How to check system information on CentOS Linux from CLI

To check the system information of CentOS Linux from command line interface, the following commands will come in handy.

cat /proc/cpuinfo

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 6
model           : 45
model name      : Intel(R) Xeon(R) CPU E5-4620 0 @ 2.20GHz
stepping        : 2
microcode       : 0x710
cpu MHz         : 2200.000
cache size      : 16384 KB
physical id     : 2
siblings        : 1
core id         : 0
cpu cores       : 1
apicid          : 2
initial apicid  : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts mmx fxsr sse sse2 ss syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts nopl xtopology tsc_reliable nonstop_tsc aperfmperf pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 popcnt aes xsave avx hypervisor lahf_lm ida arat pln pts dtherm
bogomips        : 4400.00
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management:

To check the memory details use the following :

vmstat -s

 3883788 K total memory

      3758516 K used memory

      2232252 K active memory

      1263620 K inactive memory

       125272 K free memory

            0 K buffer memory

       259872 K swap cache

      8191996 K total swap

      3114568 K used swap

      5077428 K free swap

    411521845 non-nice user cpu ticks

        23449 nice user cpu ticks

    116773236 system cpu ticks

   5900085167 idle cpu ticks

      1174004 IO-wait cpu ticks

         1058 IRQ cpu ticks

      7376135 softirq cpu ticks

            0 stolen cpu ticks

    234643114 pages paged in

    380977726 pages paged out

      3875967 pages swapped in

      4295358 pages swapped out

    948364036 interrupts

   1524453860 CPU context switches

   1479654445 boot time

    130969946 forks

You could also use an alternative command :

cat /proc/meminfo

MemTotal:        3883788 kB
MemFree:          119860 kB
MemAvailable:      89684 kB
Buffers:               0 kB
Cached:            64528 kB
SwapCached:       455596 kB
Active:          2526176 kB
Inactive:         993336 kB
Active(anon):    2503132 kB
Inactive(anon):   954552 kB
Active(file):      23044 kB
Inactive(file):    38784 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       8191996 kB
SwapFree:        4795948 kB
Dirty:                96 kB
Writeback:             0 kB

Listing repositories in CentOS Linux

In CentOS and Red Hat flavors of Linux, if we want to list all the configured repositories, we need to use the following command.

yum repolist

This will list information with columns like repo id, repo name, status.

Use the verbose mode with the -v switch for more detailed information.

yum -v repolist

For listing only enabled and/or disabled repositories, use the following syntax

yum repolist enabled

OR

yum repolist disabled

For listing all of the repositories (i.e enabled and disabled), use :

yum repolist all

Now, from the list of of all configured repositories, if we want to disable/enable a specific repository, use the following :

yum-config-manager --disable test-repo-name.repo

OR

yum-config-manager --enable test-repo-name.repo

Hope it helps guys. Ciao!

Automate regular backups of SonarQube's DB using bash script

Guys, this post will be useful if you are using SonarQube for code analysis and quality control. In today's post we will look into how to automate taking regular backups of SonarQube's back-end database.

For illustration, we will use MySql DB to store SonarQube's metadata which includes analysis parameters like code smells, bugs, code coverage, unit test coverage etc. In this case we host Sonar on a linux machine, so we write a bash script to take regular backups of the MySql DB. Take a look at a simple sample script below :

#!/bin/bash
# script for taking database dump of sonar

user="root";
hostname="localhost";
db_name="sonar";
dateformat=`date +%d-%m-%y`;

mysqldump --defaults-extra-file="/usr/local/cron_scripts/.my.cnf" -u $user -h $hostname sonar | gzip > /usr/local/mysql_dumps/sonar_dump_$dateformat.sql.gz

chmod 755 /usr/local/mysql_dumps/sonar_dump_$dateformat.sql.gz

As you see, we have used mysqldump to take dump of the database, zip it, append it with the current date and store it at the said location.

Taking dumps of Sonar can be extremely useful for the purpose of importing and exporting of a Sonar instance from one machine to another without losing the analysis history.

How to open specific port in firewall in CentOS Linux

Guys, if your organization is behind a firewall, the networking team usually takes care that most unused ports are blocked, unless absolutely necessary. In some cases, you may want to add an exception to the firewall rules though, to open up a specific port to allow incoming and outgoing network traffic.

In today's example, we may want to open up a port 8080 to allow TCP connections for instance. Note that these commands are specifically for the CentOS flavor of Linux. Other flavors of Linux may have different command syntax. Please check accordingly.

Firstly view the existing firewall rules using the following command

firewall-cmd --list-all

Output (Old rules):

public (default, active)
  interfaces: en0
  sources:
  services: dhcpv6-client ssh
  ports: 9005/tcp
  masquerade: no
  forward-ports:
  icmp-blocks:
  rich rules:

As you see from the existing rules, it seems that port 9005 is open. Now let us add the port 8080 to the firewall rules using the below command. If the command is executed fine, it will display "success". Make sure to reload firewall configuration to bring the new rules into effect.

firewall-cmd --zone=public --add-port=8080/tcp --permanent
success

firewall-cmd --reload
success

In order to view the double check the firewall rules, again use the --list-all command.

firewall-cmd --list-all

Output ( Updated rules):

public (default, active)
  interfaces: en0
  sources:
  services: dhcpv6-client ssh
  ports: 8080/tcp 9005/tcp
  masquerade: no
  forward-ports:
  icmp-blocks:
  rich rules:

As you see the port 8080 has been added to the list i.e it has been opened up.

Extract pom.xml version number using Shell script - Scenario 1

Guys, in todays post we'll look into an example where we want to extract version number from pom.xml of a Maven based project. In other words, all we have to do is extract text between 2 strings from a file. Quite obviously we would use sed for that. But let's look into a scenario where you have to pipe sed to other unix commands.

FYI this will work universally on Linux/Unix/Mac OS X flavors.

Let's say I have a pom.xml file of a Maven based project and I want to display only the version number from it. As you may be aware, we define the version number within the <version> </version> tags.

For e.g. my pom.xml looks something like this :

Here we want to extract only the version number from the file. i.e in this case I only want to display 1.0-SNAPSHOT.

Did you notice that in our file we have two lines of the <version></version> tags. One for our main project version and the other is for the dependency version. Now if we use sed to extract text between the "version" words, it will give output like this below.

sed -n '/version/,/version/p' pom.xml

  <version>1.0-SNAPSHOT</version>

  <packaging>jar</packaging>

  <name>testapp</name>

  <url>http://maven.apache.org</url>

  <properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

  </properties>

  <dependencies>

    <dependency>

      <groupId>junit</groupId>

      <artifactId>junit</artifactId>

      <version>3.8.1</version>

So let's display only the topmost line with head -1. That should help narrow down our output.

sed -n '/version/,/version/p' pom.xml | head -1

  <version>1.0-SNAPSHOT</version>

Now all we need is to extract the version number. Let's cut the output characters as follows :

sed -n '/version/,/version/p' pom.xml | head -1 | cut -c 12-23

1.0-SNAPSHOT

Cheers guys! That's what we wanted right? Now we could perhaps develop a script around this. Maybe have a variable which stores this version number. Perhaps we could use this variable for some conditional checks. Something like this :

#!/bin/bash

# Program to extract version number from the pom.xml

i=`sed -n '/version/,/version/p' /Users/ironcladzone/workspace/MavenTest/testapp/pom.xml | head -1 | cut -c 12-23`

echo $i

if [ $i = "1.0-SNAPSHOT" ]; then

echo "Version 1.0 Development copy. Team A is working on it."

else

echo "That's not a Version 1.0 Dev copy"

fi

Output :

./ExtractVersionFromPom.sh

1.0-SNAPSHOT

Version 1.0 Development copy. Team A is working on it.

The possibilities are limitless! Until next time, ciao!

Print a triangle using * in a Bash script

Hello coders! Hows it going? Today we'll see a basic simple shell script to print a triangle using asterisk * only. Here's the code to do that :

#!/bin/bash

# Simple program to print a triangle using * of height 10

star="*"

for i in {1..10}

do

echo "$star";

star="$star *"

done

You see basically, all we are doing is append a * to itself recursively. Here we are using a basic for-loop to print a triangle of height 10. You can change the height as per your requirement, as needed.

Output :

*

* *

* * *

* * * *

* * * * *

* * * * * *

* * * * * * *

* * * * * * * *

* * * * * * * * *

* * * * * * * * * *

Cheers!

Identify exact port number used by a process or app on Mac OSX

Guys, if you ever wanted to find out the exact specific port number used by a process/application on Unix/Mac OSX/Linux, type the following in Terminal :

top | awk '{print $2, $7}'

The output would be something like :

COMMAND #PORTS

awk 12

top 22+

top 19

This will show only the specific Command and Port columns from the top command and will skip other details like Process ID, % CPU utilisation , Memory usage etc.

Alternatively if you wanted to just find the port number used by a specific application, say for e.g. TextEdit, you could use the following command :

top | awk '{print $2, $7}' | grep TextEdit

TextEdit 140+

TextEdit 140

TextEdit 140

Cheers guys!

Read file line by line and count no. of lines using Shell script

Guys, in today's post we'll see how to parse a file line by line and count the number of lines in it.

We will simply use redirection to read the file. Note that we will pass the filename as a runtime parameter to the script.

Alright here we go. Suppose I have a file TextFile1.txt with the following contents. I want to print the total number of lines in it.

ABCD

DEFG

GHI

JKL

MNO

PQR

STU

VWXYZ

Now, here's the script part.

#!/bin/bash

#Sript to count number of lines in a file

File=$1

count=0

while read LINE

do

let count++

echo "$count $LINE"

done < $File

echo -e "Total $count Lines read\n"

Here's the output :

1 ABCD

2 DEFG

3 GHI

4 JKL

5 MNO

6 PQR

7 STU

8 VWXYZ

Total 8 Lines read

Cheers it has correctly displayed the count of lines in the file. In case of any questions/doubts, kindly leave your comments.

Search for string in a file and print the line : Unix basics

Guys, lets look into a very basic topic today. Today we'll see how to search for a string in a file and print the line in Unix/Linux/Mac OS X

Suppose I have a file SedText.rtf with the following text :

1.Here is a cute little tutorial for

2.trying out different things using

3.the Stream Editor or Sed in Unix.

4.The author of this tutorial is

5.none other than IroncladWriter

6.himself. The tutorial aims to

7.teach folks and educate how

8.they could unlock the power

9.of Unix to the fullest. Am posting

10.this on the blog IronCladZone

11.The best blog on the whole of

12.internet, where you can learn

13.technical stuff as well enjoy 

14.entertaining tidbits like movies,

15.music, television, fashion, food,

16.shopping, travel, trends etc.

17.Just sit back, relax and

18.ENJOY THE RIDE :)

Now I want to search this file for the keyword "Unix" and print all the lines. All we have to do is use the grep statement. Check this out :

grep Unix SedText.rtf

3.the Stream Editor or Sed in Unix.\

9.of Unix to the fullest. Am posting\

Character Combinations using Shell Script

In today's post we'll look into a very simple entry level bash script in which we form all possible alphanumeric combinations using just 2 characters and save it in a file. You could tweak the program to suit your needs - e.g. all combinations of 6 or 7 or 8 characters or maybe include special characters as well. The file in which all these combinations are stored would be more like a dictionary.

#!/bin/bash

# Program to print all possible 2-character combinations

echo {a..z}{0..9} > /Users/ironcladzone/Documents/xyz.txt

echo {0..9}{a..z} >> /Users/ironcladzone/Documents/xyz.txt

Here's the output of xyz.txt :

a0 a1 a2 a3 a4 a5 a6 a7 a8 a9 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 c0 c1 c2 c3 c4 c5 c6 c7 c8 c9 d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 e0 e1 e2 e3 e4 e5 e6 e7 e8 e9 f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 g0 g1 g2 g3 g4 g5 g6 g7 g8 g9 h0 h1 h2 h3 h4 h5 h6 h7 h8 h9 i0 i1 i2 i3 i4 i5 i6 i7 i8 i9 j0 j1 j2 j3 j4 j5 j6 j7 j8 j9 k0 k1 k2 k3 k4 k5 k6 k7 k8 k9 l0 l1 l2 l3 l4 l5 l6 l7 l8 l9 m0 m1 m2 m3 m4 m5 m6 m7 m8 m9 n0 n1 n2 n3 n4 n5 n6 n7 n8 n9 o0 o1 o2 o3 o4 o5 o6 o7 o8 o9 p0 p1 p2 p3 p4 p5 p6 p7 p8 p9 q0 q1 q2 q3 q4 q5 q6 q7 q8 q9 r0 r1 r2 r3 r4 r5 r6 r7 r8 r9 s0 s1 s2 s3 s4 s5 s6 s7 s8 s9 t0 t1 t2 t3 t4 t5 t6 t7 t8 t9 u0 u1 u2 u3 u4 u5 u6 u7 u8 u9 v0 v1 v2 v3 v4 v5 v6 v7 v8 v9 w0 w1 w2 w3 w4 w5 w6 w7 w8 w9 x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 y0 y1 y2 y3 y4 y5 y6 y7 y8 y9 z0 z1 z2 z3 z4 z5 z6 z7 z8 z9
0a 0b 0c 0d 0e 0f 0g 0h 0i 0j 0k 0l 0m 0n 0o 0p 0q 0r 0s 0t 0u 0v 0w 0x 0y 0z 1a 1b 1c 1d 1e 1f 1g 1h 1i 1j 1k 1l 1m 1n 1o 1p 1q 1r 1s 1t 1u 1v 1w 1x 1y 1z 2a 2b 2c 2d 2e 2f 2g 2h 2i 2j 2k 2l 2m 2n 2o 2p 2q 2r 2s 2t 2u 2v 2w 2x 2y 2z 3a 3b 3c 3d 3e 3f 3g 3h 3i 3j 3k 3l 3m 3n 3o 3p 3q 3r 3s 3t 3u 3v 3w 3x 3y 3z 4a 4b 4c 4d 4e 4f 4g 4h 4i 4j 4k 4l 4m 4n 4o 4p 4q 4r 4s 4t 4u 4v 4w 4x 4y 4z 5a 5b 5c 5d 5e 5f 5g 5h 5i 5j 5k 5l 5m 5n 5o 5p 5q 5r 5s 5t 5u 5v 5w 5x 5y 5z 6a 6b 6c 6d 6e 6f 6g 6h 6i 6j 6k 6l 6m 6n 6o 6p 6q 6r 6s 6t 6u 6v 6w 6x 6y 6z 7a 7b 7c 7d 7e 7f 7g 7h 7i 7j 7k 7l 7m 7n 7o 7p 7q 7r 7s 7t 7u 7v 7w 7x 7y 7z 8a 8b 8c 8d 8e 8f 8g 8h 8i 8j 8k 8l 8m 8n 8o 8p 8q 8r 8s 8t 8u 8v 8w 8x 8y 8z 9a 9b 9c 9d 9e 9f 9g 9h 9i 9j 9k 9l 9m 9n 9o 9p 9q 9r 9s 9t 9u 9v 9w 9x 9y 9z

Area & Circumference of a circle - Shell script for Mac OS X

Guys in todays post let us look into a simple basic Mathematics problem. Let us automate the calculation of area and circumference of a circle, using a simple bash script. It's an easy script useful for learning some basic shell scripting.

Note : Value of pi used is a constant value rounded off to 3.142

#!/bin/bash

#program to calculate area and circumference of a circle

echo "=========================================="

echo "Area & Circumference of Circle Calculator"

echo "=========================================="

pi=3.142

echo "Please enter the radius of the circle : "

read radius

circumference=`expr "2*$pi*$radius"|bc`

echo "Circumference of circle : $circumference"

area=`expr "$pi*$radius*$radius"|bc`

echo "Area of circle : $area"

Output :

./AreaOfCircle.sh

==========================================

Area & Circumference of Circle Calculator

==========================================

Please enter the radius of the circle : 

5

Circumference of circle : 31.420

Area of circle : 78.550

Also do check out my previous post on Simple Interest Tool for additional scripting reference.

Script to check if a server / machine is up and running

Guys you might often come across some situations where you want to check if a server or machine is physically up and running. Quite obviously you would use the ping command to do so.

But in today's post let us write a simple bash script to automate this.

#!/bin/bash

#program to check if a server/machine is up and running

ipaddr=192.168.1.34

ping -c 4 $ipaddr >> /dev/null

if [[ $? -ne 0 ]]

then

echo "FAIL: Server seems to be down and not responding" 

else

echo "SUCCESS : Server is up and running"

fi

Note : $? is a special Unix variable to check if the previous command was executed successfully or not. It returns a numerical value - either 0 or 1. If the command was executed successfully, it returns 0, else if not, it returns 1.

In above script, simply replace the variable 'ipaddr' value to your server's ip address and check.

Also note that by redirecting the output of the ping command to /dev/null, we are suppressing and silencing the output i.e the ping o/p will not be shown on terminal. If you want to see the exact output of ping, remove the ">> /dev/null" part.

Output :

./PingServer.sh

SUCCESS : Server is up and running

Cheers!

How to identify available shells on Mac OS X

Guys you may be aware that you can find your current shell in Mac OSX or any Unix machine by typing the following in Terminal.

echo $SHELL

/bin/bash

But to identify the available shells on Mac OS X type the following :

cat /etc/shells

# List of acceptable shells for chpass(1).

# Ftpd will not allow users to connect who are not using

# one of these shells.

/bin/bash

/bin/csh

/bin/ksh

/bin/sh

/bin/tcsh

/bin/zsh

Also, if you ant to change your default shell, type this :

chsh

Changing shell for ironcladzone.

Password for ironcladzone: 

Hope it helps. Cheers!

Modify a part of file path using Sed in Mac OS X - Tricky Scenario

Lets look into a fairly simple task with a slight twist today - update/modify a part of the file paths mentioned within a file using Sed from command line in Unix/Mac OS X. Mark this as a tricky interview question.

Let's consider a simple example. For instance we have a text file named Filepaths.txt which has the following file path details :

/Users/ironcladzone/Downloads/file1.txt

/Users/ironcladzone/Downloads/image.jpg

/Users/ironcladzone/Downloads/presentation.ppt

/Users/ironcladzone/Downloads/Spreadsheet.xls

/Users/ironcladzone/Downloads/Audio.mp3

/Users/ironcladzone/Downloads/Movie.avi

/Users/Shared/Downloads/Test1

/Users/Shared/Downloads/ABC

/Users/ironcladzone/Downloads/MovieClip.mov

Here we want to replace only a part of the file path i.e replace all instances of the word"Downloads" with "Documents". Sure you can instantly do it in some text editor using "Replace All". But the catch is I want to replace the word Downloads with Documents if and only if it exists in the /Users/ironcladzone/Downloads/ path. I want to skip all other file paths. In this case I want the path /Users/Shared/Downloads/Test1 & /Users/Shared/Downloads/ABC to remain intact and unchanged.

So let's see how to do it from command line using a Sed regex.

Open up terminal and type this :

sed 's/\/Users\/ironcladzone\/Downloads/\/Users\/ironcladzone\/Documents/g' FilePaths.txt

So here's the output as expected. Cheers!

/Users/ironcladzone/Documents/file1.txt

/Users/ironcladzone/Documents/image.jpg

/Users/ironcladzone/Documents/presentation.ppt

/Users/ironcladzone/Documents/Spreadsheet.xls

/Users/ironcladzone/Documents/Audio.mp3

/Users/ironcladzone/Documents/Movie.avi

/Users/Shared/Downloads/Test1

/Users/Shared/Downloads/ABC

/Users/ironcladzone/Documents/MovieClip.mov

Double digit Arguments Passed to Shell script - Tricky Scenario

Guys, you know that $# is a special variable that gives the arguments passed to the shell script.

$1 will give the 1st argument passed, $4 will give the 4th argument passed to the script.

Let's consider a tricky scenario. 
Note : This is a tricky interview question.

Let's say you want to pass 12 arguments to the script.

Did you notice that after 9th argument, all arguments passed would be of 2 digits... I mean the 10th, 11th and 12th argument.

So let's say to get the 12th argument, you may tend to use $12. But hey look again! Thats not right! The script doesn't understand that. Check out a practical example to know what I mean.

Let's take a simple bash script and compare the output of Wrong and Correct versions.

[WRONG VERSION]

#!/bin/bash

# Call this script with 12 parameters

echo "1st parameter is $1";

echo "2nd parameter is $2";

echo "3rd paramter is $3";

echo "4th parameter is $4";

echo "5th paramter is $5";

echo "6th parameter is $6";

echo "7th parameter is $7";

echo "8th paramter is $8";

echo "9th parameter is $9";

echo "10th parameter is $10";

echo "11th parameter is $11";

echo "12th paramter is $12";

Now lets say you execute the script with 12 arguments. Watch the output :

./Parameters_Pass.sh 5 10 15 20 25 30 32 35 42 45 50 65

1st parameter is 5

2nd parameter is 10

3rd paramter is 15

4th parameter is 20

5th paramter is 25

6th parameter is 30

7th parameter is 32

8th paramter is 35

9th parameter is 42

10th parameter is 50

11th parameter is 51

12th paramter is 52

See how the 10th 11th and 12t argument that we passed got screwed up. Instead of 45, 50, 65 what we see is 50, 51 and 52. Thats's so wrong, right?

Now here's the correct version of the script.

[CORRECT VERSION]

#!/bin/bash

# Call this script with 12 parameters

echo "1st parameter is $1";

echo "2nd parameter is $2";

echo "3rd paramter is $3";

echo "4th parameter is $4";

echo "5th paramter is $5";

echo "6th parameter is $6";

echo "7th parameter is $7";

echo "8th paramter is $8";

echo "9th parameter is $9";

echo "10th parameter is ${10}";

echo "11th parameter is ${11}";

echo "12th paramter is ${12}";

Observe the brace brackets used for 10th, 11th and 12th argument. Now if you execute the script with 12 arguments again, we'll get the correct output as expected.

./Parameters_Pass.sh 5 10 15 20 25 30 32 35 42 45 50 65

1st parameter is 5

2nd parameter is 10

3rd paramter is 15

4th parameter is 20

5th paramter is 25

6th parameter is 30

7th parameter is 32

8th paramter is 35

9th parameter is 42

10th parameter is 45

11th parameter is 50

12th paramter is 65

List only hidden files in Unix / Mac OS X

Folks you may be aware that ls -a will list all hidden files and visible files as well.

But to list only the hidden files, type the following in Terminal :

ls -ld .?*

This is one of the tricky interview questions, so make a note of this.

How to change Bash History Size on Mac OS X

Guys, I hope you must be aware, that the commands that you type in terminal get saved in the history. On Mac OS X, the default size of commands history is 500 i.e it saves the most recent 500 commands that you typed in terminal in a special file named "bash_history".

Open Terminal and check for yourself.

vi ~/.bash_history

Hit escape and type this to see the history limit
:set number

Now to change this default limit of 500 to something else, lets do the following in Terminal.

sudo vi ~/.bash_profile

Enter your password.

Add this line to the file :

#history

HISTFILESIZE=1000

That's it. It means from now on, it will save upto 1000 latest commands that you typed in history. Ciao!

Remove all Whitespaces from a file in Mac OS X

Lets look into a simple task today - remove all whitespaces from a file in Unix / Mac OS X from the command line.

To do so, let's consider a small example.

Let's have simple text file named Space_File.txt withe the below content. You see it's a regular text file with words separated with spaces.

1.Here is a cute little tutorial for

2.trying out different things using

3.the Stream Editor or Sed in Unix.

4.The author of this tutorial is

5.none other than IroncladWriter

6.himself. The tutorial aims to

7.teach folks and educate how

8.they could unlock the power

9.of Unix to the fullest. Am posting

10.this on the blog IronCladZone

11.The best blog on the whole of

12.internet, where you can learn

13.technical stuff as well enjoy 

14.entertaining tidbits like movies,

15.music, television, fashion, food,

16.shopping, travel, trends etc.

17.Just sit back, relax and

18.ENJOY THE RIDE :)

Now, we want to remove all the whitespace between the words. So let's use the following command.

tr -d ' \d' <Space_File.txt >NoSpace_File.txt

In this we pass the Space_Text.txt as input and redirect the output to a new file - NoSpace_File.txt. Note the space before \d. Do not miss this space. I repeat, DO NOT miss this space. It has to be ' \d' and not '\d'. Got it? All rite so the resultant output is as expected with no spaces:

1.Hereisacutelittletutorialfor

2.tryingoutifferentthingsusing

3.theStreamEitororSeinUnix.

4.Theauthorofthistutorialis

5.noneotherthanIronclaWriter

6.himself.Thetutorialaimsto

7.teachfolksaneucatehow

8.theycoulunlockthepower

9.ofUnixtothefullest.Amposting

10.thisontheblogIronClaZone

11.Thebestblogonthewholeof

12.internet,whereyoucanlearn

13.technicalstuffaswellenjoy

14.entertainingtibitslikemovies,

15.music,television,fashion,foo,

16.shopping,travel,trensetc.

17.Justsitback,relaxan

18.ENJOYTHERIDE:)

Show line numbers in vi editor on Mac OS X

Guys in vi editor in order to show the line numbers, do the following :

Open vi editor to create or open a script
Click escape (esc) key and type colon.
Now enter set number and Enter

Check out the screenshot for reference :

Cheers!

How to debug shell / bash scripts

While executing the bash scripts, if you want to debug them i.e you want to trace the exact sequence of steps that get executed, continue reading this post below.

Just below the shebang line on top of every script, type this :

set -x

That's it.

Let's take the example of killing a process / application using shell script that we saw in our previous post. Assuming you have opened the application - TextWrangler and want to close it using a bash script.

#!/bin/bash

set -x

kill -9 `ps -ef | grep TextWrangler | awk '{print $2}'`;

Now here's the output for the same :

++ ps -ef

++ grep TextWrangler

++ awk '{print $2}'

+ kill -9 24677 24678 24682

Note that 24677 24678 and 24682 are all PID's of all processes associated with TextWrangler. In this way you can track the flow of the script in which the tasks get executed. Debugging can be of great help if you have a complex flow of program and need to identify the sequence of steps in which they are executed.