![\"shell-programming-interview\"](\"http:\/\/www.scmgalaxy.com\/tutorials\/wp-content\/uploads\/2010\/04\/shell-programming-interview.png\")
<\/h3>\n<\/h3>\nHow do you find out what\u2019s your shell? <\/b>
\nAnswer: echo $SHELL<\/p>\n
What\u2019s the command to find out today\u2019s date? <\/b>
\nAnswer: date<\/p>\n
\u00a0What\u2019s the command to find out users on the system? <\/b>
\nAnswer: who<\/p>\n
How do you find out the current directory you\u2019re in? <\/b>
\nAnswer: pwd<\/p>\n
How do you remove a file? <\/b>
\nAnswer: rm<\/p>\n
How do you remove a file?<\/b>
\nAnswer: rm -rf<\/p>\n
How do you find out your own username? <\/b>
\nAnswer: whoami<\/p>\n
How do you send a mail message to somebody? <\/b>
\nAnswer: mail somebody@techinterviews.com -s \u2018Your subject\u2019 -c \u2018cc@techinterviews.com\u2018<\/p>\n
How do you count words, lines and characters in a file? <\/b>
\nAnswer: wc<\/p>\n
How do you search for a string inside a given file? <\/b>
\nAnswer: grep string filename<\/p>\n
How do you search for a string inside a directory? <\/b>
\nAnswer: grep string *<\/p>\n
How do you search for a string in a directory with the subdirectories recursed? <\/b>
\nAnswer: grep -r string *<\/p>\n
What are PIDs? <\/b>
\nAnswer: They are process IDs given to processes. A PID can vary from 0 to 65535.<\/p>\n
How do you list currently running process? <\/b>
\nAnswer: ps<\/p>\n
How do you stop a process? <\/b>
\nAnswer: kill pid<\/p>\n
How do you find out about all running processes? <\/b>
\nAnswer: ps -ag<\/p>\n
How do you stop all the processes, except the shell window? <\/b>
\nAnswer: kill 0<\/p>\n
How do you fire a process in the background? <\/b>
\nAnswer: .\/process-name &<\/p>\n
How do you refer to the arguments passed to a shell script? <\/b>
\nAnswer: $1, $2 and so on. $0 is your script name.<\/p>\n
What\u2019s the conditional statement in shell scripting? <\/b>
\nAnswer: if {condition} then \u2026 fi<\/p>\n
How do you do number comparison in shell scripts? <\/b>
\nAnswer: -eq, -ne, -lt, -le, -gt, -ge<\/p>\n
How do you test for file properties in shell scripts? <\/b>
\nAnswer: -s filename tells you if the file is not empty, -f filename tells you whether the argument is a file, and not a directory, -d filename tests if the argument is a directory, and not a file, -w filename tests for writeability, -r filename tests for readability, -x filename tests for executability<\/p>\n
How do you do Boolean logic operators in shell scripting? <\/b>
\nAnswer: ! tests for logical not, -a tests for logical and, and -o tests for logical or.<\/p>\n
How do you find out the number of arguments passed to the shell script? <\/b>
\nAnswer: $#<\/p>\n
What\u2019s a way to do multilevel if-else\u2019s in shell scripting? <\/b>
\nAnswer: if {condition} then {statement} elif {condition} {statement} fi<\/p>\n
How do you write a for loop in shell? <\/b>
\nAnswer: for {variable name} in {list} do {statement} done<\/p>\n
How do you write a while loop in shell? <\/b>
\nAnswer: while {condition} do {statement} done<\/p>\n
How does a case statement look in shell scripts? <\/b>
\nAnswer: case {variable} in {possible-value-1}) {statement};; {possible-value-2}) {statement};; esac<\/p>\n
How do you read keyboard input in shell scripts? <\/b>
\nAnswer: read {variable-name}<\/p>\n
How do you define a function in a shell script? <\/b>
\nAnswer: function-name() { #some code here return }<\/p>\n
How does getopts command work? <\/b>
\nAnswer: The parameters to your script can be passed as -n 15 -x 20. Inside the script, you can iterate through the getopts array as while getopts n:x option, and the variable $option contains the value of the entered option.<\/p>\n
What\u2019s a way to do multilevel if-else\u2019s in shell scripting?<\/b>
\nAnswer: if then elif fi<\/p>\n
How do you write a for loop in shell? <\/b>
\nAnswer: for in do done<\/p>\n
How do you write a while loop in shell?<\/b>
\nAnswer: while do done<\/p>\n
How does a case statement look in shell scripts? <\/b>
\nAnswer: case in ) ;; ) ;; esac<\/p>\n
How do you define a function in a shell script?<\/b>
\nAnswer: function-name()<\/p>\n
How do you find out about all running processes?<\/b>
\nAnswer: ps -ag<\/p>\n
How do you stop a process? <\/b>
\nAnswer: kill pid<\/p>\n
How do you remove a file?<\/b>
\nAnswer: rm<\/p>\n
How do you remove recursively?<\/b>
\nAnswer: rm -rf<\/p>\n
What are PIDs?<\/b>
\nAnswer: They are process IDs given to processes. A PID can vary…<\/p>\n
How do you list currently running process?<\/b>
\nAnswer: ps<\/p>\n
What is $$?<\/b><\/p>\n
What is a named pipe?<\/p>\n
What does || mean?<\/p>\n
What does && mean?<\/p>\n
What is a loop?<\/p>\n
What does while do?<\/p>\n
What is a function?<\/p>\n
What are the different kinds of loops available in shell script?<\/b>
\nfor if while case<\/p>\n
What does $# stand for?<\/b><\/p>\n
$# returns the number of parameters that are passed to a shell script
\n$? returns the exit code of the last executed command (0 : Successful, 1 or other: Failed)<\/p>\n
What does $? return?<\/b>
\nWill return the status of the command which is executed lastly.
\n0 > Success
\n2 > Error<\/p>\n
How do u open a read only file in Unix?<\/b>
\n“vi -R filename”<\/p>\n
What is the difference between a shell variable that is exported and the one that is not exported? <\/b><\/p>\n
If you have a string “one two three”, Which shell command would you use to extract the strings?<\/b><\/p>\n
How do you schedule a command to run at 4:00 every morning?<\/b><\/p>\n
How will you list only the empty lines in a file (using grep)? <\/b>
\ngrep ^$ filename.txt<\/p>\n
When you login to a c shell, which script would be run first? (before the terminal is ready for the user) <\/b><\/p>\n
first \/etc\/.login script is run & after that
\n~\/.login is run & then ~\/.cshrc is run.<\/p>\n
How would you get the character positions 10-20 from a text file? <\/b>
\ncat filename.txt | cut -c 10-20<\/p>\n
How would you print just the 25th line in a file (smallest possible script please)?<\/b>
\ntail -n +25\u00c2 | head -1 OR
\nhead -n 25 | tail -1<\/p>\n
How would you replace the n character in a file with some xyz?<\/b>
\nsed ‘s\/n\/xyz\/g’ filename > new_filename<\/p>\n
Grep | SED |<\/p>\n
How you will list the ordinary files in your current directory that are not user-writable?<\/p>\n
Use Command substitution with grep to list the names of the persons from emp.lst who were born today.<\/p>\n
How will you remove blank lines from a file using (i) grep\u00a0 and (ii) sed?<\/p>\n
Locate lines longer than 100 abd smaller than 150 characters using (i) grep\u00a0 and (ii) sed?<\/p>\n
How do you delete all leading and trailing spaces in all lines of a file?<\/p>\n
Making Script Interactive<\/strong> Special Parameters Used by Shell<\/strong> Exit status of command<\/strong> 0 indicates the success and other values point to failure<\/p>\n The Logical Operator && and ||<\/strong> Usage of \u2013a and -o<\/p>\n The if Conditional If command is successful If command is successful Using test AND [ ] to evaluate expressions<\/strong> Numeric Comparison Operators used by test<\/strong> String Tests used by test<\/strong><\/p>\n File related Tests with test The case CONDITIONAL<\/strong> *)\u00a0\u00a0 echo \u201cInvalid options\u201d for<\/strong> for file in *.htm *.html while<\/strong><\/p>\n while consition is true basename \u2013 Changing Filename Extension<\/strong> set \u00a0AND shift \u2013 Manupulating the Positional Parameters<\/strong> # set `date` Note- set parses its arguments on the delimiters specified in the environment variable IFS which by default is whitespace.<\/p>\n Shift \u2013 Shifting arguments left<\/strong><\/p>\n Maximum number of Bash arguments<\/strong>
\n# read name
\n# echo \u201c$name\u201d<\/p>\n
\n# $* – It stores the complete set of positional parameters as a single string
\n# $? \u2013 Exit Status of last command
\n# $# – Number of arguments specified in command line
\n# $0 \u2013 Holds the command name itself
\n# $$ – PID of current Shell
\n# $! \u2013 PID of last the last Background job<\/p>\n
\n# exit 0 \u2013 Used when everything went fine
\n# exit 1 \u2013 Used when something went wrong<\/p>\n
\ncmd1 && cmd2 – cmd2 is excuted only when cmd1 succeeds.
\ncmd1 || cmd2 – cmd2 is excuted only when cmd1 Fails<\/p>\n
\nIf command is successful
\nthen
\nexecute command
\nelse
\nexecute command
\nfi<\/p>\n
\nthen
\nexecute command
\nfi<\/p>\n
\nthen
\nexecute command
\nelif command is successful
\nthen
\nexecute command
\nelse
\nexecute command
\nfi<\/p>\n
\n# test $x \u2013eq $y
\n# [$x \u2013eq $y]<\/p>\n
\n# -eq \u2013 Equal to
\n# -ne \u2013 Not Equal to
\n# -gt \u2013 Greater than
\n# -ge \u2013 Greater than or equal to
\n# -ge \u2013 Less than
\n# -le \u2013 Less than or equal to<\/p>\n\n\n
\n Test<\/strong><\/td>\n True if<\/strong><\/td>\n<\/tr>\n \n s1=s2<\/strong><\/td>\n String s1 = s2<\/td>\n<\/tr>\n \n s1 != s2<\/strong><\/td>\n String s1 is not equal to s2<\/td>\n<\/tr>\n \n -n stg<\/strong><\/td>\n String stg is not a null string<\/td>\n<\/tr>\n \n -z stg<\/strong><\/td>\n String stg is a null string<\/td>\n<\/tr>\n \n stg<\/strong><\/td>\n String stg is assigned and not null<\/td>\n<\/tr>\n \n s1 == s2<\/strong><\/td>\n String s1 =s2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n<\/strong><\/p>\n\n\n
\n Test<\/strong><\/td>\n True if<\/strong><\/td>\n<\/tr>\n \n -f file<\/strong><\/td>\n file exists and is a regular file<\/td>\n<\/tr>\n \n -r file<\/strong><\/td>\n file exists and is a readable<\/td>\n<\/tr>\n \n -w file<\/strong><\/td>\n file exists and is a writeable<\/td>\n<\/tr>\n \n -x file<\/strong><\/td>\n file exists and is a executable<\/td>\n<\/tr>\n \n -d file<\/strong><\/td>\n file exists and is a dirctory<\/td>\n<\/tr>\n \n -s file<\/strong><\/td>\n file exists and has a size greate than ero<\/td>\n<\/tr>\n \n -e file<\/strong><\/td>\n file exists<\/td>\n<\/tr>\n \n -u file<\/strong><\/td>\n file exists and has\u00a0 SUID bit set<\/td>\n<\/tr>\n \n -L file<\/strong><\/td>\n file exists and is a Symbolic link<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nread choice
\ncase \u201c$choice\u201d in<\/p>\n\n
\nesac<\/p>\n
\nfor variable in list
\ndo
\ncommands
\ndone<\/p>\n
\ndo
\nsed \u2018s\/strong\/STONG\/g\u2019 $file >> $$
\nmv $$ $file
\ngzip $file
\ndone<\/p>\n
\ndo
\ncommands
\ndone<\/p>\n
\n# basename \/home\/henry\/project3\/dec2bin.pl
\n#dec2bin.pl
\n# basename ux2nd.txt txt
\n# ux2nd.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 – txt stripped off<\/p>\n
\n# set 9876 2345 6213
\n# echo \u201c\\$1 is $1, \\$2 is $2, \\$3 is $3\u201d
\n# $1 is 9876, $2 is 2346, $3 is 6213<\/p>\n
\n# echo $*<\/p>\n
\nOn a 32-bit Linux, this is ARGMAX\/4-1 (32767). This becomes relevant if the average length of arguments is smaller than 4.
\nLinux 2.6.23, one argument must not be longer than MAX_ARG_STRLEN (131072).<\/p>\n