Ejercicios 12f-h

exercises/ex12/false

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+#!/usr/bin/env python
+# Exercise 12h
+# false command
+
+import sys
+
+sys.exit(1)

exercises/ex12/tail

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+#!/usr/bin/env python
+# Exercise 12f
+# tail command
+
+import sys
+import argparse
+from pathlib import Path
+
+parser = argparse.ArgumentParser()
+parser.add_argument("stream", default=sys.stdin, nargs="*")
+parser.add_argument("-v", "--verbose", action="store_true")
+parser.add_argument("-n", "--lines", default="10", type=str)
+args = parser.parse_args()
+res = []
+
+
+def intonum(n):
+    try:
+        return abs(int(n))
+    except ValueError:
+        print(f"tail: el número de líneas no es válido: «{n}»")
+        sys.exit(1)
+
+
+def getlines(lines, n):
+    lines = list(map(lambda l: l.rstrip(), lines))
+    num = intonum(n)
+    if n[0] == "+":
+        return lines[num-1:]
+    return lines[-num:]
+
+
+if isinstance(args.stream, list):
+    for path in args.stream:
+        lines = Path(path).open().readlines()
+        header = [""] if len(res) != 0 else []
+        if args.verbose:
+            header += [f"==> {path} <=="]
+        res += header + getlines(lines, args.lines)
+else:
+    lines = args.stream.readlines()
+    header = ["==> entrada estándar <=="] if args.verbose else []
+    res += header + getlines(lines, args.lines)
+
+print("\n".join(res))

exercises/ex12/yes

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+#!/usr/bin/env python
+# Exercise 12g
+# yes command
+
+import argparse
+
+parser = argparse.ArgumentParser()
+parser.add_argument("words", nargs="*", type=str, default=["y"])
+args = parser.parse_args()
+
+while True:
+    print(" ".join(args.words))