commandlinefu.com is the place to record those command-line gems that you return to again and again.
Delete that bloated snippets file you've been using and share your personal repository with the world. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.
You can sign-in using OpenID credentials, or register a traditional username and password.
First-time OpenID users will be automatically assigned a username which can be changed after signing in.
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.
» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10
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,…):
Subscribe to the feed for:
perl version of "Wait for file to stop changing"
When "FileName" has not been changed for last 10 seconds, then print "DONE"
"10" in "(stat)[10]" means ctime.
One have other options like atime, mtime and others. http://perldoc.perl.org/functions/stat.html
This loop will finish if a file hasn't changed in the last 10 seconds.
.
It checks the file's modification timestamp against the clock.
If 10 seconds have elapsed without any change to the file, then the loop ends.
.
This script will give a false positive if there's a 10 second delay between updates,
e.g. due to network congestion
.
How does it work?
'date +%s' gives the current time in seconds
'stat -c %Y' gives the file's last modification time in seconds
'$(( ))' is bash's way of doing maths
'[ X -lt 10 ]' tests the result is Less Than 10
otherwise sleep for 1 second and repeat
.
Note: Clever as this script is, inotify is smarter.
This will write to TAPE (LTO3-4 in my case) a backup of files/folders. Could be changed to write to DVD/Blueray.
Go to the directory where you want to write the output files : cd /bklogs
Enter a name in bkname="Backup1", enter folders/files in tobk="/home /var/www".
It will create a tar and write it to the tape drive on /dev/nst0.
In the process, it will
1) generate a sha512 sum of the tar to $bkname.sha512; so you can validate that your data is intact
2) generate a filelist of the content of the tar with filesize to $bkname.lst
3) buffer the tar file to prevent shoe-shining the tape (I use 4GB for lto3(80mb/sec), 8gb for lto4 (120mb/sec), 3Tb usb3 disks support those speed, else I use 3x2tb raidz.
4) show buffer in/out speed and used space in the buffer
5) show progress bar with time approximation using pv
ADD :
To eject the tape :
; sleep 75; mt-st -f /dev/nst0 rewoffl
TODO:
1) When using old tapes, if the buffer is full and the drive slows down, it means the tape is old and would need to be replaced instead of wiping it and recycling it for an other backup. Logging where and when it slows down could provide good information on the wear of the tape. I don't know how to get that information from the mbuffer output and to trigger a "This tape slowed down X times at Y1gb, Y2gb, Y3gb down to Zmb/s for a total of 30sec. It would be wise to replace this tape next time you want to write to it."
2) Fix filesize approximation
3) Save all the output to $bkname.log with progress update being new lines. (any one have an idea?)
4) Support spanning on multiple tape.
5) Replace tar format with something else (dar?); looking at xar right now (https://code.google.com/p/xar/), xml metadata could contain per file checksum, compression algorithm (bzip2, xv, gzip), gnupg encryption, thumbnail, videopreview, image EXIF... But that's an other project.
TIP:
1) You can specify the width of the progressbar of pv. If its longer than the terminal, line refresh will be written to new lines. That way you can see if there was speed slowdown during writing.
2) Remove the v in tar argument cvf to prevent listing all files added to the archive.
3) You can get tarsum (http://www.guyrutenberg.com/2009/04/29/tarsum-02-a-read-only-version-of-tarsum/)
and add >(tarsum --checksum sha256 > $bkname_list.sha256) after the tee to generate checksums of individual files !
Execute commands serially on a list of hosts. Each ssh connection is made in the background so that if, after five seconds, it hasn't closed, it will be killed and the script will go on to the next system.
Maybe there's an easier way to set a timeout in the ssh options...
For use when you can't use "watch" (user-defined functions, aliases). This isn't mine - its an alternate posted in the comments by flatcap, and is the shortest and easiest to remember.
the "delay" utility is an invaluable tool for me. with gnu-screen it allows you to schedule something and have it run and output to the current terminal, unlike "at".
You can also use it like "sleep" with seconds and also with date:
delay until 13:33 friday && echo test
get it from: http://onegeek.org/~tom/software/delay/current/delay.c
(author: Tom Rothamel)
this will open a new tab in firefox for every line in a file
the sleep is removable but i found that if you have a large list of urls 50+, and no sleep, it will try to open all the urls at once and this will cause them all to load a lot slower, also depending on the ram of your system sleep gives you a chance to close the tabs before they overload your ram, removing & >2/dev/null will yield unpredictable results.
Countdown clock - Counts down from $MIN minutes to zero.
I let the date command do the maths.
This version doesn't use seq.
Cycles continuously through a string printing each character with a random delay less than 1 second. First parameter is min, 2nd is max. Example: 1 3 means sleep random .1 to .3. Experiment with different values. The 3rd parameter is the string. The sleep will help with battery life/power consumption.
cycle 1 3 $(openssl rand 100 | xxd -p)
Fans of "The Shining" might get a kick out of this:
cycle 1 4 ' All work and no play makes Jack a dull boy.'
No need to be root to do that. Relies on UPower (previously known as DeviceKit-Power).
It suspends to RAM: you always need your batteries for the RAM but it saves time as there is no need to slowly archive everything on your hard disk.
It works fine with me but if anyone has a nicer way, please contribute.