Q What is Shell?
Ans: Shell is a command interpreter, which interprets the command which the user gives to the kernel. It can also be defined as an interface between a user and operating system.
Q How to debug the problems encountered in shell script/program?
Ans: Two options
1) Execute the script as “sh -x script.sh”
2) Put “set -x” in the script
Q Which is the symbol used for comments in bash shell scripting ?
Ans:
#
Q What is the difference between = and ==?
Ans:
= -> It is used for assigning value to the variable.
== -> It is used for string comparison.
Q How to get 4th element from each line of a file ?
Ans:
awk '{print $4}'Q What needs to be done before you can execute a shell script?
Ans:
You need to make the shell script executable using the chmod command.
This chmod command makes the shell script file “file1” executable for the user (owner) only:
$ chmod u+x file1
Below syntax makes it executable for all (everyone):
$ chmod a+x file1
Q How to pass argument to a script ?
Ans:
./script argument
Q How do you terminate an if statement?
Ans: Using “fi” . Check example below.
Q Give an example of if else statement
Ans:
#Testfile.sh script to test if the file exists#!/bin/kshcvfile=$1if [ -f $cvfile ]thenecho "$cvfile exists"else"$cvfile does not exists"fiexit 0
So you will execute the script as “./Testfile.sh file1” .
Q How to check if a directory exists?
Ans:
if [ -d $mydir ] thenecho "Directory exists"fi
Q How to calculate number of passed arguments ?
Ans:
$#
Q How to check if previous command run successful ?
Ans:
echo $?
If exit code is 0 it means command ran successfully
Q How to get last line from a file ?
Ans:
tail -1
Q How to redirect stdout and stderr streams to log.txt file from inside the script ?
Ans:
Add “exec >log.txt 2>&1” put this as the first command in the script
Q How to remove blank lines from a file?
Ans :
grep -v '^
Q Write a command to find all the files modified in less than 3 days and print the record count of each?
find . –mtime -3 –exec wc –l {} \;
Q How to find a process name from process ID?
ps -p PID
testcv.txt > testcv2.txt
Q Write a command to find all the files modified in less than 3 days and print the record count of each?
find . –mtime -3 –exec wc –l {} \;
Q How to find a process name from process ID?
ps -p PID