infos = Information about the mathcheck plugin is in keys below
infos/author = Thomas Waser thoma.nosp@m.s.wa.nosp@m.ser@l.nosp@m.ibel.nosp@m.ektra.nosp@m..org
infos/licence = BSD
infos/provides = check
infos/needs =
infos/placements = presetstorage
infos/status = maintained unittest shelltest nodep discouraged
infos/metadata = check/math
infos/description = validates a set of keys through a mathematical expression

Introduction

Compares a key value to a mathematical expression using polish prefix notation defined in the check/math metakey. Operations are + - / * . Operants are keys with names relative to the parent key. How the values are compared is specified at the beginning of the metakey using the conditions <, <=, ==, !=, =>, >, := := is used to set key values. All values are interpreted as double floating point values.

Installation

See installation. The package is called libelektra5-extra.

Keynames

Keynames are all either relative to to-be-tested key (starting with ./ or ../), relative to the parentkey (starting with @/) or absolute (e.g. system:/key).

Examples

check/math = "== + ../testval1 + ../testval2 ../testval3" compares the keyvalue to the sum of testval1-3 and yields an error if the values are not equal. check/math = "<= - @/testval1 * @/testval2 @/testval3" tests if the keyvalue is less than or equal to testval1 - (testval2 * testval3) and yields an error if not.

Full example:

# Backup-and-Restore:user:/tests/mathcheck
 
sudo kdb mount mathcheck.dump user:/tests/mathcheck mathcheck
 
kdb set user:/tests/mathcheck/a 3.1
kdb set user:/tests/mathcheck/b 4.5
kdb set user:/tests/mathcheck/k 7.6
kdb meta-set user:/tests/mathcheck/k check/math "== + ../a ../b"
 
# should fail
kdb set user:/tests/mathcheck/k 7.7
# RET:5
# ERROR:C03200
# Set string to "7.7"
# Sorry, module mathcheck issued the error C03200:
# invalid value: 7.7 != 7.6

To calculate values on-demand you can use:

kdb meta-set user:/tests/mathcheck/k check/math ":= + @/a @/b"
kdb set user:/tests/mathcheck/a 8.0
kdb set user:/tests/mathcheck/b 4.5
 
kdb get user:/tests/mathcheck/k
#> 12.5
 
kdb set user:/tests/mathcheck/a 5.5
 
kdb get user:/tests/mathcheck/k
#> 10

It also works with constants:

kdb meta-set user:/tests/mathcheck/k check/math ":= + ../a '5'"
kdb set user:/tests/mathcheck/a 5.5
 
kdb get user:/tests/mathcheck/k
#> 10.5
 
kdb set user:/tests/mathcheck/a 8.0
 
kdb get user:/tests/mathcheck/k
#> 13
 
#cleanup
kdb rm -r user:/tests/mathcheck
sudo kdb umount user:/tests/mathcheck