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| [[Anchor(faq22)]] == How can I calculate with floating point numbers instead of just integers? == ["BASH"] does not have built-in floating point arithmetic: {{{ $ echo $((10/3)) 3 }}} For better precision, an external program must be used, e.g. {{{bc}}}, {{{awk}}} or {{{dc}}}: {{{ $ echo "scale=3; 10/3" | bc 3.333 }}} The "scale=3" command notifies {{{bc}}} that three digits of precision after the decimal point are required. If you are trying to compare floating point numbers, be aware that a simple ''x < y'' is not supported by all versions of {{{bc}}}. Alternatively, you could use this: {{{ if [[ $(bc <<< "1.4 - 2.5") = -* ]]; then echo "1.4 is less than 2.5." fi }}} This example substracts 2.5 from 1.4, and checks the sign of the result. If it is negative, the former number is less than the latter. {{{awk}}} can be used for calculations, too: {{{ $ awk 'BEGIN {printf "%.3f\n", 10 / 3}' /dev/null 3.333 }}} There is a subtle but important difference between the {{{bc}}} and the {{{awk}}} solution here: {{{bc}}} reads commands and expressions ''from standard input''. {{{awk}}} on the other hand evaluates the expression as ''part of the program''. Expressions on standard input are ''not'' evaluated, i.e. {{{echo 10/3 | awk '{print $0}'}}} will print {{{10/3}}} instead of the evaluated result of the expression. This explains why the example uses {{{/dev/null}}} as an input file for {{{awk}}}: the program evaluates the {{{BEGIN}}} action, evaluating the expression and printing the result. Afterwards the work is already done: it reads its standard input, gets an end-of-file indication, and terminates. If no file had been specified, {{{awk}}} would wait for data on standard input. Newer versions of KornShell93 have built-in floating point arithmetic, together with mathematical functions like {{{sin()}}} or {{{cos()}}} . |
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