A short bash script (with a Python here doc) to extract matrices from an abaqus mtx file. The test case for this is a substructure matrix output analysis outputting the mass, stiffness and some recovery matrix rows. It assumes the matrix storage to be in dense symmetric form. Avoided unnecessary conditionals for readability. Hope it helps someon…

ReadAbaqusMtx.sh

#!/bin/sh

if [ $# = 1 ]
then
    echo "Correct call!"
else
    echo "Wrong call - quitting!"
    return
fi
echo "Preprocessing mtx files"
awk 'BEGIN{start=0} ($1~/^\*M/){start=start+1;} ($1~/^\*\*/){start=0} (start==1 && $1!~/^\*/){print}' $1|awk 'BEGIN{RS=",";ORS="\n"}{print}'|awk '(NF!=0){print}' > ./STIFFNESS.mtx
awk 'BEGIN{start=0} ($1~/^\*M/){start=start+1;} ($1~/^\*\*/){start=0} (start==2 && $1!~/^\*/){print}' $1|awk 'BEGIN{RS=",";ORS="\n"}{print}'|awk '(NF!=0){print}' > ./MASS.mtx
awk 'BEGIN{start=0;op=0} ($1~/^\*M/){start=1} (start==1 && $1~/\*\*/){print $0}' $1|cut --complement -d ' ' -f1|awk 'BEGIN{FS=".";OFS="."}(NF>=2){print}'|awk 'BEGIN{RS=",\n";ORS=" "}{print}'|awk '(NF>0){print}'|awk 'BEGIN{RS=", ";ORS=" "}{print}'|awk '(NF>0){print}' > RECOV.mtx
echo "Preprocessing mtx files done"

python <<EOF
import numpy as np
import scipy.io as io

Mv = np.loadtxt('MASS.mtx');
Kv = np.loadtxt('STIFFNESS.mtx');
R = np.loadtxt('RECOV.mtx');

print("Reading mtx arrays done")

Nelm = len(Mv);
Nelk = len(Kv);
if (Nelm!=Nelk):
	sys.exit("GIGO - Mass & Stiffness not of same length.");
Nel = Nelm;

Nd = np.int((np.sqrt(1+8*Nel)-1)/2); # Solution of Nd(Nd+1)/2-Nel = 0

M = np.zeros((Nd,Nd));
K = np.zeros((Nd,Nd));

(xi,yi) = np.tril_indices(Nd);
M[xi,yi] = Mv;
M[yi,xi] = Mv;
K[xi,yi] = Kv;
K[yi,xi] = Kv;

print("Matrix extraction done - writing mat file")
dict = {"M": M, "K": K, "R": R};
io.savemat("OUT.mat",dict);
print("Processing Over")
EOF