Shell Scripting Interview Questions

It gives exit status with echo command
Ex:- echo $?

It gives Zero when command is successfully executed otherwise it will gives garbage value.

$? returns the status of the last command executed . if the last command is successfull then it will 0 , otherwise it will retrun non-zero. ex: date ; echo $? or try this dte ; echo $?

There is a lot of shell available in UNIX.
Ex:- Bourne shell, Bash shell, CShell, Korn shell etc.

$cat /etc/shells <--from linux

cat cc | sed s/n/xyz/g

Also can be done with :g/n/s//xyz/g

awk NR==25

head -25 | nl | tail -1

Using vi editor. Read only files can be opened without any issues

Anything that opens a file, can open a read only file: cat, more, less, awk, pg, et all. The chmod command you put does not make a file read only, it makes it read/write for the user/owner.

i think by modifying the IFS, we can achieve this as follows, i hope this helps. #take for example there is an entry in /etc/password with this info santarvedi:x:500:500:santarvedi:/home/santarvedi:/...

perl -ane print "$F[0]"; < test.txt

You can use this I hope , replace the zero with the column number you want to print.Normally people use cut and awk command for extracting column.

sed /dd/d $file

sed s/dd //g file

Windows NT supports multitasking with the help of preemptive multitasking which is based on preemptive operating system. The operating system takes control of the processor from a task in two ways: W...

preemptive multitask

We can use either
head -2 file.dat | tail -1 or
cat file.dat | sed -n 2p > output.dat

sed -n 2p

Code
#!/bin/bash
total=0
c=0
for a in {1..3};
  do
        echo -n "Write a number : "
        read i
        if [ $i -ge 250 ] ; then let "c=c+1"
        fi
        let "total = i + total"
  done
echo "total = $total"
echo " > 250 = $c "

sed -n 25p file_name

cut -c 10-20 filename

ls -lrt | awk {priint "mv "$9" "%9".New"} | sh

Code
for i in *; 
do mv $i $i.New;
done

Positional parameters are reads either by displaying there value or can be assigned to another variables.

echo $1 $2 $9 ${10} ${20}
shift operators can be used to move around the positional parameters.

example: test.sh 1 2 3 4 5

a=$1

while [ -z "$a" ]
do

echo $a
shift

done

echo $1
echo $2

$# : Stands for counts of the number of the positional parameters passed to a script.

example test.sh 1 2 3 4 5 6 7 , there are 7 paramaters as passed so the count of the $# is 7

By using $# parameter, the program checks whether the right number of arguments have been entered.

grep "^$" filename

grep -c "^$" file name


here -c option count the no.of empty line..the anchors denotes the empty line from your file name

Current_time=`date +%H%M`
who -u | awk $Current_time - $4 <= 5 { print }

last -5|grep -i "logged in"|wc -l
last -5|grep -v "logged out"|wc -l

Code
mailx -s "<subject>" <email_id list> < <input_file>

The following is a more detailed example for using mailx in shell script. This should help.

Code
SUBJECT="Email Subject Line"
TO=xyz@company.com
CC=`tr '
' ', ' < mailCClist.txt`
#BCC="xyz2@comp.com"
 
echo "Send the E-mail message..."
/usr/bin/mailx -s "${SUBJECT}" ${TO} <<-END
 
~< ! uuencode $DCdir/$FileName "Result.txt"
 
~c ${CC}
~b ${BCC}
        Hi,
 
        Blah, Blah.. body of the email.
 
        Thanks
        Satya
        ~.
        END
 
echo "Mail Sent!!"
 

Code
uuencode attachment1 attachment1 | mailx -c x@yz.com,a@bc.com -s "subject" m@no.com 

You should be able to use something like the following example to get the CC option working with mailx. Preferably create a list of users needed to be put in the CC option (as mailCClist.txt in the ex...

in vi editor
vi connect.sh
#!/bin/bash

sqlplus -s sys as sysdba < startup
spool on;
spool ashu;
connect scott/tiger
select * from emp;
spool off;
exit;
EOF
cat ashu

sqlplus -s username/password@schema name
:wq

You can read the contents of file inside jar without extracting in shell script by using:

tar -tvf file.tar

jar tvf jarName.jar