0x2B|~0x2B – Page 15 – My broken wings still strong enough to cross the ocean with.

Learning Bash Scripts (3)

October 4, 2011 by gonwan·0 Comments

This post covers the loop usage of bash shell. NOTE: read inline comments carefully 🙂

1. for loop

#!/bin/bash

# loop list, last value remains
for test in Alabama Alaska Arizona Arkansas California Colorado
do
    echo The next state is $test
done
echo "The last state we visited was $test"
test=Connecticut
echo "Wait, now we're visiting $test"

# using escape or quote
for test in I don\'t know if "this'll" work
do
    echo "word: $test"
done

# loop variable & files
states="Alabama Alaska Arizona Arkansas Colorado Connecticut Delaware Florida Georgia"
statesfile=states.txt
for state in $states; do
    echo $state >> $statesfile
done
for state in `cat $statesfile`; do
    echo "Visit beautiful $state"
done
rm $statesfile

# loop directory
for file in ~/.b*; do
    if [ -d "$file" ]; then
        echo "$file is a directory"
    elif [ -f "$file" ]; then
        echo "$file is a file"
    else
        echo "$file doesn't exist"
    fi
done

# c-style syntax
for (( i = 1; i <= 10; i++ )); do
    echo "The next number is $i"
done

# IFS (internal field separator) to separator string
IFSHOLD=$IFS
IFS=$'\n'
for entry in `cat /etc/passwd`; do
    echo "Values in $entry:"
    IFS=:
    for value in $entry; do
        echo "  $value"
    done
done
IFS=$IFSHOLD

#!/bin/bash

# loop list, last value remains

for test in Alabama Alaska Arizona Arkansas California Colorado

echo The next state is $test

done

echo "The last state we visited was $test"

test=Connecticut

echo "Wait, now we're visiting $test"

# using escape or quote

for test in I don\'t know if "this'll" work

echo "word: $test"

done

# loop variable & files

states="Alabama Alaska Arizona Arkansas Colorado Connecticut Delaware Florida Georgia"

statesfile=states.txt

for state in $states; do

echo $state >> $statesfile

done

for state in `cat $statesfile`; do

echo "Visit beautiful $state"

done

rm $statesfile

# loop directory

for file in ~/.b*; do

if [ -d "$file" ]; then

echo "$file is a directory"

elif [ -f "$file" ]; then

echo "$file is a file"

else

echo "$file doesn't exist"

done

# c-style syntax

for (( i = 1; i <= 10; i++ )); do

echo "The next number is $i"

done

# IFS (internal field separator) to separator string

IFSHOLD=$IFS

IFS=$'\n'

for entry in `cat /etc/passwd`; do

echo "Values in $entry:"

IFS=:

for value in $entry; do

echo " $value"

done

IFS=$IFSHOLD

2. while loop

#!/bin/bash

var1=10
while [ $var1 -gt 0 ]; do
    echo $var1
    var1=$[ $var1 - 1 ]
done

#!/bin/bash

var1=10

while [ $var1 -gt 0 ]; do

echo $var1

var1=$[ $var1 - 1 ]

done

3. until loop

#!/bin/bash

var1=100
until [ $var1 -eq 0 ]; do
    echo $var1
    var1=$[ $var1 - 25 ]
done

#!/bin/bash

var1=100

until [ $var1 -eq 0 ]; do

echo $var1

var1=$[ $var1 - 25 ]

done

4. break & continue

#!/bin/bash

# break
for (( a = 1; a < 4; a++ )); do
    echo "Outer loop: $a"
    for (( b = 1; b < 100; b++ )); do
        if [ $b -eq 5 ]; then
            break
        fi
        echo "Inner loop: $b"
    done
done

# break outer loop
for (( a = 1; a < 4; a++ )); do
    echo "Outer loop: $a"
    for (( b = 1; b < 100; b++ )); do
        if [ $b -eq 5 ]; then
            break 2
        fi
        echo "Inner loop: $b"
    done
done

# continue outer loop
for (( a = 1; a <= 5; a++ )); do
    echo "Iteration $a:"
    for (( b = 1; b < 3; b++ )); do
        if [ $a -gt 2 ] && [ $a -lt 4 ]; then
            continue 2
        fi
        var3=$[ $a * $b ]
        echo "  The result of $a * $b is $var3"
    done
done

#!/bin/bash

# break

for (( a = 1; a < 4; a++ )); do

echo "Outer loop: $a"

for (( b = 1; b < 100; b++ )); do

if [ $b -eq 5 ]; then

break

echo "Inner loop: $b"

done

# break outer loop

for (( a = 1; a < 4; a++ )); do

echo "Outer loop: $a"

for (( b = 1; b < 100; b++ )); do

if [ $b -eq 5 ]; then

break 2

echo "Inner loop: $b"

done

# continue outer loop

for (( a = 1; a <= 5; a++ )); do

echo "Iteration $a:"

for (( b = 1; b < 3; b++ )); do

if [ $a -gt 2 ] && [ $a -lt 4 ]; then

continue 2

var3=$[ $a * $b ]

echo " The result of $a * $b is $var3"

done

There may be times when you’re in an inner loop but need to stop the outer loop. The break command includes a single command line parameter value: break n where n indicates the level of the loop to break out of. By default, n is 1, indicating to break out of the current loop. If you set n to a value of 2, the break command will stop the next level of the outer loop.

5. redirect & pipe

Finally, you can either pipe or redirect the output of a loop within your shell script.

#!/bin/bash

testfile=testloop.txt
for (( a = 1; a < 10; a++ )); do
    echo "The number is $a"
done > $testfile
echo "The command is finished."
cat $testfile
rm $testfile

#!/bin/bash

testfile=testloop.txt

for (( a = 1; a < 10; a++ )); do

echo "The number is $a"

done > $testfile

echo "The command is finished."

cat $testfile

rm $testfile

Learning Bash Scripts (2)

October 4, 2011 by gonwan·0 Comments

1. Comments

When creating a shell script file, you must specify the shell you are using in the first line of the file. The format for this is:

#!/bin/bash
# This script displays the date and who's logged on
date
who

#!/bin/bash

# This script displays the date and who's logged on

date

who

In a normal shell script line, the pound sign(#) is used as a comment line. A comment line in a shell script isn’t processed by the shell. However, the first line of a shell script file is a special case, and the pound sign followed by the exclamation point tells the hell what shell to run the script under (yes, you can be using a bash shell and run your script using another shell).

2. Display

The echo command can display a simple text string if you add the string following the command.

#!/bin/bash
# basic usage
echo This is a test.
echo "Let's see if this'll work"
# environment variables
echo "User info for user: $USER"
echo UID: $UID
echo HOME: $HOME
echo "The cost of the item is \$15"
# user variables
days=10
guest="Katie"
echo "$guest checked in $days days ago"
days=5
guest="Jessica"
echo "$guest checked in $days days ago"
# backtip
testing=`date`
echo "The date and time are: " $testing

#!/bin/bash

# basic usage

echo This is a test.

echo "Let's see if this'll work"

# environment variables

echo "User info for user: $USER"

echo UID: $UID

echo HOME: $HOME

echo "The cost of the item is \$15"

# user variables

days=10

guest="Katie"

echo "$guest checked in $days days ago"

days=5

guest="Jessica"

echo "$guest checked in $days days ago"

# backtip

testing=`date`

echo "The date and time are: " $testing

The echo command uses either double or single quotes to delineate text strings. If you use them within your string, you need to use one type of quote within the text and the other type to delineate the string.

Notice that the environment variables in the echo commands are replaced by their current values when the script is run. Also notice that we were able to place the $USER system variable within the double quotation marks in the first string, and the shell script was still able to figure out what we meant.

You may also see variables referenced using the format ${variable}. The extra braces around the variable name are often used to help identify the variable name from the dollar sign.

User variables can be any text string of up to 20 letters, digits, or an underscore character. User variables are case sensitive, so the variable Var1 is different from the variable var1. This little rule often gets novice script programmers in trouble.

Values are assigned to user variables using an equal sign. No spaces can appear between the variable, the equal sign, and the value (another trouble spot for novices). Here are a few examples of assigning values to user variables.

The shell script automatically determines the data type used for the variable value. Variables defined within the shell script maintain their values throughout the life of the shell script but are deleted when the shell script completes.

Just like system variables, user variables can be referenced using the dollar sign. It’s important to remember that when referencing a variable value you use the dollar sign, but when referencing the variable to assign a value to it, you do not use the dollar sign.

The backtick allows you to assign the output of a shell command to a variable.

3. Redirect I/O

>: output redirect
>>: output redirect append data
<: input redirect
<<: inline input redirect

# wc << EOF
> test string 1
> test string 2
> test string 3
> EOF
    3    9    42
#

# wc << EOF

> test string 1

> test string 2

> test string 3

> EOF

3 9 42

The inline input redirection symbol is the double less-than symbol (<<). Besides this symbol, you must specify a text marker that delineates the beginning and end of the data used for input. You can use any string value for the text marker, but it must be the same at the beginning of the data and the end of the data.

4. Math Expression

#!/bin/bash
var1=10
var2=3
var3=`expr $var1 \* $var2`
var4=$[$var1 * $var2]
var5=`expr $var1 / $var2`
var6=$[$var1 / $var2]
var7=`echo "scale=3; $var1 / $var2" | bc`
echo The result is $var3
echo The result is $var4
echo The result is $var5
echo The result is $var6
echo The result is $var7

#!/bin/bash

var1=10

var2=3

var3=`expr $var1 \* $var2`

var4=$[$var1 * $var2]

var5=`expr $var1 / $var2`

var6=$[$var1 / $var2]

var7=`echo "scale=3; $var1 / $var2" | bc`

echo The result is $var3

echo The result is $var4

echo The result is $var5

echo The result is $var6

echo The result is $var7

The expr command allowed the processing of equations from the command line. Note the spaces around operator is necessary. Escape character(backslash) is used to identify any characters that may be misinterpreted by the shell before being passed to the expr command.

Bash also provides a much easier way of performing mathematical equations. In bash, when assigning a mathematical value to a variable, you can enclose the mathematical equation using a dollar sign and square brackets ($[ operation ]).

The bash shell mathematical operators support only integer arithmetic. The most popular solution uses the built-in bash calculator, called bc.

5. Structured Commands

5.1 if/else

The bash shell if statement runs the command defined on the if line. If the exit status of the command is zero (the command completed successfully), the commands listed under the then section are executed. If the exit status of the command is anything else, the then commands aren’t executed, and the bash shell moves on to the next command in the script.

#!/bin/bash
user=gonwan
user2=test2
user3=test3
# if-then
if grep $user /etc/passwd; then
    echo "The bash files for user $user are:"
    ls -a /home/$user/.b*
fi
# if-then-else
if grep $user2 /etc/passwd; then
    echo "The bash files for user $user2 are:"
    ls -a /home/$user2/.b*
else
    echo "The user name $user2 does not exist on this system"
fi
#if-then-elif-then-else
if grep $user3 /etc/passwd; then
    echo "The bash files for user $user3 are:"
    ls -a /home/$user3/.b*
elif grep $user2 /etc/passwd; then
    echo "The bash files for user $user2 are:"
    ls -a /home/$user2/.b*
else
    echo "The user name $user2 and $user3 does not exist on this system"
fi

#!/bin/bash

user=gonwan

user2=test2

user3=test3

# if-then

if grep $user /etc/passwd; then

echo "The bash files for user $user are:"

ls -a /home/$user/.b*

# if-then-else

if grep $user2 /etc/passwd; then

echo "The bash files for user $user2 are:"

ls -a /home/$user2/.b*

else

echo "The user name $user2 does not exist on this system"

#if-then-elif-then-else

if grep $user3 /etc/passwd; then

echo "The bash files for user $user3 are:"

ls -a /home/$user3/.b*

elif grep $user2 /etc/passwd; then

echo "The bash files for user $user2 are:"

ls -a /home/$user2/.b*

else

echo "The user name $user2 and $user3 does not exist on this system"

5.2 test

The test command provides a way to test different conditions in an if-then statement. If the condition listed in the test command evaluates to true, the test command exits with a zero exit status code, making the if-then statement behave in much the same way that if-then statements work in other programming languages. If the condition is false, the test command exits with a 1, which causes the if-then statement to fail.

*) Numeric Comparisons

Comparison	Description
n1 -eq n2	Check if n1 is equal to n2.
n1 -ge n2	Check if n1 is greater than or equal to n2.
n1 -gt n2	Check if n1 is greater than n2.
n1 -le n2	Check if n1 is less than or equal to n2.
n1 -lt n2	Check if n1 is less than n2.
n1 -ne n2	Check if n1 is not equal to n2.

#!/bin/bash
val1=10
val2=11
if [ $val1 -gt $val2 ]; then
    echo "$val1 is greater than $val2"
else
    echo "$val1 is less than $val2"
fi
if (( $val1 > $val2 )); then
    echo "$val1 is greater than $val2"
else
    echo "$val1 is less than $val2"
fi

#!/bin/bash

val1=10

val2=11

if [ $val1 -gt $val2 ]; then

echo "$val1 is greater than $val2"

else

echo "$val1 is less than $val2"

if (( $val1 > $val2 )); then

echo "$val1 is greater than $val2"

else

echo "$val1 is less than $val2"

However, The test command wasn’t able to handle the floating-point value.
You may also notice usage of double parentheses. It provide advanced mathematical formulas for comparisons, no escape is needed in it:

Symbol	Description
val++	Post-increment
val–	Post-decrement
++val	Pre-increment
–val	Pre-decrement
!	Logical negation
∼	Bitwise negation
**	Exponentiation
<<	Left bitwise shift
>>	Right bitwise shift
&	Bitwise Boolean AND
\|	Bitwise Boolean OR
**	Exponentiation
&&	&& Logical AND
\|\|	Logical OR

*) String Comparisons

Comparison	Description
str1 = str2	Check if str1 is the same as string str2.
str1 != str2	Check if str1 is not the same as str2.
str1 < str2	Check if str1 is less than str2.
str1 > str2	Check if str1 is greater than str2.
-n str1	Check if str1 has a length greater than zero.
-z str1	Check if str1 has a length of zero.

Trying to determine if one string is less than or greater than another is where things start getting tricky. There are two problems that often plague shell programmers when trying to use the greater-than or less-than features of the test command:
– The greater-than and less-than symbols must be escaped, or the shell will use them as redirection symbols, with the string values as filenames.
– The greater-than and less-than order is not the same as that used with the sort command.

#!/bin/bash
val1=ben
val2=mike
if [ $val1 \> $val2 ]; then
    echo "$val1 is greater than $val2"
else
    echo "$val1 is less than $val2"
fi
if [[ $val1 > $val2 ]]; then
    echo "$val1 is greater than $val2"
else
    echo "$val1 is less than $val2"
fi

#!/bin/bash

val1=ben

val2=mike

if [ $val1 \> $val2 ]; then

echo "$val1 is greater than $val2"

else

echo "$val1 is less than $val2"

if [[ $val1 > $val2 ]]; then

echo "$val1 is greater than $val2"

else

echo "$val1 is less than $val2"

The double bracketed expression uses the standard string comparison used in the test command. However, it provides an additional feature that the test command doesn’t, pattern matching. No escape is needed anymore.

Capitalized letters are treated as less than lowercase letters in the test command. However, when you put the same strings in a file and use the sort command, the lowercase letters appear first. This is due to the ordering technique each command uses. The test command uses standard ASCII ordering, using each character’s ASCII numeric value to determine the sort order. The sort command uses the sorting order defined for the system locale language settings. For the English language, the locale settings specify that lowercase letters appear before uppercase letters in sorted order.

While the BashFAQ said: As of bash 4.1, string comparisons using < or > respect the current locale when done in [[, but not in [ or test. In fact, [ and test have never used locale collating order even though past man pages said they did. Bash versions prior to 4.1 do not use locale collating order for [[ either. So you get opposite result when running on CentOS-5.7(bash-3.2) and Ubuntu-10.04(bash-4.1) with [[ operator. And bash-4.1 is consistent with sort command now.

5.3 case

Well, this is easy, just walk through the snippet:

#!/bin/bash
case $USER in
gonwan | barbara)
    echo "Welcome, $USER"
    echo "Please enjoy your visit"
    ;;
testing)
    echo "Special testing account"
    ;;
jessica)
    echo "Do not forget to log off when you're done"
    ;;
*)
    echo "Sorry, you are not allowed here"
    ;;
esac

#!/bin/bash

case $USER in

gonwan | barbara)

echo "Welcome, $USER"

echo "Please enjoy your visit"

;;

testing)

echo "Special testing account"

;;

jessica)

echo "Do not forget to log off when you're done"

;;

echo "Sorry, you are not allowed here"

;;

esac

All sample code are tested under CentOS-5.7 and Ubuntu-10.04.

X11 Forwarding over SSH

October 3, 2011 by gonwan·0 Comments

First, you should install a SSH server:

# centos 5.7
# yum install openssh-server
# ubuntu 10.04
# sudo apt-get install openssh-server

# centos 5.7

# yum install openssh-server

# ubuntu 10.04

# sudo apt-get install openssh-server

The configure files are located in /etc/ssh/sshd_config. The default ones are OK.

Now connect your server by command below. The -X flag enables X11 forwarding, through which a user can access the local X11 display:

# ssh -X <user>@<address>

1	# ssh -X <user>@<address>

I use Ubuntu as host, and CentOS as guest in VirtualBox. The default NAT network mode does not allow you to access a guest from host. I just change the network mode to Host-only Network, and the problem is solved.

Here gives a screenshot: ubuntu-tweak is running on CentOS:

Using CIMPLE with OpenPegasus CIM Server

September 12, 2011 by gonwan·0 Comments

This post just walk through the usage of CIMPLE and OpenPegasus in CentOS 5.x. For background knowledge, please refer to wikipedia.

In CentOS 5.x, just install OpenPegasus(2.9.1) from yum:

# yum install tog-pegasus tog-pegasus-devel

1	# yum install tog-pegasus tog-pegasus-devel

We install the devel package since CIMPLE needs to build against it. I used CIMPLE 1.2.4. Before build it, we should fix broken symbolic links of OpenPegasus package, otherwise link error occurs:

# ln -s /usr/lib/libpegconfig.so.1 /usr/lib/libpegconfig.so
# ln -s /usr/lib/libpeglistener.so.1 /usr/lib/libpeglistener.so
# ln -s /usr/lib/libpegprm.so.1 /usr/lib/libpegprm.so
# ln -s /usr/lib/libpegprovidermanager.so.1 /usr/lib/libpegprovidermanager.so

# ln -s /usr/lib/libpegconfig.so.1 /usr/lib/libpegconfig.so

# ln -s /usr/lib/libpeglistener.so.1 /usr/lib/libpeglistener.so

# ln -s /usr/lib/libpegprm.so.1 /usr/lib/libpegprm.so

# ln -s /usr/lib/libpegprovidermanager.so.1 /usr/lib/libpegprovidermanager.so

There’s also a trivial bug which prevent CIMPLE from generating CMPI version of makefiles. Edit ${CIMPLE}/src/tools/genmak/main.cpp, find line “case ‘c'”, and change to “case ‘C'”. Now configure and make:

# ./configure --prefix=/usr --with-pegasus=/usr --with-cmpi=/usr/include/Pegasus/Provider/CMPI
# make
# make install

# ./configure --prefix=/usr --with-pegasus=/usr --with-cmpi=/usr/include/Pegasus/Provider/CMPI

# make

# make install

Aha!! Another annoying bug: wrong permissions in *.tar.gz source package. Fix with:

# chmod 644 /usr/share/cimple/mak/*.mak
# chmod 755 /usr/share/cimple/mak/*.sh

1 2	# chmod 644 /usr/share/cimple/mak/.mak # chmod 755 /usr/share/cimple/mak/.sh

Demo code refers to CIMPLE official tutorial. It can be found in source package. A repository.mof file is created first:

class President
{
    [Key] uint32 Number;
    string First;
    string Last;
};
class VicePresident
{
    [Key] uint32 Number;
    string First;
    string Last;
};

class President

{

[Key] uint32 Number;

string First;

string Last;

};

class VicePresident

{

[Key] uint32 Number;

string First;

string Last;

};

Run genproj to generate class files, provider files, and module files:

# genproj President President VicePresident

1	# genproj President President VicePresident

Generate makefiles using genmak. First line is for OpenPegasus adapter, while second line for CMPI adapter:

# genmak President *.cpp
# genmak -C President *.cpp

1 2	# genmak President .cpp # genmak -C President .cpp

We implemented President::get_instance() and President::enum_instance() in our code:

Get_Instance_Status President_Provider::get_instance(
    const President* model,
    President*& instance)
{
    /* return GET_INSTANCE_UNSUPPORTED;  */

    if (model->Number.value == 1)
    {
        instance = President::create(true);
        instance->Number.set(1);
        instance->First.set("George");
        instance->Last.set("Washington");
        return GET_INSTANCE_OK;
    }
    else if (model->Number.value == 2)
    {
        instance = President::create(true);
        instance->Number.set(2);
        instance->First.set("John");
        instance->Last.set("Adams");
        return GET_INSTANCE_OK;
    }
    else if (model->Number.value == 3)
    {
        instance = President::create(true);
        instance->Number.set(3);
        instance->First.set("Thomas");
        instance->Last.set("Jefferson");
        return GET_INSTANCE_OK;
    }

    return GET_INSTANCE_NOT_FOUND;
}

Enum_Instances_Status President_Provider::enum_instances(
    const President* model,
    Enum_Instances_Handler<President>* handler)
{
    President* instance;

    instance = President::create(true);
    instance->Number.set(1);
    instance->First.set("George");
    instance->Last.set("Washington");
    handler->handle(instance);

    instance = President::create(true);
    instance->Number.set(2);
    instance->First.set("John");
    instance->Last.set("Adams");
    handler->handle(instance);

    instance = President::create(true);
    instance->Number.set(3);
    instance->First.set("Thomas");
    instance->Last.set("Jefferson");
    handler->handle(instance);
    
    return ENUM_INSTANCES_OK;
}

Get_Instance_Status President_Provider::get_instance(

const President* model,

President*& instance)

{

/* return GET_INSTANCE_UNSUPPORTED; */

if (model->Number.value == 1)

{

instance = President::create(true);

instance->Number.set(1);

instance->First.set("George");

instance->Last.set("Washington");

return GET_INSTANCE_OK;

}

else if (model->Number.value == 2)

{

instance = President::create(true);

instance->Number.set(2);

instance->First.set("John");

instance->Last.set("Adams");

return GET_INSTANCE_OK;

}

else if (model->Number.value == 3)

{

instance = President::create(true);

instance->Number.set(3);

instance->First.set("Thomas");

instance->Last.set("Jefferson");

return GET_INSTANCE_OK;

}

return GET_INSTANCE_NOT_FOUND;

}

Enum_Instances_Status President_Provider::enum_instances(

const President* model,

Enum_Instances_Handler<President>* handler)

{

President* instance;

instance = President::create(true);

instance->Number.set(1);

instance->First.set("George");

instance->Last.set("Washington");

handler->handle(instance);

instance = President::create(true);

instance->Number.set(2);

instance->First.set("John");

instance->Last.set("Adams");

handler->handle(instance);

instance = President::create(true);

instance->Number.set(3);

instance->First.set("Thomas");

instance->Last.set("Jefferson");

handler->handle(instance);

return ENUM_INSTANCES_OK;

}

If get_instance() returns GET_INSTANCE_UNSUPPORTED, the adapter satisﬁes the request by calling enum_instances() and searching for a matching instances. It is recommend to leave get_instance() unsupported when the total number of instances is small.

After making your module, a registration is required for OpenPegasus CIM server. Start your server and register. The shared library should also be copied to OpenPegasus’s providers folder manually:

# cp libPresident.so /usr/lib/Pegasus/providers
# /etc/init.d/tog-pegasus start
# regmod -c ./libPresident.so
Using Pegasus C++ provider interface
Creating class VicePresident (root/cimv2)
Creating class President (root/cimv2)
Registering VicePresident_Provider (class VicePresident)
Registering President_Provider (class President)

# cp libPresident.so /usr/lib/Pegasus/providers

# /etc/init.d/tog-pegasus start

# regmod -c ./libPresident.so

Using Pegasus C++ provider interface

Creating class VicePresident (root/cimv2)

Creating class President (root/cimv2)

Registering VicePresident_Provider (class VicePresident)

Registering President_Provider (class President)

To unregister this provider, run:

# regmod -u -c ./libPresident.so
Using Pegasus C++ provider interface
Unregistering VicePresident_Provider (class VicePresident)
Deleted class VicePresident
Unregistering President_Provider (class President)
Deleted class President

# regmod -u -c ./libPresident.so

Using Pegasus C++ provider interface

Unregistering VicePresident_Provider (class VicePresident)

Deleted class VicePresident

Unregistering President_Provider (class President)

Deleted class President

You may want to dump MOF registration instance for your provide:

# regmod -d ./libPresident.so
instance of PG_ProviderModule
{
    Name = "President_Module";
    Vendor = "Pegasus";
    Version = "2.5.0";
    InterfaceType = "C++Default";
    InterfaceVersion = "2.5.0";
    Location = "President";
};

instance of PG_Provider
{
    Name = "VicePresident_Provider";
    ProviderModuleName = "President_Module";
};

instance of PG_ProviderCapabilities
{
    CapabilityID = "VicePresident";
    ProviderModuleName = "President_Module";
    ProviderName = "VicePresident_Provider";
    ClassName = "VicePresident";
    Namespaces = {"root/cimv2"};
    ProviderType = {2};
    supportedProperties = NULL;
    supportedMethods = NULL;
};

instance of PG_Provider
{
    Name = "President_Provider";
    ProviderModuleName = "President_Module";
};

instance of PG_ProviderCapabilities
{
    CapabilityID = "President";
    ProviderModuleName = "President_Module";
    ProviderName = "President_Provider";
    ClassName = "President";
    Namespaces = {"root/cimv2"};
    ProviderType = {2};
    supportedProperties = NULL;
    supportedMethods = NULL;
};

# regmod -d ./libPresident.so

instance of PG_ProviderModule

{

Name = "President_Module";

Vendor = "Pegasus";

Version = "2.5.0";

InterfaceType = "C++Default";

InterfaceVersion = "2.5.0";

Location = "President";

};

instance of PG_Provider

{

Name = "VicePresident_Provider";

ProviderModuleName = "President_Module";

};

instance of PG_ProviderCapabilities

{

CapabilityID = "VicePresident";

ProviderModuleName = "President_Module";

ProviderName = "VicePresident_Provider";

ClassName = "VicePresident";

Namespaces = {"root/cimv2"};

ProviderType = {2};

supportedProperties = NULL;

supportedMethods = NULL;

};

instance of PG_Provider

{

Name = "President_Provider";

ProviderModuleName = "President_Module";

};

instance of PG_ProviderCapabilities

{

CapabilityID = "President";

ProviderModuleName = "President_Module";

ProviderName = "President_Provider";

ClassName = "President";

Namespaces = {"root/cimv2"};

ProviderType = {2};

supportedProperties = NULL;

supportedMethods = NULL;

};

Install command line utilities and test OpenPegasus server:

# yum install sblim-wbemcli
# yum install sblim-cmpi-base
# wbemcli ecn https://<user>:<pass>@localhost:5989/root/cimv2
# wbemcli -nl ei https://<user>:<pass>@localhost:5989/root/cimv2:Linux_Processor

# yum install sblim-wbemcli

# yum install sblim-cmpi-base

# wbemcli ecn https://<user>:<pass>@localhost:5989/root/cimv2

# wbemcli -nl ei https://<user>:<pass>@localhost:5989/root/cimv2:Linux_Processor

Test our President provider:

# wbemcli ei https://<user>:<pass>@localhost:5989/root/cimv2:President
localhost:5989/root/cimv2:President.Number=1 Number=1,First="George",Last="Washington"
localhost:5989/root/cimv2:President.Number=2 Number=2,First="John",Last="Adams"
localhost:5989/root/cimv2:President.Number=3 Number=3,First="Thomas",Last="Jefferson"
# wbemcli gi https://<user>:<pass>@localhost:5989/root/cimv2:President.Number=1
localhost:5989/root/cimv2:President.Number="1" Number=1,First="George",Last="Washington"

# wbemcli ei https://<user>:<pass>@localhost:5989/root/cimv2:President

localhost:5989/root/cimv2:President.Number=1 Number=1,First="George",Last="Washington"

localhost:5989/root/cimv2:President.Number=2 Number=2,First="John",Last="Adams"

localhost:5989/root/cimv2:President.Number=3 Number=3,First="Thomas",Last="Jefferson"

# wbemcli gi https://<user>:<pass>@localhost:5989/root/cimv2:President.Number=1

localhost:5989/root/cimv2:President.Number="1" Number=1,First="George",Last="Washington"

All code can be found in my skydrive here:

Learning Bash Scripts (1)

August 28, 2011 by gonwan·0 Comments

In this first post of the series, some basic concepts are introduced. All information from Linux Command Line and Shell Scripting Bible, Second Edition.

1. Shell Types

There are three ways of starting a bash shell:
– As a default login shell at login time
– As an interactive shell that is not the login shell
– As a non-interactive shell to run a script

Login Shell

When you log in to the Linux system, the bash shell starts as a login shell. The login shell looks for four different startup files to process commands from. The following is the order in which the bash shell processes the files:

– /etc/profile
– $HOME/.bash_profile
– $HOME/.bash_login
– $HOME/.profile

Interactive Shell

If you start a bash shell without logging into a system (such as if you just type bash at a CLI prompt), you start what’s called an interactive shell. The interactive shell doesn’t act like the login shell, but it still provides a CLI prompt for you to enter commands.

If bash is started as an interactive shell, it doesn’t process the /etc/profile file. Instead, it checks for the .bashrc file in the user’s HOME directory.

Non-interactive Shell

Finally, the last type of shell is a non-interactive shell. This is the shell that the system starts to execute a shell script. This is different in that there isn’t a CLI prompt to worry about. However, there may still be specific startup commands you want to run each time you start a script on your system.

To accommodate that situation, the bash shell provides the BASH_ENV environment variable. When the shell starts a non-interactive shell process, it checks this environment variable for the name of a startup file to execute. If one is present, the shell executes the commands in the file.

2. Terminfo Database

The terminfo database is a set of files that identify the characteristics of various terminals that can be used on the Linux system. The Linux system stores the terminfo data for each terminal type as a separate file in the terminfo database directory. The location of this directory often varies from distribution to distribution. Some common locations are /usr/share/terminfo, /etc/terminfo, and /lib/terminfo.

Since the terminfo database files are binary, you cannot see the codes within these files. However, you can use the infocmp command to convert the binary entries into text.

The Linux shell uses the TERM environment variable to define which terminal emulation setting in the terminfo database to use for a specific session. When the TERM environment variable is set to vt100, the shell knows to use the control codes associated with the vt100 terminfo database entry for sending control codes to the terminal emulator.

3. Virtual Consoles

With modern Linux systems, when the Linux system starts it automatically creates several virtual consoles. A virtual console is a terminal session that runs in memory on the Linux system. Instead of having several dumb terminals connected to the PC, most Linux distributions start seven (or sometimes even more) virtual consoles that you can access from the single PC keyboard and monitor.

In most Linux distributions, you can access the virtual consoles using a simple keystroke combination. Usually you must hold down the Ctl+Alt key combination, and then press a function key (F1 through F8) for the virtual console you want to use. Function key F1 produces virtual console 1, key F2 produces virtual console 2, and so on.

4. Environment Variables

There are two types of environment variables in the bash shell:
– Global variables
– Local variables

Global environment variables are visible from the shell session, and from any child processes that the shell spawns. Local variables are only available in shell that creates them. This makes global environment variables useful in applications that spawn child processes that require information from the parent process.

Get

To view the global environment variables, use the printenv command.
To display the value of an individual environment variable, use the echo command. When referencing an environment variable, you must place a dollar sign($) before the environment variable name.

Unfortunately there isn’t a command that displays only local environment variables. The set command displays all of the environment variables set for a specific process. However, this also includes the global environment variables.

Set

You can assign either a numeric or a string value to an environment variable by assigning the variable to a value using the equal sign(=). It’s extremely important that there are no spaces between the environment variable name, the equal sign, and the value. If you put any spaces in the assignment, the bash shell interprets the value as a separate command.

The method used to create a global environment variable is to create a local environment variable and then export it to the global environment.

Of course, if you can create a new environment variable, it makes sense that you can also remove an existing environment variable. You can do this with the unset command.When referencing the environment variable in the unset command, remember not to use the dollar sign.

NOTE: When dealing with global environment variables, things get a little tricky. If you’re in a child process and unset a global environment variable, it applies only to the child process. The global environment variable is still available in the parent process.