How to use C program directly without using files?

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I would like to use C program in SageMath. The way I do it is as follows:

    fp1='r4.txt'
    fp2='commandToRunC.txt'
    fp3='HL8results18.txt'
    F1 = open(fp1,'w')
    for j in p1:
        F1.write(chr(j+48))
    F1.write(str(' '))
    for j in p2:
        F1.write(str(j))
    F1.write(str('\n'))
    F1.close()

    F1 = open(fp2,'w')
    F1.write("./a.out ")
    F1.write(str(kk))
    F1.write(" r4.txt | awk '{print $NF}' > HL8results18.txt")
    F1.close()

    import os
    with open(fp2, 'r') as fp:
        L = fp.readline()
    cmd = L
    os.system(cmd)

This works but I need to rewrite the data in txt files r4.txt, commandToRunC.txt, HL8results18.txt each time. The computation I am doing is quite large. So I would like to not to write the results to files but use them directly in SageMath. Is there some way to do this? Thank you very much.