Common Unix General Interview Preparation Guide

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>wc -l filename

Example:cat>file
1 abc 100
2 def 200
3 ghi 300
4 ijk 500

>wc -l file
4 file

Use extended grep command

egrep 'searchstr1 | searchchstr2' file.txt

Hidden files will start a period (.) in their names. To
list them use -a option of ls command.

like, ls -ltra

nslookup <host_name>
e.g: nslookup ibm6

ls -ald (In solaris)

ls - ltra (In unix)

parateter card is a type of card used to provide voice
digital communication to radio stations for therir FMs

V1: less secure ,
lacks a strong mechanism for ensuring the
integrity of the connection.
if machine name user ogged in from is present in one of the
follwing file then connection is established.
$HOME/.rhosts, $HOME/.shosts, /etc/hosts.equiv, or
/etc/shosts.equiv,
V2:More secure
provides additional mechanisms for confidential-
ity

cat command:used to create and displaying the information
present in the files.
Syntax for file creation: cat>(filename)
Syntax for displaying information in those file: cat
(filename)
Syntax for Appending data in that files: cat>>(filename)
ls command: to list the files present in the system.
ls :will list all the files present in that directory.
ls -l:for long listing of the files.
ls -a:to view hidden files.
ls -ld:to get the permission for the current directory.
ls -ltr:to get the latest file in the directory.
man command:to know more information about the cmds.
Syntax:man <cmd>
eg:man ls
touch: is also used to create the multiple empty files at a
time.
Syntax:touch f{1..10}:creates 10 empty files with names
f1,...f10.
pwd:is used to know present working directory.
cd f1 :to changed to the directory f1.
mkdir <direcoty name>:to create new directory.
rmdir <directory name>:to remove directory when it is empty
only.
rm <filename>:to remove the files.
rm -r <direcotry name>:to remove the files in that
directory recursively.
rm -f <directoryname>:to remove the files in that directory
forcebily.
cp <source> <destination>: to copy the contents of one file
to another
cp -rR <s> <d>:will copy the contents of one directory to
another.
mv <s> <d>:will move the contents of one file to another.
ls -l|grep ^d:toget the list of directories.
ls -i|grep ^_:to get the list of files.
clear-used to clear the screen

grep 'word1|word2' <filename>

nfsv3 acces through udp protocol whereas nfsv4 acces through
TCP/IP protocol

find /tmp -mtime n where n can be +ve or -ve

+n says, file modified in last n days
-n says, file modified more than n days ago

ex. if today is 5th of a month

file1 has mtime 3rd
file2 has mtime 2nd

then find . -mtime 2 will report file1
then find . -mtime -2 will report file2 only

Suppose they are asking for displaying just one of the
columns in a directory, make a note of that column number
as it appears when we do a ls -lrt. Then we can use awk to
just display the one columns as o/p.

If column number is n, then do this:

ls -lrt | awk '{print $n}'

grep stands as Globally Search for Regular Expression
and Print.
It is used for displaying the pattern matching lines from
requested file or files .

./test.pl&
jobs -- get job id of the above process
[3] Running ./test.pl &
fg 3

diff file1 file2

Above command will display all the lines which r diff in
file1 & file2 whereas, cmp will only display 1st occurance
of difference.

df -h----- it shows the space alocation for oracle dsata file.
olny for space alocation execute command ll -lrth.

use ps command "process status". I will use "ps -ef" to
list every process in detail.

sed -n '/matchingpattern/g' file1 file2...