How to solve a linear system in Linux shell?

Question

Does anyone know of a Linux command that reads a linear system of equations from its standard input and writes the solution (if exists) in its standard output?

I want to do something like this:

generate_system | solve_system

Answer 1

You can probably write your own such command using this package.

Answer 2

This is an old question, but showed up in my searches for this problem, so I'm adding an answer here.

I used maxima's solve function. Wrangling the input/output to/from maxima is a bit of a challenge, but can be done.

1. prepare the system of equations as a comma-separated list -- for a example, EQs="C[1]+C[2]=1,C[1]-C[2]=2". I wanted a solution for an unknown number of variables, so I used C[n], but you can use variable names.
2. prepare a list of variables you wish to solve for -- EQ_VARS="C[1],C[2]"
3. Maxima will echo all inputs, use line wrap, and return a solution in the form [C[1]=...,C[2]=..]. We need to resolve all of these.

Taken together, this becomes

OUT_VALS=( \
    $(maxima --very-quiet \
        --batch-string="display2d:false\$linel:9999\$print(map(rhs,float(solve([$EQs],[$EQ_VARS]))[1]))\$" \
        | tail -n 1 \
        | tr -c '0-9-.e' ' ') )

which will place the solution values into the array $OUT_VALS.

Note that this only properly handles that Maxima output if your problem is correctly constrained -- if you have zero, or more than one solution, the output will not be parsed correctly.