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Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.
Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):
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This command will show the 20 processes using the most CPU time (hungriest at the bottom).
You can see the 20 most memory intensive processes (hungriest at the bottom) by running:
ps aux | sort +3n | tail -20
Or, run both:
echo "CPU:" && ps aux | sort +2n | tail -20 && echo "Memory:" && ps aux | sort +3n | tail -20
This command will tell you the 20 biggest directories starting from your working directory and skips directories on other filesystems. Useful for resolving disk space issues.
See man vmstat for information about the statistics.
This does the same thing without the timestamp:
This truncates any lines longer than 80 characters. Also useful for looking at different parts of the line, e.g. cut -b 50-100 shows columns 50 through 100.
Suppose you made a backup of your hard disk with dd:
dd if=/dev/sda of=/mnt/disk/backup.img
This command enables you to mount a partition from inside this image, so you can access your files directly.
Substitute PARTITION=1 with the number of the partition you want to mount (returned from sfdisk -d yourfile.img).
This command is much quicker than the alternative of "sort | uniq -c | sort -n".
with discard wilcards in bash you can "tail" newer logs files to see what happen, any error, info, warn...
The pipe to head removes the listing of . as the largest directory.
In this case, I'm keeping an eye on /var/log/messages, but of course any file will do. When I'm following a file, I generally don't want to see anything other than what has been added due to the command or service I've executed. This keeps everything clean and tidy for troubleshooting.
Useful to e.g. keep an eye on several logfiles.
It displays, last 15 yum operations (in last operation as first row order) with its dates. Change 15 to any number of operations you need to display or remove "| tac" to see it in reverse order (last operation as last row)
The hyphen tells vim to open from STDOUT - saves having to create temporary files.
tail would be considered dull, but pair this with being able to push out unix commands over ARD, and life gets easier. (Same can be said for my TimeMachine scrape command, http://xrl.us/begrzb)
While they are few config options and even fewer useful details regarding what actually is being sent by the time machine 'backupd' process, this can at least tell you its doing something, how much it's doing, and exactly how often. Via macosxhints, http://xrl.us/begrwa, which in turn was via comments
If you have this command in your history, you can always re-run it and have it reference the latest file.
The glob matches all timestamped files and then the resulting array is sorted by modification time (m) and then the first element in the sorted array is chosen (the latest)
List top 20 IP from which TCP connection is in SYN_RECV state.
Useful on web servers to detect a syn flood attack.
Replace SYN_ with ESTA to find established connections
tells you the number of lines in said file, and then tail the last 100 lines ( or how many are messed up) then u take the total amount of lines and then subract the 100 or so lines u DONT WANT, then do a head -n $new_number and then redirect it to new file.db
Use this command to see logs update in real time
Use the aliased command 'nsl'
This command opens the latest, most current rotating apache access log for visual analysis and inspection. Run this command from the apache log directory. For error logs, replace access_log with error_log.
This is useful for keeping an eye on an error log while developing. The !^ pulls the first arg from the previous command (which needs to be run in a sub-shell for this shortcut to work).
This uses awk to grab the IP address from each request and then sorts and summarises the top 10.