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Mike Translating
Practical Interview Questions and Answers on Linux Shell Scripting
================================================================================
With the overwhelming response we are getting on the Interview Series articles, the first of its kind on any Linux How-to website in the form of Likes, Feedbacks in comment as well as on personal Email Address make us going from one article to the next article.
Here is the link to the [Interview Series][1] articles already published on Tecmint.com, where we have covered lots of topics viz., FTP, MySQL, Apache, Scripting, Linux Commands, etc.
![Practical Interview Question on Shell Scripting](http://www.tecmint.com/wp-content/uploads/2014/06/Interview-Questions-on-Shell-Scripting.png)
Practical Interview Question on Shell Scripting
Continuing to the above series here we are coming with another 5 wonderful Linux Interview Questions and their answer. Your (The Tecmint.com Readers and frequent Visitors) support is always needed to make it successful.
### 1. Write a shell script to get current date, time, user name and current working directory. ###
> **Answer** : The commands logname, date, who I am and pwd will output username, current date and time, and current working directory. Just implementing these commands in the script and making it a bit interactive.
Now create a file called ‘**userstats.sh**‘ and add the following code to it.
#!/bin/bash
echo "Hello, $LOGNAME"
echo "Current date is `date`"
echo "User is `who i am`"
echo "Current directory `pwd`"
Place execute permission and run the script as shown below.
# chmod 755 userstats.sh
# ./userstats.sh
#### Sample Output ####
Hello, avi
Current date is Sat Jun 7 13:05:29 IST 2014
User is avi pts/0 2014-06-07 11:59 (:0)
Current directory /home/avi/Desktop
### 2. Write a Shell Script that adds two numbers if provided as the command Line Argument and if the two numbers are not entered it outputs an Error Message along with a one-Line of how-to use description. ###
> **Answer** : Here is the simple Shell Script along with description which adds two number if provided as Command-Line argument, if not it throws error with single line on how to use the script.
Again create a file called ‘**two-numbers.sh**‘ and add the following content to it.
#!/bin/bash
# The Shebang
if [ $# -ne 2 ]
# If two Inputs are not received from Standard Input
then
# then execute the below statements
echo "Usage - $0 x y"
# print on standard output, how-to use the script (Usage - ./1.sh x y )
echo " Where x and y are two nos for which I will print sum"
# print on standard output, “Where x and y are two nos for which I will print sum ”
exit 1
# Leave shell in Error Stage and before the task was successfully carried out.
fi
# End of the if Statement.
echo "Sum of $1 and $2 is `expr $1 + $2`"
# If the above condition was false and user Entered two numbers as a command Line Argument,
it will show the sum of the entered numbers.
Set executer permission on the file and run the script as shown below.
# chmod 755 two-numbers.sh
**Condition 1**: Running the script without entering two numbers as command line argument, you will get the following output.
#### Sample Output ####
# ./two-numbers.sh
Usage - ./two-numbers.sh x y
Where x and y are two nos for which I will print sum
**Condition 2**: When Numbers are entered as command line argument you will get the result as shown.
$ ./two-numbers.sh 4 5
Sum of 4 and 5 is 9
Hence the above shell script fulfills the condition as suggested in the question.
### 3. You needs to print a given Number say 10572, in reverse order using a Shell script such that the input is provided using command Line Argument only. If the input data is not provided as Command Line Argument, it should throw and error and should suggest, how to use the script. Write the script but before that tell me the algorithm that needs to be implemented here. ###
#### Algorithm ####
1. Let the Input Number = n
1. Set rev=0, sd=0 (Reverse and single digitis set to 0)
1. n % 10, will find and give single left most digit
1. reverse number is generated as rev * 10 + sd
1. Decrease Input Number (n) by 1.
1. if n > 0, then goto step 3 else goto setp 7
1. Print rev
Now again, create a file called ‘**numbers.sh**‘ and add the following given code it.
#!/bin/bash
if [ $# -ne 1 ]
then
echo "Usage: $0 number"
echo " I will find reverse of given number"
echo " For eg. $0 0123, I will print 3210"
exit 1
fi
n=$1
rev=0
sd=0
while [ $n -gt 0 ]
do
sd=`expr $n % 10`
rev=`expr $rev \* 10 + $sd`
n=`expr $n / 10`
done
echo "Reverse number is $rev"
Grant a execute permission on the file and run the script as shown below.
# chmod 755 numbers.h
**Condition 1**: When Input is not provided as command line argument, you will get the following output.
#### Sample Output ####
./numbers.sh
Usage: ./numbers.sh number
I will find reverse of given number
For eg. ./2.sh 123, I will print 321
**Condition 2**: When Input was provided as command line Argument.
$ ./numbers.sh 10572
Reverse number is 27501
The above script worked perfectly and the output was just what we needed.
### 4. You are supposed to calculate a real number calculation directly from terminal and not any shell script. What will you do (say the real numbers are 7.56 and 2.453)? ###
> **Answer** : We need to use bc command in a special way as described below. The output of echo 7.56 + 2.453 should be pipelined to bc.
For example, run the following command to calculate numbers in real time using bc command as shown.
$ echo 7.56 + 2.453 | bc
10.013
### 5. You are supposed to find the value of pi upto 100 places of decimal, what is the easiest way to get the result done. ###
> **Answer** : The easiest way to find the value of pi, correct upto 100 places of decimal we just need to issue the below command.
# pi 100
3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067
Obviously! We must have package ‘**pi**‘ installed. Just do a **apt** or **yum** to get a required package to install ‘**pi**‘ onto the distribution you are using.
That’s all for now. I’ll be here again with another interesting article very soon. Till then stay tuned and connected to Tecmint.com. Don’t forget to provide us with you valuable feedback in the comment section below.
--------------------------------------------------------------------------------
via: http://www.tecmint.com/practical-interview-questions-on-linux-shell-scripting/
译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
[1]:http://www.tecmint.com/category/interview-questions/

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实用的Linux SHELL面试问题及答案
================================================================================
随着之前有关面试的系列文章，读者的反应比较强烈，所以我决定出一篇有关Linux Shell相关的面试文章，如果对本文有什么意见或意见的话，欢迎反馈到我的邮箱里。
如果想要阅读已发表在Tecmint.com的文章，可以点击链接，链接到[访谈系列] [1]，在这里我们已经介绍很多题目即文章。，FTP，MySQL和Apache的，脚本，Linux命令等。
![Practical Interview Question on Shell Scripting](http://www.tecmint.com/wp-content/uploads/2014/06/Interview-Questions-on-Shell-Scripting.png)
> 实用的shell脚本面试问题
这边提到的5个面试问题，延续之前的有关Linux面试问题和答案。如果你是Tecmint.com的读者，你的支持我非常感谢。
### 1. 写一个shell脚本来得到当前的日期，时间，用户名和当前工作目录。 ###
> **Answer** : 将输出用户名，当前日期和时间，以及当前工作目录的命令就是logname，date，who i am和pwd。
现在，创建一个名为**`userstats.sh`**文件，将下面的代码添加到它。
#!/bin/bash
echo "Hello, $LOGNAME"
echo "Current date is `date`"
echo "User is `who i am`"
echo "Current directory `pwd`"
给他添加执行权限，并且执行他。
# chmod 755 userstats.sh
# ./userstats.sh
#### 样例输出 ####
Hello, avi
Current date is Sat Jun 7 13:05:29 IST 2014
User is avi pts/0 2014-06-07 11:59 (:0)
Current directory /home/avi/Desktop
### 2.写一个shell脚本，进行两个数字的相加，如果没有输入参数就输出错误信息和使用说明的###
> **Answer** :
下面是简单的shell脚本以及描述，如果没有命令行参数，它会抛出错误与如何使用脚本的说明。
再创建一个名为**`twonumbers.sh`**文件和下面的内容添加到文件里。
#!/bin/bash
# The Shebang
if [ $# -ne 2 ]
# If two Inputs are not received from Standard Input
then
# then execute the below statements
echo "Usage - $0 x y"
# print on standard output, how-to use the script (Usage - ./1.sh x y )
echo " Where x and y are two nos for which I will print sum"
# print on standard output, “Where x and y are two nos for which I will print sum ”
exit 1
# Leave shell in Error Stage and before the task was successfully carried out.
fi
# End of the if Statement.
echo "Sum of $1 and $2 is `expr $1 + $2`"
# If the above condition was false and user Entered two numbers as a command Line Argument,
it will show the sum of the entered numbers.
给他添加可执行权限，并且执行。
# chmod 755 two-numbers.sh
**Condition 1**: 未输入两个数字作为命令行参数运行脚本，你将得到下面的输出。
#### Sample Output ####
# ./two-numbers.sh
Usage - ./two-numbers.sh x y
Where x and y are two nos for which I will print sum
**Condition 2**: 当数字存在时，你会得到如图所示的结果。
$ ./two-numbers.sh 4 5
Sum of 4 and 5 is 9
因此，上述shell脚本满足条件作为问题提出了建议。
### 3.你需要打印一个给定的数字的反序，如输入10572，输出27501，如果没有输入数据，应该抛出错误和使用脚本说明。在此之前，告诉我，你需要在这里使用的算法。 ###
#### 算法 ####
1. 输入的数字为n
2. 赋值 rev=0, sd=0 (反向和单个数字设置为0)
3. n % 10, 将得到最左边的数字
4. 反向数字可以用这个方法生成 rev * 10 + sd
5. 对输入数字进行-1操作
6. 如果n > 0, 进入第三步，否则进行第七步
7. 输出rev
现在，创建一个名为**`numbers.sh**`文件，并添加以下代码。
#!/bin/bash
if [ $# -ne 1 ]
then
echo "Usage: $0 number"
echo " I will find reverse of given number"
echo " For eg. $0 0123, I will print 3210"
exit 1
fi
n=$1
rev=0
sd=0
while [ $n -gt 0 ]
do
sd=`expr $n % 10`
rev=`expr $rev \* 10 + $sd`
n=`expr $n / 10`
done
echo "Reverse number is $rev"
授予对文件的执行权限，并运行如下所示的脚本。
# chmod 755 numbers.h
**Condition 1**: 当输入不包含命令行参数，你将得到下面的输出。
#### Sample Output ####
./numbers.sh
Usage: ./numbers.sh number
I will find reverse of given number
For eg. ./2.sh 123, I will print 321
**Condition 2**: 正常输入
$ ./numbers.sh 10572
Reverse number is 27501
上面的脚本非常完美，输出正是我们需要的。
### 4. 你应该直接用终端，而不是依靠任何shell脚本来进行实数计算。你会怎么做（比如实数7.56+2.453）？ ###
> **Answer** :
我们需要用如下所述的特殊方式使用bc命令。将7.56+2.453作为输入通过管道进入bc中。
$ echo 7.56 + 2.453 | bc
10.013
### 5. 你需要给出圆周率的值，精度为小数点后100位，什么是最简单的方法。 ###
> **Answer** : 找圆周率的值最简单的方法，我们只是需要发出以下命令。
# pi 100
3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067
很明显！安装我们必须有包**`pi`**。只是一个**apt**或**yum**命令，就能获得所需的软件包，同时用最简单方法来实现这个需求。
就是这样。我会很快在Tecmint.com发表另一个有趣的文章。至此敬请关注。别忘了向我们提供您在的评论和反馈。
--------------------------------------------------------------------------------
via: http://www.tecmint.com/practical-interview-questions-on-linux-shell-scripting/
译者：[MikeCoder](https://github.com/MikeCoder) 校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
[1]:http://www.tecmint.com/category/interview-questions/