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<\/figure>\n\n\n\nIn computer programing, a script could be a set of commands for an applicable run time atmosphere that is employed to alter the execution of tasks.<\/p>\n\n\n\n
Bash Script:<\/strong><\/p>\n\n\n\n A Bash Shell Script could be a plain document containing a group of assorted commands that we have a tendency to typically sort within the command. Its accustomed alter repetitive tasks on UNIX system filesystem. It would embody a group of commands, or one command, or it would contain the hallmarks of imperative programming like loops, functions, conditional constructs, etc. Effectively, a Bash script could be a bug written within the Bash artificial language.<\/p>\n\n\n\n We had discussed the bash, script and bash scripting. Now, let’s move on to the FAQ’s and interview questions of Bash scripting.<\/p>\n\n\n\n Interview questions and answers for Bash scripting<\/strong>:-<\/p>\n\n\n\n The bash script is a shell programming language. Generally, we run many types of shell commands from the terminal by typing each command separately that require time and efforts. If we need to run the same commands again then we have to execute all the commands from the terminal again. But using a bash script, we can store many shell command statements in a single bash file and execute the file any time by a single command. Many system administration related tasks, program installation, disk backup, evaluating logs, etc. can be done by using proper bash script.<\/p>\n\n\n\n 2. What are the advantages of using bash scripts?<\/strong><\/p>\n\n\n\n Bash script has many advantages which are described below:<\/p>\n\n\n\n 3. Mention the disadvantages of bash scripts<\/strong><\/p>\n\n\n\n Some disadvantages of bash script are mentioned below:<\/p>\n\n\n\n 4. What types of variables are used in bash?<\/strong><\/p>\n\n\n\n Two types of variables can be used in bash script. These are:<\/p>\n\n\n\n System variables<\/p>\n\n\n\n The variables which are pre-defined and maintained by the Linux operating system are called system variables. These type of variables are always used by an uppercase letter. The default values of these variables can be changed based on requirements.<\/p>\n\n\n 5<\/strong>. How to declare and delete variables in bash?<\/strong><\/p>\n\n\n\n The variable can be declared in bash by data type or without data type. If any bash variable is declared without declare command, then the variable will be treated as a string. Bash variable is declared with declare command to define the data type of the variable at the time declaration.<\/p>\n\n\n 6. How to add comments in a bash script?<\/strong><\/p>\n\n\n\n Single line and multi-line comments can be used in bash script. \u2018#\u2018 symbol is used for single-line comment. \u2018<<\u2019 symbol with a delimiter and \u2018:\u2019 with single (\u2018) are used for adding multi-line comment.<\/p>\n\n\n\n Example:<\/p>\n\n\n 7. How can you combine strings in a bash script?<\/strong><\/p>\n\n\n\n String values can be combined in bash in different ways. Normally, the string values are combined by placing together but there are other ways in bash to combine string data.<\/p>\n\n\n\n Example:<\/p>\n\n\n\n #!\/bin\/bash<\/p>\n\n\n\n #Initialize the variables<\/p>\n\n\n\n str1=”PHP”<\/p>\n\n\n\n str2=”Bash”<\/p>\n\n\n\n str3=”Perl”<\/p>\n\n\n\n # Print string together with space<\/p>\n\n\n\n echo $str1 $str2 $str3<\/p>\n\n\n\n #Combine all variables and store in another variable<\/p>\n\n\n\n str=”$str1, $str2 and $str3″<\/p>\n\n\n\n #Combine other string data with the existing value of the string<\/p>\n\n\n\n str+=” are scripting languages”<\/p>\n\n\n\n #Print the string<\/p>\n\n\n\n echo $str<\/p>\n\n\n\n 8. Which commands are used to print output in bash?<\/strong><\/p>\n\n\n\n `echo` and `printf` commands can be used to print output in bash. `echo` command is used to print the simple output and `printf` command is used to print the formatted output.<\/p>\n\n\n\n Example:<\/p>\n\n\n 9. How to use command-line arguments in bash?<\/strong><\/p>\n\n\n\n Command-line arguments are read by $1, $2, $3\u2026$n variables. Command-line argument values are provided in the terminal when executing the bash script. $1 is used to read the first argument, $2 is used to read the second argument and so on.<\/p>\n\n\n\n #!\/bin\/bash<\/p>\n\n\n\n #Check any argument is provided or not<\/p>\n\n\n\n if [[ $# -eq 0 ]]; then<\/p>\n\n\n\n echo “No argument is given.”<\/p>\n\n\n\n exit 0<\/p>\n\n\n\n fi<\/p>\n\n\n\n #Store the first argument value<\/p>\n\n\n\n color=$1<\/p>\n\n\n\n # Print the argument with other string<\/p>\n\n\n\n printf “You favorite color is %s\\n” $color<\/p>\n\n\n\n 10. What are the advantages and disadvantages of Bash Scripting?<\/strong><\/p>\n\n\n\n Advantages<\/strong><\/p>\n\n\n\n Disadvantages<\/strong><\/p>\n\n\n\n 11. Explain about \u201cs\u201d permission bit in a file?<\/strong><\/p>\n\n\n\n \u201cS\u201d bit is called \u201cset user id\u201d (SUID) bit.<\/p>\n\n\n\n \u201cS\u201d bit on a file causes the process to have the privileges of the owner of the file during the instance of the program.<\/p>\n\n\n\n For example, executing \u201cpassed\u201d command to change current password causes the user to writes its new password to shadow file even though it has \u201croot\u201d as its owner.<\/p>\n\n\n\n 12. Create a directory such that anyone in the group can create a file and access any person\u2019s file in it but none should be able to delete a file other than the one created by himself.<\/strong><\/p>\n\n\n\n We can create the directory giving read and execute access to everyone in the group and setting its sticky bit \u201ct\u201d on as follows:<\/p>\n\n\n 13. How can you find out how long the system has been running?<\/strong><\/p>\n\n\n\n We can find this by using the command \u201cuptime\u201d.<\/p>\n\n\n\n 14. How can any user find out all information about a specific user like his default shell, real-life name, default directory, when and how long he has been using the system?<\/strong><\/p>\n\n\n 15. What is the difference between $$ and $!?<\/strong><\/p>\n\n\n\n $$ gives the process id of the currently executing process whereas $! Shows the process id of the process that recently went into the background.<\/p>\n\n\n\n 16. mWhat are zombie processes?<\/strong><\/p>\n\n\n\n These are the processes which have died but whose exit status is still not picked by the parent process. These processes even if not functional still have its process id entry in the process table.<\/p>\n\n\n\n 17. How will you copy a file from one machine to other?<\/strong><\/p>\n\n\n\n We can use utilities like \u201cftp,\u201d \u201cscp\u201d or \u201crsync\u201d to copy a file from one machine to other.<\/p>\n\n\n\n E.g., Using ftp:<\/p>\n\n\n 18. I want to monitor a continuously updating log file, what command can be used to most efficiently achieve this?<\/strong><\/p>\n\n\n\n We can use tail \u2013f filename. This will cause only the default last 10 lines to be displayed on std o\/p which continuously shows the updating part of the file.<\/p>\n\n\n\n 19. I want to connect to a remote server and execute some commands, how can I achieve this?<\/strong><\/p>\n\n\n\n We can use ssh to do this:<\/p>\n\n\n\n ssh username@serverIP -p sshport<\/p>\n\n\n\n Example<\/p>\n\n\n Once above command is executed, you will be asked to enter the password<\/p>\n\n\n\n 20. I have 2 files and I want to print the records which are common to both.<\/strong><\/p>\n\n\n\n We can use tail \u2013f filename. This will cause only the default last 10 lines to be displayed on std o\/p which continuously shows the updating part of the file.<\/p>\n\n\n\n 21. I want to connect to a remote server and execute some commands, how can I achieve this?<\/strong><\/p>\n\n\n\n We can use ssh to do this:<\/p>\n\n\n\n ssh username@serverIP -p sshport Example<\/p>\n\n\n 22. I have 2 files and I want to print the records which are common to both.<\/strong><\/p>\n\n\n\n We can use \u201ccomm\u201d command as follows:<\/p>\n\n\n\n comm -12 file1 file2 \u2026 12 will suppress the content which are<\/p>\n\n\n\n unique to 1st and 2nd file respectively.<\/p>\n\n\n\n 23. Write a script to print the first 10 elements of Fibonacci series.<\/strong><\/p>\n\n\n 24. How will you connect to a database server from Linux?<\/strong><\/p>\n\n\n\n We can use isql utility that comes with open client driver as follows:<\/p>\n\n\n\n isql \u2013S serverName \u2013U username \u2013P password<\/p>\n\n\n\n 25. What are the 3 standard streams in Linux?<\/strong><\/p>\n\n\n\n 0 \u2013 Standard Input1 \u2013 Standard Output2 \u2013 Standard Error<\/p>\n\n\n\n 26. I want to read all input to the command from file1 direct all output to file2 and error to file 3, how can I achieve this?<\/strong><\/p>\n\n\n\n command <file1 1>file2 2>file3<\/p>\n\n\n\n 27. What will happen to my current process when I execute a command using exec?<\/strong><\/p>\n\n\n\n \u201c<\/strong>exec\u201d overlays the newly forked process on the current process; so when I execute the command using exec, the command gets executed on the current shell without creating any new processes.<\/p>\n\n\n\n E.g., Executing \u201cexec ls\u201d on command prompt will execute ls and once ls exits, the process will shut down<\/p>\n\n\n\n 28. How will you emulate wc \u2013l using awk?<\/strong><\/p>\n\n\n 29. Given a file find the count of lines containing the word \u201cABC\u201d.<\/strong><\/p>\n\n\n 30. ![\"\"](\"https:\/\/www.devopsschool.com\/blog\/wp-content\/uploads\/2022\/02\/QfP3Z.png\")
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<\/figure>\n\n\n\n\n`set`, `env` and<\/span> `printenv` commands can be used to print<\/span> the list<\/span> of system variables.\n#!\/bin\/bash<\/span>\n# Printing System Variables<\/span>\n \n#Print Bash shell name<\/span>\necho<\/span> $BASH\n \n# Print Bash shell Version<\/span>\necho<\/span> $BASH_VERSION\n \n# Print Home directory name<\/span>\necho<\/span> $HOME\n\n<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n\u2013r, -i, -a, -A, -l, -u, -t and<\/span> \u2013x options can be used with declare<\/span> command to declare<\/span> a variable with different data types.\n\n#!\/bin\/bash<\/span>\n \n#Declare variable without any type<\/span>\nnum=10<\/span>\n \n#Values will be combined but not added<\/span>\nresult=$num+20<\/span>\necho<\/span> $result\n \n#Declare variable with integer type<\/span>\ndeclare<\/span> -i num=10<\/span>\n \n#Values will be added<\/span>\ndeclare<\/span> -i result=num+20<\/span>\necho<\/span> $result\n\n<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n#!\/bin\/bash<\/span>\n#Print the text [Single line comment]<\/span>\necho<\/span> \"Bash Programming\"<\/span>\n<<addcomment\nCalculate the sum\nOf two numbers [multiline comment]\naddcomment\nnum=25<\/span>+35<\/span>\necho<\/span> $num\n: '\nCombine two\nString data [multiline comment]\n'<\/span>\nString=\"Hello\"<\/span>\necho<\/span> $string\" World\"<\/span>\n<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n#!\/bin\/bash<\/span>\n \n#Print the text<\/span>\necho<\/span> \"Welcome to LinuxHint\"<\/span>\nsite=\"linuxhint.com\"<\/span>\n#Print the formatted text<\/span>\nprintf \"%s is a popular blog site\\n\"<\/span> $site\n\nHow to take input from the terminal in bash?\n`read` command is used in a bash script to take input from the terminal.\n\n#!\/bin\/bash<\/span>\n#Print message<\/span>\necho<\/span> \"Enter your name\"<\/span>\n#Take input from the user<\/span>\nread name\n# Print the value of $name with other string<\/span>\necho<\/span> \"Your name is $name\"<\/span>\n<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n\n
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mkdir direc1\nchmod g+wx direc1\nchmod +t direc1\n\n<\/code><\/span><\/pre>\n\n\nfinger \u201cloginName\u201d \u2026where loginName is the login name of the\n\nuser whose information is expected.\n<\/code><\/span><\/pre>\n\n\nFTP hostname\n>put file1\n>bye\n\nAbove copies, file file1 from<\/span> the local system to destination system whose hostname is specified.\n<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\nssh<\/span> root<\/span>@122<\/span>.52.251.171 -p 22<\/span><\/code><\/span>Code language:<\/span> CSS<\/span> (<\/span>css<\/span>)<\/span><\/small><\/pre>\n\n\nssh<\/span> root<\/span>@122<\/span>.52.251.171 -p 22<\/span>\nOnce above command is executed, you will be asked to enter the password\n<\/code><\/span>Code language:<\/span> CSS<\/span> (<\/span>css<\/span>)<\/span><\/small><\/pre>\n\n\n#!\/bin\/sh<\/span>\na=1<\/span>\nb=1<\/span>\necho<\/span> $a\necho<\/span> $b\nfor<\/span> I in 1<\/span> 2<\/span> 3<\/span> 4<\/span> 5<\/span> 6<\/span> 7<\/span> 8<\/span>\ndo<\/span>\nc=a\nb=$a\nb=$(($a+$c))\necho<\/span> $b\ndone\n<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\nawk \u2018END {print<\/span> NR} fileName\u2019<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\ngrep \u2013c \u201cABC\u201d file1<\/code><\/span><\/pre>\n\n\n