Stefan Sobek Blog

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find -size +10M -size -20M

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find ! -user root

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find -size +10M -exec ls -lh {} \;

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find -iname '*.jpg' -exec tar -rf bilder.tar {} \;

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find -iname '*.mp3' -fprint playlist.m3u

Find files with SUID bit set.

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find / -type f -perm +6000 -exec ls -l {}  \; > suid.list

This is an example from http://www.linux-user.de/ausgabe/2001/07/030-split/split.html:

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tar cz /home/user  | split -b95m - archiv.tgz.split.

Put together files with:

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cat  [dateiname].split.* | tar x

To replace a string in all files inside a folder you can create a bash file:

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vi replace.sh

Put inside this file:

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#!/bin/bash
for file in $(ls -1);
do
sed 's/me/you/g' $file > /tmp/dummy.txt;
mv /tmp/dummy.txt $file;
done

Save it and make it executeable (chmod 777 replace.sh)

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for file in $(ls -1);
do
mv $file $file.old
sed 's/<b>/<strong>/g' $file.old >  $file;
done

Another option is to use sed with -i command or direct editing:

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for file in $(ls -1);
do
sed -i 's/text_to_replace/text_replacement/g' $file
done

People often underestimate the usefulness of the linux-command screen.

What does screen do? Screen creates a terminal session for the actual user.

Type:

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screen

to create a terminal session.

Or type:

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screen -S <sessionname>

where <sessionname> should be replaced with your own name.

Create a new window:

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Crtl+a c

which means (Press Control and a together and after that press c)

Now we created a second window. To list all created windows in the actual session type:

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Crtl+a "

Germans have to press Shift+2 for “.

Now the two created windows will be shown:

Just choose one Window and press enter.

To quit your actual work an detach the session:

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Crtl+a d

To list all active sessions:

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screen -list

You should see a similar picture like the following:

Here you can see the name of the session: 1597.stefan

To restore the session simply type:

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screen -r stefan

Maybe you have to type the complete id with 1597.stefan if there exist another session with the same name.

When switching from Mac to Linux and vice versa, I always have to think a bit about how to use the command top and sort by CPU.

With Linux it is

top

and then press

shift+p

Mac:

top -o cpu

I hope I can remember this

The situation is as follows. You want to search recursive for a text pattern inside of each files in the directory /var/www/vhosts. Take e.g. the pattern ‘DataStructure’.

Normally you would think about the find-command and executing another command but grep itself can do the job.

grep -RHl -e ‘DataStructure’ /srv/www/vhosts

This command lists all filenames containing the text ‘DataStructure’

To list all open connections on the actual linux or mac just type the following:

lsof -i

For faster lookup without replacing IP through DNS-lookup:

lsof -i -n

Try also with root-permission for more files:

sudo lsof -i -n

Now you can easily spot programs connecting to the internet an dump the tcp-data with tcpdump.

For example dumping data from tcp-port 80 to a file called test.pcap:

tcpdump -w test.pcap tcp port 80

Now show the file:

tcpdump -nnr test.pcap

or

tcpdump -ttttnnr test.pcap

for timestamp information

Normally it is not ab problem to convert a CMYK picture to a RGB picture with Photoshop. But what do you do if you have e.g. thousands of high quality pictures, and you want to convert these so RGB? With Linux you can easily convert your files.

All you need is

• ImageMagick
• RGB Color profile e.g. ColorMatchRGB.icc or AdobeRGB1998.icc
• CMYK Color profile e.g. USWebCoatedSWOP.icc (can be downloaded on adobe website)

Installing ImageMagick and downloading the color profiles can not be explained here.

Now to convert picture called cmyk.jpg to rgb simply enter the following command:

convert -profile /pfad/zum/profil/USWebCoatedSWOP.icc \ -profile /pfad/zum/profil/ColorMatchRGB.icc cmyk.jpg rgb.jpg

For not writing the the whole line for each file create a bash-script:

#!/bin/bash

cmyk_profile=”/pfad/zum/profil/USWebCoatedSWOP.icc”

rgb_profile=”/pfad/zum/profil/ColorMatchRGB.icc”

ifile=”$1″ ofile=`basename “$ifile” .jpg`”_rgb.jpg”

convert -profile “$cmyk_profile” -profile “$rgb_profile” “$ifile” “$ofile”

Save this script as cmyk2rgb.sh and make it executeable with

chmod +x cmyk2rgb.sh

Now you can call this via:

./cmxk2rgb.sh bild.jpg

And a file called bild_rbb.jpg will be created.

Now other fine things are possible like find all files with ending .jpg and convert them to rgb:

  for i in *jpg;
  do
    ./cmyk2rgb.sh "$i";
  done