Commands by olorin (9)

  • Configures screen to always display the clock in the last line (has to be configured only once). After that you not only have got the possibility to detach sessions and run them in background, but also have got a nice clock permanently on your screen.


    4
    echo 'hardstatus alwayslastline " %d-%m-%y %c:%s | %w"' >> $HOME/.screenrc; screen
    olorin · 2011-02-16 08:04:56 2
  • If you provide the option -t to the script command and redirect stderr into a file, the timing information on what is going on on the terminal, is also stored. You can replay the session via the scriptreplay command, where you can also provide a speedup factor (see the man page for details). Great for demonstration purposes ...


    23
    script -t /tmp/mylog.out 2>/tmp/mylog.time; <do your work>; <CTRL-D>; scriptreplay /tmp/mylog.time /tmp/mylog.out
    olorin · 2011-01-19 07:16:30 18
  • As an alternative to using an additional grep -v grep you can use a simple regular expression in the search pattern (first letter is something out of the single letter list ;-)) to drop the grep command itself. Show Sample Output


    72
    ps aux | grep [p]rocess-name
    olorin · 2009-08-13 05:44:45 19
  • Within /proc and /sys there are a lot of subdirectories, which carry pseudofiles with only one value as content. Instead of cat-ing all single files (which takes quite a time) or do a "cat *" (which makes it hard to find the filename/content relation), just grep recursively for . or use "grep . /blabla/*" (star instead of -r flag). For better readability you might also want to pipe the output to "column -t -s : ". Show Sample Output


    4
    grep -r . /sys/class/net/eth0/statistics
    olorin · 2009-08-05 08:20:39 2
  • Get the name of the parent command. This might be helpful, if you need to react on that information. E. g. a script called directly via ssh has got sshd as parent, manually invoked the parent process will probably be bash


    4
    ps -o comm= -p $(ps -o ppid= -p $$)
    olorin · 2009-08-03 07:41:21 4
  • If you are doing some tests which require reboots (e. g. startup skripts, kernel module parameters, ...), this is very time intensive, if you have got a hardware with a long pre-boot phase due to hardware checks. At this time, kexec can help, which only restarts the kernel with all related stuff. First the kernel to be started is loaded, then kexec -e jumps up to start it. Is as hard as a reboot -f, but several times faster (e. g. 1 Minute instead of 12 on some servers here). Show Sample Output


    21
    /sbin/kexec -l /boot/$KERNEL --append="$KERNELPARAMTERS" --initrd=/boot/$INITRD; sync; /sbin/kexec -e
    olorin · 2009-08-03 07:36:49 13
  • Instead of calculating the offset and providing an offset option to mount, let lomount do the job for you by just providing the partition number you would like to loop mount.


    4
    lomount -diskimage /path/to/your/backup.img -partition 1 /mnt/foo
    olorin · 2009-07-22 11:32:52 15
  • You got some results in two variables within your shell script and would like to find the differences? Changes in process lists, reworked file contents, ... . No need to write to temporary files. You can use all the diff parameters you'll need. Maybe anything like $ grep "^>" is helpful afterwards.


    27
    diff <(echo "$a") <(echo "$b")
    olorin · 2009-07-15 07:26:23 8
  • Let dd use direct I/O to write directly to the disk without any caching. You'll encounter very different results with different block sizes (try with 1k, 4k, 1M, ... and appropriate count values).


    0
    time dd if=/dev/zero of=blah.out oflag=direct bs=256M count=1
    olorin · 2009-07-15 07:17:32 2

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remove execute bit only from files. recursively

Exclude svn directories with grep
exclude-dir option requires grep 2.5.3

fix flash video (flv) file (ffmpeg)
Rebuild flv files that are broken (can't seek). This method probably works for other video/audio formats that can become broken in the same way.

Remote screenshot
Say if you're logged into a remote system via ssh and this system has an x window system, but yet you still want a screen shot of what's going on graphically. This will do it for you. :-)

command shell generate random strong password
shell generate random strong password

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

grab all commandlinefu shell functions into a single file, suitable for sourcing.
Much simpler but not as many features as the alternative.

List latest 5 modified files recursively
The output format is given by the -printf parameter: %T@ = modify time in seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Mandatory, hidden in the end. %TY-%Tm-%Td %TH:%TM:%.2TS = modify time as YYYY-MM-DD HH:MM:SS. Optional. %p = file path Refer to http://linux.die.net/man/1/find for more about -printf formatting. ------------------------ sort -nr = sort numerically and reverse (higher values - most recent timestamp - first) head -n 5 = get only 5 first lines (change 5 to whatever you want) cut -f2- -d" " = trim first field (timestamp, used only for sorting) ------------------------ Very useful for building scripts for detecting malicious files upload and malware injections.

Puts every word from a file into a new line
Simply translates whitespace to newlines. Could be enhanced to compress out extra newlines, but that might be better handled in the next tool down the pipe, with eg uniq(1).

Find usb device in realtime
Using this command you can track a moment when usb device was attached.


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