How to compare two floating point numbers in Bash

Question

I am trying hard to compare two floating point numbers within a bash script  I have to variables  e g  let num1 3 17648e-22 let num2 1 5  Now  I just want do a simple comparison of these two numbers  st  echo  quot  num1  lt   num2 quot    bc  if    st -eq 1   then   echo -e  quot  num1  lt   num2 quot  else   echo -e  quot  num1  gt    num2 quot  fi  Unfortunately  I have some problems with the right treatment of the num1 which can be of the  quot e-format quot

User · Answer

I was posting this as an answer to https://stackoverflow.com/a/56415379/1745001 when it got closed as a dup of this question so here it is as it applies here too:

For simplicity and clarity just use awk for the calculations as it's a standard UNIX tool and so just as likely to be present as bc and much easier to work with syntactically.

For this question:

$ cat tst.sh
#!/bin/bash

num1=3.17648e-22
num2=1.5

awk -v num1="$num1" -v num2="$num2" '
BEGIN {
    print "num1", (num1 < num2 ? "<" : ">="), "num2"
}
'

$ ./tst.sh
num1 < num2

and for that other question that was closed as a dup of this one:

$ cat tst.sh
#!/bin/bash

read -p "Operator: " operator
read -p "First number: " ch1
read -p "Second number: " ch2

awk -v ch1="$ch1" -v ch2="$ch2" -v op="$operator" '
BEGIN {
    if ( ( op == "/" ) && ( ch2 == 0 ) ) {
        print "Nope..."
    }
    else {
        print ch1 '"$operator"' ch2
    }
}
'

$ ./tst.sh
Operator: /
First number: 4.5
Second number: 2
2.25

$ ./tst.sh
Operator: /
First number: 4.5
Second number: 0
Nope...

User · Answer

awk and tools like it  I m staring at you sed     should be relegated to the dustbin of old projects  with code that everyone is too afraid to touch since it was written in a read-never language   Or you re the relatively rare project that needs to prioritize CPU usage optimization over code maintenance optimization    in which case  carry on   If not  though  why not instead just use something readable and explicit  such as python  Your fellow coders and future self will thank you  You can use python inline with bash just like all the others   num1 3 17648E-22 num2 1 5 if python -c  exit 0 if  num1  lt   num2 else 1    then     echo  yes   num1  lt   num2  else     echo  no   num1  gt    num2  fi

User · Answer

Using bashj  https   sourceforge net projects bashj     a bash mutant with java support  you just write  and it IS easy to read       usr bin bashj    java static int doubleCompare double a double b   return  a gt b    1    a lt b    -1   0       bashj num1 3 17648e-22 num2 1 5 comp j doubleCompare  num1  num2  if    comp    0     then echo  Equal    fi if    comp    1     then echo   num1  gt   num2    fi if    comp    -1     then echo   num2  gt   num1    fi   Of course bashj bash java hybridation offers much more

User · Answer

Pure bash solution for comparing floats without exponential notation  leading or trailing zeros   if     FOO     -eq   BAR        amp  amp      FOO       gt    BAR              FOO     -gt   BAR        then   echo    FOO   gt    BAR    else   echo    FOO   lt     BAR    fi   Order of logical operators matters  Integer parts are compared as numbers and fractional parts are intentionally compared as strings  Variables are split into integer and fractional parts using this method   Won t compare floats with integers  without dot

User · Answer

beware when comparing numbers that are package versions  like checking if grep 2 20 is greater than version 2 6     awk  BEGIN   print  2 20  gt   2 6     YES     NO     NO    awk  BEGIN   print  2 2  gt   2 6     YES     NO     NO    awk  BEGIN   print  2 60    2 6     YES     NO     YES   I solved such problem with such shell awk function     get version of GNU tool toolversion         local prog   1  operator   2  value   3  version      version    prog --version   awk   print  NF  exit         awk -vv1   version  -vv2   value   BEGIN           split v1  a         split v2  b                 if  a 1     b 1                 exit  a 2    operator  b 2     0   1                   else               exit  a 1    operator  b 1     0   1                     if toolversion grep   gt    2 6  then      do something awesome fi

User · Answer

num1 0 555 num2 2 555   if    echo   num1 gt  num2  bc  -eq 1    then        echo   num1 is greater then  num2  else        echo   num2 is greater then  num1  fi

User · Answer

How about this   D  VAL TO CHECK  1 00001  if     awk   printf  1  gt    2    1   0    lt  lt  lt    VAL TO CHECK 1    -eq 1     then     echo   VAL TO CHECK  gt   1  else     echo   VAL TO CHECK  lt  1  fi

User · Answer

This script may help where I m checking if installed grails version is greater than minimum required  Hope it helps       bin bash                                                                                           min 1 4                                                                                              current  echo   grails --version   head -n 2   awk   print  NF     cut -c 1-3                             if   1 -eq  echo    current   lt    min     bc                                                              then                                                                                                     echo  yo  you have older version of grails                                                      else                                                                                                                                                                                                                            echo  Hurray  you have the latest version   fi

User · Answer

Use korn shell  in bash you may have to compare the decimal part separately     bin ksh X 0 2 Y 0 2 echo  X echo  Y  if     X -lt  Y    then      echo  X is less than Y  elif     X -gt  Y    then      echo  X is greater than Y  elif     X -eq  Y    then      echo  X is equal to Y  fi

User · Answer

It s better to use awk for non integer mathematics  You can use this bash utility function   numCompare        awk -v n1   1  -v n2   2   BEGIN  printf   s    n1 lt n2   lt     gt        s n   n1  n2       And call it as   numCompare 5 65 3 14e-22 5 65  gt   3 14e-22  numCompare 5 65e-23 3 14e-22 5 65e-23  lt  3 14e-22  numCompare 3 145678 3 145679 3 145678  lt  3 145679

User · Answer

More conveniently  This can be done more conveniently using Bash s numeric context   if      echo   num1  gt   num2   bc -l      then       fi   Explanation  Piping through the basic calculator command bc returns either 1 or 0   The option -l is equivalent to --mathlib  it loads the standard math library   Enclosing the whole expression between double parenthesis       will translate these values to respectively true or false   Please  ensure that the bc basic calculator package is installed   This equally works for floats in scientific format  provided a capital letter E is employed  e g  num1 3 44E6

User · Answer

please check the below edited code -     bin bash  export num1  3 17648 e-22  export num2 1 5  st     echo   num1  lt   num2   bc    if    st -eq 1     then     echo -e   num1  lt   num2    else     echo -e   num1  gt    num2  fi   this works well

User · Answer

bash handles only integer maths but you can use bc command as follows     num1 3 17648E-22   num2 1 5   echo  num1  gt   num2   bc -l 0   echo  num2  gt   num1   bc -l 1   Note that exponent sign must be uppercase

User · Answer

You can use awk combined with a bash if condition  if awk  BEGIN  exit     d1   gt     d2      then     echo  quot yes quot  else      echo  quot no quot  fi

User · Answer

A solution supporting all possible notations  including the scientific notation with both uppercase and lowercase exponents  e g   12 00e4    if      bc -l  lt  lt  lt     value1 e E   lt    value2 e E       then     echo   value1 is below  value2  fi

User · Answer

Of course  if you don t need really floating-point arithmetic  just arithmetic on e g  dollar values where there are always exactly two decimal digits  you might just drop the dot  effectively multiplying by 100  and compare the resulting integers   if       10   num1       lt     10   num2          then           This obviously requires you to be sure that both values have the same number of decimal places

User · Answer

I used the answers from here and put them in a function  you can use it like this   is first floating number bigger 1 5 1 2 result      FUNCTION RETURN     Once called  echo  result will be 1 in this case  otherwise 0   The function   is first floating number bigger          number1   1      number2   2           number1     -eq   number2        amp  amp      number1       gt    number2              number1     -gt   number2            result        if     result  -eq 0    then result 1  else result 0  fi        FUNCTION RETURN    result       Or a version with debug output   is first floating number bigger          number1   1      number2   2       echo      is first floating number bigger  comparing   number1  with   number2   to check if the first one is bigger            number1     -eq   number2        amp  amp      number1       gt    number2              number1     -gt   number2            result        if     result  -eq 0    then result 1  else result 0  fi      echo      is first floating number bigger  result is    result        if     result  -eq 0    then         echo      is first floating number bigger    number1  is not bigger than   number2       else         echo      is first floating number bigger    number1  is bigger than   number2       fi        FUNCTION RETURN    result       Just save the function in a separated  sh file and include it like this      path to the new-file sh

[bash] How to compare two floating point numbers in Bash?

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