5 ms·

Throw this in your ~/bin as a script named math: #!/bin/sh scale=4 # results will print to the 4th decimal echo "scale=$scale; $@" | bc -l Now you can d

Throw this in your ~/bin as a script named math: #!/bin/sh scale=4 # results will print to the 4th decimal echo "scale=$scale; $@" | bc -l Now you can do math. $ math '1+1' 2 $ math '2/3' .6666 This is especially useful in shell scripts with interpolated variables: x=10 x=`math $x - 1`

xelxebar 9y ago
Alternatively, you could use an alias: # .bashrc alias bc='bc --mathlib' and a .bcrc file: # .bcrc scale = 4 Actually, this is what my .bcrc looks like: scale = 39 k_c = 299792458 # Speed of Light k_g = 6.67384 * 10^-11 # Gravitation k_atm = 100325 # Atmospheric pressure k_h = 6.62606957 * 10^-34 # Planck's constant k_hbar = 1.054571726 * 10^-34 # H Bar k_mu = 1.256637061 * 10^-6 # Vacuum permeability k_ep = 8.854187817 * 10^-12 # Vacuum permittivity k_epsilon = 8.854187817 * 10^-12 # Vacuum permittivity k_e = 1.602176565 * 10^-19 # Elementary charge k_coulomb = 8.987551787 * 10^9 # Coulomb's constant k_me = 9.10938294 * 10^-31 # Rest mass of an electron k_mp = 1.672621777 * 10^-27 # Rest mass of a proton k_n = 6.02214129 * 10^23 # Avogadro's number k_b = 1.3806488 * 10^-23 # Boltzmann's constant k_r = 8.3144621 # Ideal gas constant k_si = 5.670373 * 10^-8 # Stefan-Boltzmann constant k_sigma = 5.670373 * 10^-8 # Stefan-Boltzmann constant k_mt = 5.97219^24 # Mass of Earth (Tierra) k_rt = 6.371 * 10^6 # Mean radius of Earth (Tierra) pi = 3.1415926535897932384626433832795028841968 # requires --mathlib define t(x) { return s(x)/c(x); } define as(x) { return 2*a(x/(1+sqrt(1-x^2))); } define ac(x) { return 2*a(sqrt(1-x^2)/(1+x)); } define at(x) { return a(x); } define csc(x) { return 1/s(x); } define sec(x) { return 1/c(x); } define cot(x) { return c(x)/s(x); }
- schoen 9y ago
  It's not nearly as flexible as bc overall, but GNU units has lots more constants built-in and also trig functions. I checked and it has all of the ones that you mentioned, sometimes under slightly different names. I was surprised that e is defined the elementary charge rather than Euler's constant!
  - majewsky 9y ago
    units(1) is my go-to calculator for everything. Really nice tool. I recommend alias units="units --verbose" because the verbose output is much less ambiguous.
    - schoen 9y ago
      Nice, thanks for the suggestion.
chubot 9y ago
That might be useful if you want floating point math, but most shell scripts can just use the integer math in shell: $ x=10 $ echo $((x - 1)) 9 Though if I need to do a floating point calculation at the shell, I start python or R, which both have their own interactive shells (with the same readline interface, which I like).

xelxebar 9y ago

Alternatively, you could use an alias: # .bashrc alias bc='bc --mathlib' and a .bcrc file: # .bcrc scale = 4 Actually, this is what my .bcrc looks like: scale = 39 k_c = 299792458 # Speed of Light k_g = 6.67384 * 10^-11 # Gravitation k_atm = 100325 # Atmospheric pressure k_h = 6.62606957 * 10^-34 # Planck's constant k_hbar = 1.054571726 * 10^-34 # H Bar k_mu = 1.256637061 * 10^-6 # Vacuum permeability k_ep = 8.854187817 * 10^-12 # Vacuum permittivity k_epsilon = 8.854187817 * 10^-12 # Vacuum permittivity k_e = 1.602176565 * 10^-19 # Elementary charge k_coulomb = 8.987551787 * 10^9 # Coulomb's constant k_me = 9.10938294 * 10^-31 # Rest mass of an electron k_mp = 1.672621777 * 10^-27 # Rest mass of a proton k_n = 6.02214129 * 10^23 # Avogadro's number k_b = 1.3806488 * 10^-23 # Boltzmann's constant k_r = 8.3144621 # Ideal gas constant k_si = 5.670373 * 10^-8 # Stefan-Boltzmann constant k_sigma = 5.670373 * 10^-8 # Stefan-Boltzmann constant k_mt = 5.97219^24 # Mass of Earth (Tierra) k_rt = 6.371 * 10^6 # Mean radius of Earth (Tierra) pi = 3.1415926535897932384626433832795028841968 # requires --mathlib define t(x) { return s(x)/c(x); } define as(x) { return 2*a(x/(1+sqrt(1-x^2))); } define ac(x) { return 2*a(sqrt(1-x^2)/(1+x)); } define at(x) { return a(x); } define csc(x) { return 1/s(x); } define sec(x) { return 1/c(x); } define cot(x) { return c(x)/s(x); }

schoen 9y ago
It's not nearly as flexible as bc overall, but GNU units has lots more constants built-in and also trig functions. I checked and it has all of the ones that you mentioned, sometimes under slightly different names. I was surprised that e is defined the elementary charge rather than Euler's constant!
- majewsky 9y ago
  units(1) is my go-to calculator for everything. Really nice tool. I recommend alias units="units --verbose" because the verbose output is much less ambiguous.
  - schoen 9y ago
    Nice, thanks for the suggestion.

chubot 9y ago

That might be useful if you want floating point math, but most shell scripts can just use the integer math in shell: $ x=10 $ echo $((x - 1)) 9 Though if I need to do a floating point calculation at the shell, I start python or R, which both have their own interactive shells (with the same readline interface, which I like).