linux shell read command-Getting User Input Via Keyboard--re

ref：http://bash.cyberciti.biz/guide/Getting_User_Input_Via_Keyboard

You can accept input from the keyboard and assign an input value to a user defined shell variable using?.

Where,

• -p "Prompt"?: Display prompt to user without a newline.
• variable1?: The first input (word) is assigned to the variable1.
• variable2?: The second input (word) is assigned to the variable2.

Create a script called greet.sh as follows:

Save and close the file. Run it as follows:

Sample Outputs:

Enter your name?: Vivek Gite
Hi,Vivek Gite. Let us be friends!

Try the following examples.

A shell script to display the Internet domain name owner information (domain.sh):

You can time out read command using the -t option. It causes read to time out and return failure if a complete line of input is not read within TIMEOUT seconds. For example,if no input provided within 10 second,program will be aborted (domain2.sh):

The -s option causes input coming from a terminal do not be displayed on the screen. This is useful for password handling (readpass.sh):

Consider the following example:

Sample outputs:

Enter directory to delete?: foo bar /tmp/data
foo bar /tmp/data

The user supplied three values instead of one. The string is now made of three different fields. All three words are assigned to dirname using??internal field separator. The??determines how shell recognizes fields.

To display default value of?,enter:

You will see a whitespace which is nothing but a space,a tab,and a newline (default). You can print actual values of IFS using the following command (see?):

Sample outputs:

 ^I$
$

Where,

• $?- end of line i.e. newline
• ^I$?- tab and newline

Create a variable called nameservers and give it total 3 values as follows (note all values are separated by a whitespace):

Display the value of a variable nameservers with??or?:

OR

Now,you can simply split $nameservers using the??as follows (see?):

Where,

• The??reads input from $nameservers variable.
• The default value of??is used to assign values to three separate variables. Your input is broken into tokens using??and assigned to three variables.
• In other words,the??worked as token delimiter or separator.
• The first token (ns1.nixcraft.net) is saved as the value of the first variable ($ns1)
• The second token (ns2.nixcraft.net) is saved as the value of the second variable ($ns2).
• The third token (ns3.nixcraft.net) is saved as the value of the third variable ($ns3).
• To display the value of each variable use??or??as follows:

OR use the?

Sample outputs:

DNS Server #1 ns1.nixcraft.net
 #2 ns2.nixcraft.net
 #3 ns3.nixcraft.net

Consider the following??line:

gitevivek:x:1002:1002::/home/gitevivek:/bin/sh

Assign the above line to a variable called pwd:

Save the Internal Field Separator to a variable called old:

Set the Internal Field Separator to a colon (i.e. change the Internal Field Separator):

Read $pwd and generate tokens using $IFS and store them into respective fields:

Sample outputs:

Your login name is gitevivek,uid 1002,gid 1002,home dir set to /home/gitevivek with /bin/sh as login shell

Finally,restore the Internal Field Separator value using $old:

Where,

• :?- act as token separator on $pwd i.e. the contents of the IFS variable are used as token delimiters.

• login?- Field # 1 is generated using the first token and is saved as the value of the first variable ($login)
• password?- Field # 2 is generated using the second token and is saved as the value of the second variable ($password)
• uid?- Field # 3 and so on...
• gid?- Field # 4
• info?- Field # 5
• home?- Field # 6
• shell?- Field # 7

（编辑：李大同）

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