Implement cat command in Python

Author: Pezhman-Azizi

implement-shell-tools/cat/cat.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+import sys
+import glob
+
+def cat(files, number_all=False, number_nonblank=False):
+    line_num = 1
+    for filename in files:
+        try:
+            with open(filename, "r") as f:
+                for line in f:
+                    stripped = line.rstrip("\n")
+
+                    if number_all:
+                        print(f"{line_num:6}\t{stripped}")
+                        line_num += 1
+                    elif number_nonblank:
+                        if stripped:
+                            print(f"{line_num:6}\t{stripped}")
+                            line_num += 1
+                        else:
+                            print()
+                    else:
+                        print(stripped)
+        except FileNotFoundError:
+            print(f"cat: {filename}: No such file or directory", file=sys.stderr)
+
+def main():
+    args = sys.argv[1:]
+
+    number_all = "-n" in args
+    number_nonblank = "-b" in args
+
+    # Remove flags from args
+    files = [arg for arg in args if arg not in ("-n", "-b")]
+
+    # Expand globs like *.txt
+    expanded_files = []
+    for file in files:
+        expanded_files.extend(glob.glob(file))
+
+    if not expanded_files:
+        print("cat: missing file operand", file=sys.stderr)
+        sys.exit(1)
+
+    cat(expanded_files, number_all=number_all, number_nonblank=number_nonblank)
+
+if __name__ == "__main__":
+    main()