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md_src_plugins_mathcheck_README(3elektra) Elektra md_src_plugins_mathcheck_README(3elektra)

NAME

md_src_plugins_mathcheck_README - Plugin: mathcheck

  • infos = Information about the mathcheck plugin is in keys below
  • infos/author = Thomas Waser thomas.waser@libelektra.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

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.

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:/examples/mathcheck
sudo kdb mount mathcheck.dump /examples/mathcheck dump mathcheck
kdb set /examples/mathcheck/a 3.1
kdb set /examples/mathcheck/b 4.5
kdb set /examples/mathcheck/k 7.6
kdb setmeta user/examples/mathcheck/k check/math "== + ../a ../b"
# should fail
kdb set /examples/mathcheck/k 7.7
# RET:5
# ERRORS:123
# Set string to "7.7"
# The command set failed while accessing the key database with the info:
# Error (#123) occurred!
# Description: invalid value
# Ingroup: plugin
# Module: mathcheck
# At: /home/thomas/Dev/Elektra/libelektra/src/plugins/mathcheck/mathcheck.c:399
# Reason: 7.7 != 7.6
# Mountpoint: /examples/mathcheck
# Configfile: /home/thomas/.config/mathcheck.dump.25680:1478749409.938013.tmp


To calculate values on-demand you can use:

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


It also works with constants:

kdb setmeta user/examples/mathcheck/k check/math ":= + ../a '5'"
kdb set /examples/mathcheck/a 5.5
kdb get /examples/mathcheck/k
#> 10.5
kdb set /examples/mathcheck/a 8.0
kdb get /examples/mathcheck/k
#> 13
#cleanup
kdb rm -r /examples/mathcheck
sudo kdb umount /examples/mathcheck
Mon Jan 15 2018 Version 0.8.20