Define a quick calculator function

? () { echo "$*" | bc -l; }

defines a handy function for quick calculations from cli. once defined: ? 10*2+3

Sample Output

23?

By: fizz

2009-06-28 20:15:30

bc echo bash bc function calc bc -l

2 Alternatives + Submit Alt

Define a quick calculator function

POSIX compliant arithmetic evaluation. = 10*2+3 Show Sample Output
This is sample output - yours may be different.
```
23
```
3

=() { echo $(($*)); }

xlz · 2013-05-03 04:27:07 4
Define a quick calculator function

Same functionality without using bash functions. Show Sample Output
This is sample output - yours may be different.
```
$ ? 3+4/2
5
```
0

alias ?=concalc

boynux · 2014-01-02 01:46:44 5

What Others Think

Another way to do that would be: ? () { let myresult="$*" ; echo $myresult; } That would avoid changing context (launching a new process, that's what "bc" is) and would be much faster if you are using the calculations in some loop or whatever. To ensure that, I made a quick test: I defined "?" as my function, and "x" as your function, and measured their times for a simple compound calculation: time ( for a in {0..999}; do ? "($a*$a-$a)/($a+$a+1)" > /dev/null ; done ) real 0m0.767s user 0m0.624s sys 0m0.144s time ( for a in {0..999}; do x "($a*$a-$a)/($a+$a+1)" > /dev/null ; done ) real 0m6.777s user 0m1.544s sys 0m4.548s Of course, it might be that you would miss some functionality for advanced calculations using the internal shell syntax instead of bc. But then again, bc (-l or not) has its limitations: you can't use it for non-integer exponentials, that is: echo "2^(1/3)" | bc -l Runtime warning (func=(main), adr=9): non-zero scale in exponent I would recommend installing the "concalc" package if you need better mathematical evaluations in shell commands: echo "2^(1/3)" | concalc 1.25992104989487316

Patola · 717 weeks and 5 days ago

sweet! many uses for this, also thanks for concalc...

wires · 717 weeks and 4 days ago

I prefer the Pari calculator which in this situation can be invoked as "gp -q". It gives you tons of functions and an obscene number of decimal points. For some reason when I try to run the "?" function defined above I just get "bash: z: command not found" and for "help ?" I get "help: no help topics match `z'". Any ideas why?

dstahlke · 717 weeks and 4 days ago

@dstahlke this is because you have a file named z in the current directory, the shell expands ? to z, so you get this error message

unixmonkey4488 · 717 weeks and 4 days ago

As long as I've been bash'ing, I didn't know you could use ? as a function name. Thanks for the example for that, even if I don't use the calculator function! :)

hal0thane · 717 weeks and 3 days ago

Is it actually necessary to define a function for "bc"? It is simple enough to do this: <<< "x=1; y=2; p=3*x+2*y; p" bc -l

mpb · 717 weeks and 3 days ago

you can use bash format for very simple calculations like echo $[ 1*2 + 3 ] 5

elementa13 · 717 weeks and 3 days ago

bc <<< 10*2+3

mpb · 717 weeks ago

Here is what I have defines: ? for bash arithmetic, calc for awk arithmetic, and a here-string for bc -l arithmetic: # bash arithmetic function ? { echo $[$*] } # awk arithmetic (floating point result) function calc(){ awk "BEGIN{ print $* }" ;} bc -l<<<3/7