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?`

58
2009-06-28 20:15:30

2 Alternatives + Submit Alt

• POSIX compliant arithmetic evaluation. = 10*2+3 Show Sample Output

3
=() { echo \$((\$*)); }
· 2013-05-03 04:27:07
• Same functionality without using bash functions. Show Sample Output

0
alias ?=concalc
· 2014-01-02 01:46:44

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 · 781 weeks and 5 days ago
sweet! many uses for this, also thanks for concalc...
wires · 781 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 · 781 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 · 781 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 · 781 weeks and 4 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 · 781 weeks and 4 days ago
you can use bash format for very simple calculations like `echo \$[ 1*2 + 3 ]` 5
elementa13 · 781 weeks and 3 days ago
`bc <<< 10*2+3`
mpb · 781 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`
ShellWhisperer · 752 weeks and 4 days ago
Different calculators for different levels: bash for simplest integer operations: `echo \$[2*(3+5)]` 16 awk for floating point and powers `function ? { awk "BEGIN{ print \$* }" ;}` `? '((2+1)/7)^3.5'` 0.0515325 concalc for full scientific functions: `concalc<<<'sin(32^(1/3))'` -0.0332033464121159848 bc for high precision: `bc -l<<<3/7` .42857142857142857142 gp for number theory: gp -qf 2.6040699049291378729513930560926568818 E574964
ShellWhisperer · 752 weeks and 4 days ago
Fixing that: gp for number theory: `gp -qf` 2.6040699049291378729513930560926568818 E574964
ShellWhisperer · 752 weeks and 4 days ago
gp for number theory: `gp -qf<<<'123456! + 0.'` 2.6040699049291378729513930560926568818 E574964
ShellWhisperer · 752 weeks and 4 days ago
Now if anyone has a way to delete or modify typos in comments, please let me know.
ShellWhisperer · 752 weeks and 4 days ago
I won't be using this exact command because I don't need a specific function setup for this, but I didn't know about the bc command even though I've been using linux for many years. It's pretty nice. Thumbs up.
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What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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