Watch a directory and tail all files

kitsune

@@ -0,0 +1,64 @@
+#!/usr/bin/python3
+
+import datetime
+import os
+import sys
+import time
+
+class WatchedFile:
+    def __init__(self, name):
+        self.name = name
+        self.reopen()
+
+    def reopen(self):
+        self.fd = open(self.name, errors='replace')
+        self.fileno = self.fd.fileno()
+        self.last_ts = 0
+
+def format_ts(ts_ns):
+    return datetime.datetime.fromtimestamp(ts_ns / 1E9).strftime("%H:%M:%S.%f")
+
+def watch(dir):
+    os.chdir(dir)
+    last_ts = 0
+    watched_files = {}
+    filename_length = 0
+    while True:
+        # are there new files?
+        st = os.stat(".")
+        if st.st_mtime_ns > last_ts:
+            last_ts = st.st_mtime_ns
+            for de in os.scandir("."):
+                if de.is_file():
+                    if de.name not in watched_files:
+                        watched_files[de.name] = WatchedFile(de.name)
+                        if len(de.name) > filename_length:
+                            filename_length = len(de.name)
+
+        # has any of the files changed
+        for f in watched_files.values():
+            # XXX - we should also detect replaced files. 
+            st = os.stat(f.fileno)
+            try:
+                stf = os.stat(f.name)
+                if stf.st_ino != st.st_ino:
+                    f.reopen()
+            except FileNotFoundError:
+                # ignore,
+                # or maybe remove from watched_files?
+                # or just mark as deleted?
+                pass
+            if st.st_mtime_ns > f.last_ts:
+                f.last_ts = st.st_mtime_ns
+                new_content = f.fd.read()
+                lines = new_content.split("\n")
+                if lines[-1] == "":
+                    lines.pop()
+                for ln in lines:
+                    print(f"{f.name:{filename_length}}", format_ts(f.last_ts), ln)
+        time.sleep(0.1)
+
+if __name__ == "__main__":
+    dir = sys.argv[1] if len(sys.argv) > 1 else "."
+
+    watch(dir)