion to be done directly from the command
line.
The program will not print prompts.
It will print out the
result of the single specified conversion.
.El
.Op Fl ehqtUVv
.Op Fl f Ar unitsfile
.Op Fl o Ar format
.Op Ar from to
.Sh DESCRIPTION
The
.Nm
program converts quantities expressed in various scales to
their equivalents in other scales.
The
.Nm
program can only
It can only
handle multiplicative or affine scale changes.
It works interactively by prompting
the user for input:
.Bd -literal
You have: meters
You want: feet
* 3.2808399
/ 0.3048
You have: cm^3
You want: gallons
* 0.00026417205
/ 3785.4118
You have: meters/s
You want: furlongs/fortnight
* 6012.8848
/ 0.00016630952
You have: 1|2 inch
You want: cm
* 1.27
/ 0.78740157
You have: 85 degF
You want: degC
29.444444
.Ed
.Pp
Powers of units can be specified using the '^' character as shown in
the example, or by simple concatenation: 'cm3' is equivalent to 'cm^3'.
Multiplication of units can be specified by using spaces, a dash or
an asterisk.
Division of units is indicated by the slash ('/').
Note that multiplication has a higher precedence than division,
so 'm/s/s' is the same as 'm/s^2' or 'm/s s'.
.Nm
can work interactively by prompting
the user for input
.Pq see Sx EXAMPLES
or non-interactively, providing a conversion for given arguments
.Ar from
and
.Ar to .
.Pp
The following options are available:
.Bl -tag -width "from to"
.It Fl e , Fl -exponential
Same as
.Fl o
.Cm %6e
(see the description of the
.Fl o
flag).
.It Fl f Ar unitsfile , Fl -file Ar unitsfile
Specify the name of the units data file to load.
This option may be specified multiple times.
.It Fl H Ar historyfile , Fl -history Ar historyfile
Ignored, for compatibility with GNU units.
.It Fl h , Fl -help
Show an overview of options.
.It Fl o Ar format , Fl -output-format Ar format
Select the output format string by which numbers are printed.
Defaults to
.Dq Li %.8g .
.It Fl q , Fl -quiet
Suppress prompting of the user for units and the display of statistics
about the number of units loaded.
.It Fl t , Fl -terse
Only print the result.
This is used when calling
.Nm
from other programs for easy to parse results.
.It Fl U , Fl -unitsfile
Print the location of the default unit file if it exists.
Otherwise, print
.Dq Units data file not found .
.It Fl V , Fl -version
Print the version number
.Pq which is fixed at Dq Fx units ,
the path to the units data file and exit.
.It Fl v , Fl -verbose
Print the units in the conversion output.
Be more verbose in general.
.It Ar from to
Allow a single unit conversion to be done directly from the command
line.
The program will not print prompts.
It will print out the result of the single specified conversion.
Both arguments, i.e.,
.Ar from
and
.Ar to ,
can be just a unit
.Pq e.g., Dq Cm cm ,
a quantity
.Pq e.g., Dq Cm 42 ,
or a quantity with a unit
.Pq e.g., Dq Cm 42 cm
.El
.Ss Mathematical operators
.Bl -dash -compact
.It
Powers of units can be specified using the
.Dq Ic ^
character as shown in the example, or by simple concatenation:
.Dq Ic cm3
is
equivalent to
.Dq Ic cm^3 .
See the
.Sx BUGS
section
for details on the limitations of exponent values.
.It
Multiplication of units can be specified by using spaces
.Pq Dq " " ,
a dash
.Pq Dq -
or an asterisk
.Pq Dq * .
.It
Division of units is indicated by the slash
.Pq Dq Ic / .
.It
Division of numbers
must be indicated using the vertical bar ('|').
To convert half a
meter, you would write '1|2 meter'.
If you write '1/2 meter' then the
units program would interpret that as equivalent to '0.5/meter'.
If you enter incompatible unit types, the units program will
print a message indicating that the units are not conformable and
it will display the reduced form for each unit:
.Bd -literal
You have: ergs/hour
You want: fathoms kg^2 / day
conformability error
2.7777778e-11 kg m^2 / sec^3
2.1166667e-05 kg^2 m / sec
.Ed
must be indicated using the vertical bar
.Pq Dq Ic \&| Ns .
.El
.Pp
Note that multiplication has a higher precedence than division,
so
.Dq Ic m/s/s
is the same as
.Dq Ic m/s^2
or
.Dq Ic m/s s .
.Ss Units
The conversion information is read from a units data file.
The default
file includes definitions for most familiar units, abbreviations and
@ -128,48 +139,165 @@ Some constants of nature included are:
.It "au astronomical unit"
.El
.Pp
The unit 'pound' is a unit of mass.
The unit
.Dq Ic pound
is a unit of mass.
Compound names are run together
so 'pound force' is a unit of force.
The unit 'ounce' is also a unit
of mass.
The fluid ounce is 'floz'.
so
.Dq Ic pound force
is a unit of force.
The unit
.Dq Ic ounce
is also a unit of mass.
The fluid ounce is
.Dq Ic floz .
British units that differ from
their US counterparts are prefixed with 'br', and currency is prefixed
with its country name: 'belgiumfranc', 'britainpound'.
their US counterparts are prefixed with
.Dq br ,
and currency is prefixed with its country name:
.Dq Ic belgiumfranc ,
.Dq Ic britainpound .
When searching
for a unit, if the specified string does not appear exactly as a unit
name, then
.Nm
will try to remove a trailing 's' or a
trailing 'es' and check again for a match.
.Pp
will try to remove a trailing
.Dq s
or a trailing
.Dq es
and check again for a match.
.Ss Units file format
To find out what units are available read the standard units file.
If you want to add your own units you can supply your own file.
A unit is specified on a single line by
giving its name and an equivalence.
Be careful to define
new units in terms of old ones so that a reduction leads to the
primitive units which are marked with '!' characters.
primitive units which are marked with
.Dq \&!
characters.
The
.Nm
program will not detect infinite loops that could be caused
by careless unit definitions.
Comments in the unit definition file
begin with a '#' or '/' character at the beginning of a line.
begin with a
.Dq #
or
.Dq /
character at the beginning of a line.
.Pp
Prefixes are defined in the same way as standard units, but with
a trailing dash at the end of the prefix name.
a trailing dash
.Pq Dq -
at the end of the prefix name.
If a unit is not found
even after removing trailing 's' or 'es', then it will be checked
against the list of prefixes.
even after removing trailing
.Dq s
or
.Dq es ,
then it will be checked against the list of prefixes.
Prefixes will be removed until a legal
base unit is identified.
.Sh ENVIRONMENT
.Bl -tag -width PATH
.It Ev PATH
The colon-separated list of root directories at which
.Nm
tries to find
.Pa /usr/share/misc/definitions.units .
.Pp
For example if
.Ev PATH
is set to
.Dq Li /tmp:/:/usr/local ,
no
.Fl f
flags are provided, and
.Pa /usr/share/misc/definitions.units
is missing then
.Nm
tries to open the following files as the default units file:
.Pa /tmp/usr/share/misc/definitions.units ,
.Pa /usr/share/misc/definitions.units ,
and
.Pa /usr/local/usr/share/misc/definitions.units .
.El
.Sh FILES
.Bl -tag -width /usr/share/misc/definitions.units -compact
.It Pa /usr/share/misc/definitions.units
The standard units file.
.El
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
.Bl -tag -width 0n
.It Sy Example 1 : No Interactive usage
.Pp
Here is an example of an interactive session where the user is prompted for
units:
.Bd -literal -offset 2n
.Li You have : Ic meters
.Li You want : Ic feet
* 3.2808399
/ 0.3048
.Li You have : Ic cm^3
.Li You want : Ic gallons
* 0.00026417205
/ 3785.4118
.Li You have : Ic meters/s
.Li You want : Ic furlongs/fortnight
* 6012.8848
/ 0.00016630952
.Li You have : Ic 1|2 inch
.Li You want : Ic cm
* 1.27
/ 0.78740157
.Li You have : Ic 85 degF
.Li You want : Ic degC
29.444444
.Ed
.It Sy Example 2 : No Difference between Do Ic \&| Dc No and Do Ic / Dc No division
.Pp
The following command shows how to convert half a meter to centimeters.
.Bd -literal -offset 2n
.Li $ Ic units '1|2 meter' cm
* 50
/ 0.02
.Ed
.Pp
.Nm
prints the expected result because the division operator for numbers
.Pq Dq Li \&|
was used.
.Pp
Using the division operator for units
.Pq Dq Li /
would result in an error:
.Bd -literal -offset 2n
.Li $ Ic units '1/2 meter' cm
conformability error
0.5 / m
0.01 m
.Ed
.Pp
It is because
.Nm
interprets
.Dq Ic 1/2 meter
as
.Dq Ic 0.5/meter ,
which is not conformable to
.Dq Ic cm .
.It Sy Example 3 : No Simple units file
Here is an example of a short units file that defines some basic
units.
units:
.Pp
.Bl -column -offset indent -compact "minute"
.Bl -column -offset 2n -compact "minute"
.It "m !a!"
.It "sec !b!"
.It "micro- 1e-6"
@ -179,21 +307,122 @@ units.
.It "ft 12 inches"
.It "mile 5280 ft"
.El
.Sh FILES
.Bl -tag -width /usr/share/misc/definitions.units -compact
.It Pa /usr/share/misc/definitions.units
the standard units library
.It Sy Example 4 : No Viewing units and conversions of the default units file
The following shell one-liner allows the user to view the contents of the
default units file:
.Bd -literal -offset 2n
.Li $ Ic less \&"$(units -U)"
.Ed
.El
.Sh DIAGNOSTICS
.Bl -diag
.It can't find units file '%s'
The default units file is not in its default location
.Pq see Sx FILES
and it is not present in any file tree starting with their roots at directories from
.Ev PATH
.Pq see Sx ENVIRONMENT .
.It cap_rights_limit\&() failed
See
.Xr capsicum 4 .
.It conformability error
It is not possible to reduce the given units to one common unit:
they are not conformable.
Instead of a conversion,
.Nm
will display the reduced form for each provided unit:
.Bd -literal -offset 2n
.Li You have : Ic ergs/hour
.Li You want : Ic fathoms kg^2 / day
conformability error
2.7777778e-11 kg m^2 / sec^3
2.1166667e-05 kg^2 m / sec
.Ed
.It Could not initialize history
See
.Xr editline 3 .
.It dupstr
.Xr strdup 3
failed.
.It memory for prefixes exceeded in line %d
Over 100 prefixes were defined.
.It memory for units exceeded in line %d
Over 1000 prefixes were defined.
.It memory overflow in unit reduction
The requested conversion involves too many units
.Pq see Sx BUGS .
.It redefinition of prefix '%s' on line %d ignored
.No ""
.It redefinition of unit '%s' on line %d ignored
.No ""
.It unexpected end of prefix on line %d
.No ""
.It unexpected end of unit on line %d
.No ""
.It Units data file not found
The default units file is missing.
.It unable to enter capability mode
See
.Xr capsicum 4 .
.It unable to open units file '%s'
One of the user-specified units files cannot be opened.
.It unit reduces to zero
.No ""
.It unknown unit '%s'
The provided unit cannot be found in the units file.
.It WARNING: conversion of non-proportional quantities.
.Nm
may fail to convert
.Ar from
to
.Ar to
because the units are not proportional.
The warning is printed when a quantity is a part of the
.Ar to
argument.
It can be illustrated on an example of conversion from Fahrenheit to Celsius:
.Bd -literal -offset 2n
.Li $ Ic units \&"degF" \&"degC"
(-> x*0.55555556g -17.777778g)
(<- y*1.8g 32g)
.Li $ Ic units \&"degF" \&"1 degC"
WARNING: conversion of non-proportional quantities.
(-> x*0.55555556g -17.777778g)
(<- y*1.8g 32g)
.Li $ Ic units \&"1 degF" \&"1 degC"
WARNING: conversion of non-proportional quantities.
-17.222222
.Ed
.El
.Sh SEE ALSO
.Xr bc 1
.Sh HISTORY
The
.Nm
first appeared in
.Nx
and was ported to
.Fx 2.2.0 .
.Pp
The manual page was significantly rewritten in
.Fx 13.0
by
.An Mateusz Piotrowski Aq Mt 0mp@FreeBSD.org .
.Sh AUTHORS
.An Adrian Mariano Aq Mt adrian@cam.cornell.edu
.Sh BUGS
The effect of including a '/' in a prefix is surprising.
The effect of including a
.Dq /
in a prefix is surprising.
.Pp
Exponents entered by the user can be only one digit.
You can work around this by multiplying several terms.
.Pp
The user must use | to indicate division of numbers and / to
indicate division of symbols.
The user must use
.Dq Ic \&|
to indicate division of numbers and
.Dq Ic /
to indicate division of symbols.
This distinction should not
be necessary.
.Pp
@ -203,3 +432,30 @@ of the units converted and on the length of the data file.
The program should use a hash table to store units so that
it does not take so long to load the units list and check
for duplication.
.Pp
It is not possible to convert a negative value.
.Pp
The
.Nm
program
does not handle reductions of long lists of units very well:
.Bd -literal -offset 2n
.Li $ Ic units \&"$(yes m | head -n 154)" \&"$(yes cm | head -n 154)"
* 1e+308
/ 1e-308
.Li $ Ic units \&"$(yes m | head -n 333)" \&"$(yes cm | head -n 333)"
* inf
/ 0
.Li $ Ic units \&"$(yes m | head -n 500)" \&"$(yes cm | head -n 500)"
units: memory overflow in unit reduction
conformability error
1 m^500
1 centi cm^499
.Li $ Ic units \&"$(yes m | head -n 501)" \&"$(yes cm | head -n 501)"
units: memory overflow in unit reduction
units: memory overflow in unit reduction
units: memory overflow in unit reduction
conformability error
1 m^500
1 centi cm^499
.Ed

6
usr.bin/units/units.c
View File

@ -731,21 +731,21 @@ static void __dead2
usage(void)
{
fprintf(stderr,
"usage: units [-f unitsfile] [-H historyfile] [-UVq] [from-unit to-unit]\n");
"usage: units [-ehqtUVv] [-f unitsfile] [-o format] [from to]\n");
exit(3);
}
static struct option longopts[] = {
{"help", no_argument, NULL, 'h'},
{"exponential", no_argument, NULL, 'e'},
{"file", required_argument, NULL, 'f'},
{"history", required_argument, NULL, 'H'},
{"help", no_argument, NULL, 'h'},
{"output-format", required_argument, NULL, 'o'},
{"quiet", no_argument, NULL, 'q'},
{"terse", no_argument, NULL, 't'},
{"unitsfile", no_argument, NULL, 'U'},
{"verbose", no_argument, NULL, 'v'},
{"version", no_argument, NULL, 'V'},
{"verbose", no_argument, NULL, 'v'},
{ 0, 0, 0, 0 }
};