How to remove the headers from a file using command in Linux?
# sed '1 d' file.txt
Outputs the file on standard output without the first line. In order to save the output to file, we need to use redirect operator which will redirects the output to a file.
# sed '1 d' file.txt > new_file.txt
How will you check the length of a line from a text file?
A ‘sed –n ‘n p’ file.txt‘, where ‘n‘ represents the line number and ‘p‘ print out the pattern space (to the standard
sed –n 'n p' file.txt | wc –c
You are a Team-Leader of a group of staffs working for a company xyz. The company ask you to create a directory ‘dir_xyz’, such that any member of the group can create a file or access a file under it, but no one can delete the file, except the one created it. what will you do?
# mkdir dir_xyz # chmod g+wx dir_xyz # chmod +t dir_xyz
What is the use of cut command in Linux?
# cut -c1-10 txt_tecmint
To extract 2nd, 5th and 7th column of the same text file.
# cut -d;-f2 -f5 -f7 txt_tecmint
sed -n '5,10p' myfile.txt
sed '20,35d' myfile.txt
# sed -n -e '5,7p' -e '10,13p' myfile.txt
To replace every instance of the word version with story in myfile.txt, do:
# sed 's/version/story/g' myfile.txt
Additionally, you may want to consider using gi instead of g in order to ignore character case # sed 's/version/story/gi' myfile.txt
To replace multiple blank spaces with a single space, we will use the output of ip route show and a pipeline:
# ip route show | sed 's/ */ /g'
replacing words only within a line range (30 through 40, for example), you can do:
# sed '30,40 s/version/story/g' myfile.txt
Sometimes configuration files are loaded with comments. While this is certainly useful, it may be helpful to display only the configuration directives sometimes if you want to view them all at a glance.
To remove empty lines or those beginning with # from the Apache configuration file, do:
(^#) indicates the beginning of a line
^$ represents blank lines
In this particular case, the Apache configuration file has lines with #’s not at the beginning of some lines, so *# is used to remove those as well.
# sed '/^#\|^$\| *#/d' httpd.conf
we may be interested in viewing the authorization and authentication activities that took place on July 2, as per the /var/log/secure log in a CentOS 7 server.
sed -n '/^Jul 1/ p' /var/log/secure
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