Initial commit

Dockerfile

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+FROM alpine
+RUN apk add --no-cache bash python3
+RUN adduser -D user
+USER user
+ADD runall.py /
+CMD ["python3", "/runall.py"]

README.md

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+How to run:
+
+```
+docker image build --quiet --tag runall-image .
+docker container run --tty --rm --read-only runall-image
+```

runall.py

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+from itertools import product
+import string
+import subprocess
+
+
+def check_pair(script, instr, outstr):
+    result = subprocess.run(
+        ["/usr/bin/env", "bash", "-c", script],
+        input=instr.encode(),
+        capture_output=True,
+    )
+    return result.returncode == 0 and result.stdout == outstr.encode()
+
+
+def check_pairs(script, pairs):
+    for pair in pairs:
+        if not check_pair(script, *pair):
+            return False
+    return True
+
+
+def find_script(pairs, max_length):
+    candidates = []
+    total_options = len(string.printable) ** max_length
+    current_option = 0
+
+    for length in range(max_length + 1):
+        for letters in product(string.printable, repeat=length):
+            if current_option % 1000 == 0:
+                print(f"Progress: {current_option}/{total_options}")
+
+            script = "".join(letters)
+
+            if check_pairs(script, pairs):
+                print("> Found candidate:", script)
+                candidates.append(script)
+
+            current_option += 1
+
+    print("Candidates:", candidates)
+
+
+if __name__ == '__main__':
+    # Identity
+    print("\nSearching for identity")
+    find_script((
+        ("1", "1"),
+        ("2", "2"),
+        ("3", "3"),
+    ), max_length=2)
+
+    # Successor
+    print("\nSearching for successor")
+    find_script((
+        ("1", "2"),
+        ("2", "3"),
+        ("3", "4"),
+    ), max_length=5)