Bash builtin calculations support only INTEGERS!<\/p>\n\n\n\n
The shell allows arithmetic expressions to be evaluated, under certain circumstances (see the let<\/strong> and declare<\/strong> builtin commands, the ((<\/strong> compound command, and Arithmetic<\/strong> Expansion<\/strong>). Evaluation is done in fixed-width integers with no check for overflow, though division by 0 is trapped and flagged as an error. The operators and their precedence, associativity, and values are the same as in the C language. <\/p>from $ man bash<\/cite><\/blockquote>\n\n\n\n
Division in bash<\/strong> – lets divide 5 with 2 and see what result we get.<\/p>\n\n\n\n
$ let x=5\/2\n$ echo $x\n2<\/strong>\n<\/pre>\n\n\n\nMultiplication<\/strong> in bash<\/p>\n\n\n\n
$ let x=5*2\n$ echo $x\n10<\/strong><\/pre>\n\n\n\nAddition<\/strong> in bash, increment variable by one<\/p>\n\n\n\n
$ let x=5+2\n$ echo $x\n7<\/strong>\n$ let x++\n8<\/strong><\/pre>\n\n\n\nSubtraction<\/strong> in bash \/ decrement variable by one<\/p>\n\n\n\n
$ let x=5-2\n$ echo $x\n3<\/strong>\n$ let x-- \n2<\/strong><\/pre>\n\n\n\nComparing floating point numbers<\/strong> in bash<\/strong><\/p>\n\n\n\n
Bash sucks in floating point number comparison. <\/p>\n\n\n\n
Try these out as an example:<\/p>\n\n\n\n
$ x=2.5<\/strong>;y=3;if [ $x ><\/strong> $y ]; then echo \"x is greater than y\"; else echo \"x is smaller than y\";fi \nx is greater<\/strong> than y\n\n$ x=5.5<\/strong>;y=3;if [ $x -gt $y ]; then echo \"x is greater than y\"; else echo \"x is smaller than y\";fi \nbash error<\/strong> - integer expected (evaluates false) \nx is smaller<\/strong> than y<\/pre>\n\n\n\nTo overcome the limitation use simple function and awk in your bash script. <\/p>\n\n\n\n
Sample script test.sh<\/strong> containing the awk<\/strong> part in a re-usable function named float<\/strong> and also usage example in the end.<\/p>\n\n\n\n
#!\/bin\/bash \n \n# this function helps to compare floating point numbers \nfloat() { \n if [ $# -ne 2 ]; then \n \n echo \"incorrect number of arguments\" \n exit 1 \n \n else \n \n # will give both floats to awk as variables and let the awk do the comparison \n awk -v f1=${1} -v f2=${2} 'BEGIN{ if (f1<f2) print \"less\"; if (f1==f2) print \"equal\"; if (f1>f2) print \"more\"; }' \n \n fi \n} \n \n \nif [ \"`float ${1} ${2}`\" = \"less\" ];then \n echo \"${1} is less than ${2}\" \nelif [ \"`float ${1} ${2}`\" = \"more\" ];then \n echo \"${1} is greater than ${2}\" \nelse \n echo \"${1} is equal to ${2}\" \nfi\n \n\n<\/pre>\n\n\n\nInvoking the script:<\/p>\n\n\n\n
$ chmod 700 test.sh \n$ .\/test.sh 3 5 \n3 is less than 5 \n$ .\/test.sh 5 3.5 \n5 is greater than 3.5 \n$ .\/test.sh 2.5678734 2.56787 \n2.5678734 is greater than 2.56787 \n$ .\/test.sh 2.5638734 2.56787 \n2.5638734 is less than 2.56787\n<\/pre>\n\n\n\nWorks as a charm!<\/p>\n\n\n\n
Check also how to calculate pi in bash<\/a>.<\/p>\n\n\n\n