Standard I/O redirection operator

Keyboard----------standard Input operator

Monitor---------standard outpout operator

Monitor--------error showing output

• > = greater than , overwrite the standard output
• >> = Append the standard output
• 2> = Overwrite error output
• 2>> = Append error output
• &> = complete results for etc. error & output is a redirect
• Tr = translate command

Etc. tr ‘a-z’ ‘A-Z’ < file name

Cal > file

Cal >a

Cal 04 04 >> file ---showing calendar in file

Ping -c 4 192.168.0.254 >a ---print a ping statement in a file 4 time only

• Find /etc –name passwd
• Find /etc –name passwd 2>a
• Find /etc –name passwd >a
• Find /etc –name passwd & >a

Note: find command used to search a error & non-error files.

# User , group & permission Topic

UID = stands for user identification number

GID= stands for group identification number

/etc/passwd ----store user information

/etc/group ------store group information

/etc/shadow ----store user password

/etc/gpasswd---store group passwd.

Create a user with a command ,

Useradd harry (create a new user)

Passwd harry (to assign passwd to harry user)

Note: we also can use “ adduser “ command to add a new user

• System-config-users = to create a user with graphical mode
• Vim /etc/paaswd

Username:passwd(x):uid:gid: : /home:/bin/bash

Note:- in /etc/passwd there are 7 field

• /etc/group = to check users group from here

There are two methods of permission

• Symbolic method & Numerical method