Monthly Archives: March 2017

Linux Tips ( grep the text without hashes and blank lines )

In our second post of linux tips i would like to share a very simple example in which i will use grep tool to remove all the hashes and blank lines from a file.

In our example we will use file1.txt with the following content

linux-11oz:/test # cat file.txt 
#The file with hashes
###
####
##

This is a test file

With lots of spaces


and few lines with


####hashes
###

So lets remove the hashes and blank lines with single grep command

We can use the following trick

linux-11oz:/test # grep . file.txt | grep -v "#"
This is a test file
With lots of spaces
and few lines with

The “.” will remove the blank lines and  “-v” will invert the match of #

Thats how simple it is. If you know a better way of doing it , Please send me an email or comment.

Email: learning@itpings.com

Thanks

Salman A. Francis

 

Linux Tips ( chmod tip )

Hey Guys this is going to be a new series of posts in which i will be sharing some cool linux tips.  You can watch the video of this post on http://www.youtube.com/linuxking

So here is the first tip Chmod:

I hope you guys are already familiar with chmod command if not checkout my Youtube “Linuxking” channel for theses commands.

With Chmod you can change the mode of the files and directories.
e.g
chmod 775 dir  command will change the permission on directory with rwxrwxrw-

Also using -R option with chmod will change the permission on the directory as well the content within the directory with same permissions.

However lets say you want to change the permissions of a directories to executable within a directory without changing permissions of file use the below tip.

Lets say you have a directory “test1” & “test2” inside “test” directory

test directory has also a  file inside it called file1.txt

file1.txt has permission rw——-

directory test1 has permission rwx——

directory test2 has permission rw——-

linux-11oz:/test # ls -ltr
total 0
-rw------- 1 root root 0 Mar 22 17:06 file.txt
drwx------ 1 root root 0 Mar 22 17:07 test2
drwx------ 1 root root 0 Mar 22 17:07 test1

Now if you try to change the permission with a simple ” chmod -R command ” of all the directories to “executable” inside test directory you could also change permission of the file inside test diretory.

Example:

linux-11oz:/ # chmod -R ug+x test/
linux-11oz:/ # cd test/
linux-11oz:/test # ls -ltr
total 0
-rwx--x--- 1 root root 0 Mar 22 17:06 file.txt  (You can see that the file also became executable)
drwx--x--- 1 root root 0 Mar 22 17:07 test2
drwx--x--- 1 root root 0 Mar 22 17:07 test1

Now to avoid such situation we will use X instead of x, lets see the impact of X with chmod command

linux-11oz:/ # chmod -R ug+X test/
linux-11oz:/ # cd test/
linux-11oz:/test # ls -ltr
total 0
-rw------- 1 root root 0 Mar 22 17:06 file.txt (You can see the file's permission has not changed to executable)
drwx--x--- 1 root root 0 Mar 22 17:07 test2
drwx--x--- 1 root root 0 Mar 22 17:07 test1
linux-11oz:/test #

I hope you have Enjoyed this tip, keep visiting our site for more information.