Shulou(Shulou.com)06/03 Report--

This article mainly introduces what the Shell script test questions are, which have a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand.

1) how do I pass parameters to a script?

. / script argument

Example: show file name script

. / show.sh file1.txtcat show.shemaking raceme binbinarbashecho $1

(LCTT translation note: thank you for the reminder of an anonymous visitor, the original question is wrong, correct it. )

2) how to use parameters in a script?

The first parameter: $1, and the second parameter: $2

Example: the script copies the file (arg1) to the destination address (arg2)

. / copy.sh file1.txt / tmp/cat copy.shedding cards bind Bingray BASHCP $1 $2

3) how to calculate the parameters passed in?

$#

4) how do I get the script name in the script?

, 0

5) how to check whether the previous command was run successfully?

$?

6) how do I get the last line of the file?

Tail-1

7) how do I get the first line of the file?

Head-1

8) how do I get the third element of each line of a file?

Awk' {print $3}'

9) if the first element of each line in the file is FIND, how to get the second element

Awk' {if ($1 = = "FIND") print $2}'

10) how to debug bash scripts

Add the-xv parameter to #! / bin/bash

Example:

#! / bin/bash-xv

11) for example, how to write a function?

Function example {echo "Hello world!"}

12) how to concatenate two strings to?

V1 = "Hello" V2 = "World" V3 ${V1} ${V2} echo $V3

Output

HelloWorld

13) how to add two integers?

V1=1V2=2let V3=$V1+$V2echo $V3

Output

three

According to @ kashu, the better answer to this question is:

There are several ways to add two integers:

A=5B=6echo $(($Avalanche B)) # method 2echo $[$obtainable B] # method 3expr $obtainable B # method 4echo $Avalanche B | bc # method 5awk 'BEGIN {$A' +'"$B"'}'# method 6

14) how do I check if a file exists in the file system?

If [- f / var/log/messages] thenecho "File exists" fi

15) write all the loop syntax in the shell script?

For loop:

Foriin$ (ls); doecho item:$idone

While loop:

#! / bin/bashCOUNTER=0while [$COUNTER-lt 10]; doecho The counter is $COUNTERlet COUNTER=COUNTER+1done

Until loop:

#! / bin/bashCOUNTER=20until [$COUNTER- lt 10]; doecho COUNTER $COUNTERlet COUNTER-=1done

16) what does the #! / bin/sh or #! / bin/bash at the beginning of each script mean?

This line describes the shell to be used. #! / bin/bash indicates that the script uses / bin/bash. For python scripts, that is

#! / usr/bin/python .

17) how do I get line 10 of a text file?

Head-10 file | tail-1

18) what is the first symbol of the bash script file

#

19) Command: [- z ""] & & echo 0 | | what is the output of echo 1?

0

20) what is the use of ordering "export"?

Make the variable available in the child shell.

21) how do I run a script in the background?

Add "&" after the script.

According to @ kashu, the better answer is:

Nohup command&

Most of the time we may use Linux remotely. I have encountered command running in the background due to network outage.

22) what does "chmod 500 script" do?

Give the script owner executable permissions.

23) what does ">" do?

Redirect the output stream to a file or to another stream.

24) what's the difference between & and &

&-you want the script to use it when it runs in the background

& &-use the current script when it completes successfully before executing subsequent commands / scripts

25) when should I use "if" before [condition]?

When you need to run multiple commands when the conditions are met.

26) Command: what is the output of name=John & & echo'My name is $name'

Variable

27) which symbol is used for annotations in bash shell scripts?

#

28) Command: what is the output of echo ${new:-variable}

Variable

29) what's the difference between quotation marks and quotation marks?

'- use it when we don't want to convert a variable to a value.

"- calculate the values of all variables and replace them with values.

30) how do I redirect standard output and standard error streams to log.txt files in a script file?

Add the "exec > log.txt 2 > & 1" command to the script file.

31) how do I use the echo command to get only a portion of a string variable?

Echo ${variable:x:y} x-start position y-length

Example:

Variable= "My name is Petras, and I am developer." echo ${variable:11:6} # will display Petras

32) if the string variable= "User:123:321:/home/dir" is given, how can I just use the echo command to get home_dir?

Echo ${variable#*:}

Or

Echo ${variable##*:}

33) how do I get "User" from the above string?

Echo ${variable%:*}

Or

Echo ${variable%%:*}

34) how do I use awk to list users whose UID is less than 100?

Awk-F:'$3

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