I need to split a big text file on a certain character. I expect I am being thick about this, but [`split`][split] doesn’t quite do what I want because it includes the matching line, whereas I want to split right on the matching character.
My Python answer:
def readlines(filename, endings, chunksize=4096):
“””Returns a generator that splits on lines in a file with the given
line = ”
buf = filename.read(chunksize)
if not buf:
line = line + buf
while endings in line:
idx = line.index(endings) + len(endings)
line = line[idx:]
if __name__ == “__main__”:
import sys, os
FORMFEED = chr(12) # ASCII 12
basename = os.path.basename(sys.argv)
for num, data in enumerate(readlines(open(sys.argv), endings=FORMFEED)):
filename = basename + ‘-‘ + str(num)
This is also useful when reading data exported from some old-fashioned Mac application like [Filemaker 5][filemaker] where the line-endings are ASCII 13 not ASCII 10.
This post was inspired by [Lotus Notes][lotus] version 8.5, which is so advanced that to save a message in a file on disk you have to export it as structured text. And if you want to save a whole bunch of messages as individual files you must forget that [drag-and-drop was introduced with System 7][mactech], that would be too obvious.
I am trying to write a good one-liner for removing all restrictions on printing for Mac OS X 10.5. I had thought that [`sed`][sed] would be perfect for this, but I can’t arrive at a simple syntax for appending new lines that works well when pasted into a terminal window. Here’s what I ended up with:
perl -p -0 -i ‘.bak’ -e ‘s/(Policy default).*(Policy)/$1>\n\nOrder deny,allow\nAllow from all\n<\/Limit>\n<$2/s' /private/etc/cups/cupsd.conf
Rather brutal, it just guts the default policy and replaces it with the following:
Allow from all
Greg Neagle has [a useful article about printing in the enterprise][mactech]. Apple suggests [adding the network group to the local lpadmin group][ht3511], but points out that mobile users would need to be added individually. In my case most accounts are mobile accounts and we trust everyone to manage print queues on a Mac, so removing all restrictions is acceptable.
Note to self: [use screen] when doing a bunch of remote administration stuff over an SSH connection. You can tell it to log the session to a separate file, and can detach the session and log off without having the remote shell be terminated. Then later you can resume the session and haven’t lost anything.
To start a shell and log everything to a file, do
screen -L -S mysession
That drops you into a new shell, and lets you refer to that session later (in case you are ambitious and have many screen sessions running simultaneously). To detach the session type `CTRL+a` then `d`. From there you can exit cleanly. To resume the session later, type
screen -r mysession
The session history will be saved to a file named `screenlog.0` or similar in the directory where screen was first invoked.
[screen man page online] (Hmmm… looks like the hmug man pages have renamed themselves.)
I should use `screen` more often. I should also get in the habit of going through the contents of $PATH every time Mac OS X gets updated.