The initial setup consists of a remote server running KVM in which three virtual machines were installed using Ubuntu 16.04. Each virtual machine has one network interface bridged to a physical network interface on the remote server, so that each VM is using a different interface of the server and IP addresses were assigned accordingly.
At the end of this tutorial, you will have a kubernetes cluster that consist of one Kubernetes master and two Kubernetes nodes.
What is sed?
Sed is a stream editor which is used to perform basic text transformations on an input stream (a file or input from a pipeline) or filter strings. It permits to modify the contents of different lines in a file, based on some parameters.
For the examples shown in this article, you used the 4.2.1 version of sed as shown below:
sed --version GNU sed version 4.2.1 Copyright (C) 2009 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, to the extent permitted by law.
Sed has a syntax as follows:
sed [-options] [command] [<file(s)>]
Visualization
For the cases where you need to display the contents of a file or part of it, we can use any of the following commands:
sed 5q file1 # see the firsts 5 lines of file1 cat -n file1 | sed -n '5,6 p' # see lines 5 and 6 of file1 sed -n '1p' file1 > file2 # copy the first line of file1 to file2 sed -n '$p' file1 # show the last line of file1
Replacing strings and characters
In these cases, it is always advisable storing in another file, the results of a substitution, leaving the original file unchanged. Some examples are:
# replace strings in all lines that satisfied the string of file1 and store the result in file2 sed 's/old_string/new_string/g' file1 > file2 # replace strings only in lines 200 y 201 sed '200,201 s/old_string/new_string/g' file1 > file2 # replace several strings by new one sed 's/old_string_1\|old_string_2/new_string/g' file1 > file2 # replace all lowercase to uppercase sed 'y/abcdefghijklmnopqrstuvwxyz/ABCDEFGHIJKLMNOPQRSTUVWXYZ/' file1 > file2
Insert strings
As in the previous case, the original file is left unchanged while the second will contain the changes.
# insert a string at the beginning of each line sed 's/^/string_at_the_beginning/' file1 >file2 # insert a string at the end of the file sed -e '$ string_at_the_end' file > file2 # insert a blank line before each line that matches with string sed '/string/{x;p;x;}' file1 > file2 # insert a blank line after each line that matches with string sed '/string/G' file1 > file2 # insert a blank line before and other after each line that matches with string sed '/string/{x;p;x;G;}' file1 > file2 # insert a blank line every 2 lines sed 'n;G;' file1 > file2
Delete lines and strings
If we want to delete characters or entire lines, either because they are empty or commented, we can use the following commands:
sed '2,4 d' file1 > file2 # remove lines 100 and 105 of file1 sed '5,20 !d' file1 > file2 # delete all lines except the 5 and 20 sed '$d' file1 > file2 # delete the last line of file1 sed -i '$d' file1 # delete the last line of file1 in the same file sed '/string/ d' file1 > file2 # remove lines that satisfied a string sed '/^$/d' file1 > file2 # remove blank lines sed '/^$/d; / *#/d' file1 > file2 # remove blank lines and bash comments
Applications for the development of scientific papers, data processing and simulation
24 March 2014Results presentation
The way in which the research results are presented has a significant impact on readers. Also, a good way to represent the information gives a clear and easy ideas to understand. For this, we need a selection of tools that allow the reproduction of documents, photographs, graphics, and other associated items. On the other hand, there are various applications which facilitate the data processing when we need to work with research result, whether mathematical or network.
Linux is a multiuser and multitasking operating system, ie, multiple users can work on the system simultaneously running several tasks at once. It is therefore, very important that the operating system allows the management and control of users.
Unix based systems organize all this by users and groups, where each user must be identified with a user name and password. During login, the password entered by each user, is encrypted and compared to the encrypted passwords that were previously stored in the system.