Category Archives: Linux

Convert comma separated items into new line

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[root@test]# cat input
a,b,c,d
[root@test]# cat input | sed 's/','/\n/g'
a
b
c
d
[root@test]# cat input | awk '$1=$1' RS=, OFS="\n"
a
b
c
d
[root@test]# cat input | tr -s ',' '\n'
a
b
c
d

Enjoy 🙂

Bash scripts to find out missing lines and common lines between two files

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Sometime back I had explained how to find the difference and common lines in two files, Using that giving you 2 simple (very simple) scripts

1. Find out the missing lines between two files

cat diff.sh

#!/bin/bash
if [ $# -eq 0 ];then
        echo "No arguemnts given; Usage : ./diff file2 file1"
        exit 1
fi
echo "Lines exist in $2 and not in $1 are :"
grep -Fxv -f $1 $2

2. Find out the common lines between two files

cat common.sh

#!/bin/bash
if [ $# -eq 0 ];then
        echo "No arguments given; Usage : ./common file1 file2"

        exit 1
fi
echo "Common files in $1 and $2 are :"
awk 'NR==FNR{a[$1]++;next} a[$1] ' $1 $2

Enjoy 🙂

Keyboard copy paste shortcuts in putty commandline

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Everyone know how to copy and paste characters in putty terminal using mouse (in case you don’t know, selecting the characters using mouse automatically copies and right click paste it) but less people know that it is possible with keyboard as well. You can use the below command to paste the characters into putty terminal 

SHIFT + INS

Enjoy 🙂

Compare two files and list common lines

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You can use the awk command to compare two files and show the common ones. Compared to the Linux command “comm”, advantages of using “awk” is it will give output though the files are not sorted.
Syntax :

awk 'NR==FNR{a[$1]++;next} a[$1] ' file1 file2

Eg :

[root@test]# cat A
apple
orange
mango
grape

[root@test]# cat B
mango
banana
grape

[root@test]# awk 'NR==FNR{a[$1]++;next} a[$1] ' A B
mango
grape

Device eth0 does not seem to be present, delaying initialization.

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You might have come across this headline, especially if you working with Oracle Virtual box machines, machines those are cloned from previous setups etc.

device

To resolve the issue, just remove the file /etc/udev/rules.d/70-persistent-net.rules and reboot the machine. This file contains the MAC address details associated with the machine. If you don’t want to reboot the machine, run the below command :

udevadm trigger --subsystem-match=net

This command will trigger the rules again.

Enjoy 🙂

Install Oracle JDK

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Go to the link : http://www.oracle.com/technetwork/java/javase/downloads/

Accept the license agreement and Download the tar.gz file (eg: jdk -8u65-linux-i586.tar.gz)

Extract the file using the command tar -xzvf jdk-8u65-linux-i586.tar.gz

Copy the extracted directory (In my case jdk1.8.0_65) to the required location say /scratch

alternatives –install /usr/bin/java java /scratch/jdk1.8.0_65/bin/java 20000

alternatives –config java

You can see the list of available java versions and select our installed one by typing the number corresponding to that one.

Run a script at boot time in CentOS 7

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By default /etc/rc.local and /etc/rc.d/rc.local are no longer executable in CentOS7 with the new systemd-changes. Follow the below steps to make the script /root/g.sh run at boot time:

1. chmod +x /etc/rc.d/rc.local
2. chmod +x /root/g.sh
2. Mention your script at the bottom of the file /etc/rc.local (/etc/rc.local is a symlink to /etc/rc.d/rc.local)as below :

sh /root/g.sh

Restart and check 🙂