Floating-point arithmetic in UNIX shell script
I believe you should use : bc
For example:
echo "scale = 10; 123.456789/345.345345" | bc
(It's the unix way: each tool specializes to do well what they are supposed to do, and they all work together to do great things. don't emulate a great tool with another, make them work together.)
Output:
.3574879198
Or with a scale of 1
instead of 10
:
echo "scale = 1; 123.456789/345.345345" | bc
Output:
.3
Note that this does not perform rounding.
I highly recommand switching to awk if you need to do more complex operations, or perl for the most complex ones.
ex: your operations done with awk:
# create the test file:printf '1.5493482,3.49384,33.284732,23.043852,2.2384,12.1,13.4,...\n' > somefileprintf '3.384,3.282342,23.043852,2.23284,8.39283,14.1,15.2,...\n' >> somefile# do OP's calculations (and DEBUG print them out!)awk -F',' ' # put no single quote in here... even in comments! you can instead print a: \047 # the -F tell awk to use "," as a separator. Thus awk will automatically split lines for us using it. # $1=before first "," $2=between 1st and 2nd "," ... etc. function some_awk_function_here_if_you_want() { # optionnal function definition # some actions here. you can even have arguments to the function, etc. print "DEBUG: no action defined in some_awk_function_here_if_you_want yet ..." } BEGIN { rem="Optionnal START section. here you can put initialisations, that happens before the FIRST file-s FIRST line is read" } (NF>=8) { rem="for each line with at least 8 values separated by commas (and only for lines meeting that condition)" calc1=($2 - $7) calc2=($3 * $2) calc3=($2 - $1) calc4=($2 + $8) # uncomment to call this function :(ex1): # some_awk_function_here_if_you_want # uncomment to call this script:(ex2): # cmd="/path/to/some/script.sh \"" calc1 "\" \"" calc2 "\" ..." ; rem="continued next line" # uncomment to call this script:(ex2): # system(cmd); close(cmd) line_no=(FNR-1) # ? why -1? . FNR=line number in the CURRENT file. NR=line number since the beginning (NR>FNR after the first file ...) print "DEBUG: calc1=" calc1 " , calc2=" calc2 " , calc3=" calc3 " , calc4=" calc4 " , line_no=" line_no print "DEBUG fancier_exemples: see man printf for lots of info on formatting (%...f for floats, %...d for integer, %...s for strings, etc)" printf("DEBUG: calc1=%d , calc2=%10.2f , calc3=%s , calc4=%d , line_no=%d\n",calc1, calc2, calc3, calc4, line_no) } END { rem="Optionnal END section. here you can put things that need to happen AFTER the LAST file-s LAST line is read" } ' somefile # end of the awk script, and the list of file(s) to be read by it.
What about this?
calc=$(echo "$String2 + $String8"|bc)
This will make bc
to add the values of $String2 and $String8 and saves the result in the variable calc
.
If you don't have the "bc" you can jast use 'awk' :
calc=$(echo 2.3 4.6 | awk '{ printf "%f", $1 + $2 }')