5.4shell Programming 3

5.4

Exercise: Write a script

Determine if there is a user's default shell for bash on the current system;

If so, the number of such users is displayed, otherwise, no such user is shown

Nano dd.sh

#!/bin/bash

#

grep "\<bash$"/etc/passwd &>/dev/null

RETVAL = $?

If [$RETVAL-eq 0];then

USERS = ' grep ' \<bash$ '/etc/passwd | Wc-l '

echo "The shells of $USERS USERS is bash."

Else

echo "No such user."

Fi

Exercise: Write a script

Determine if a user's default shell is bash on the current system

If so, displays one of the user names, otherwise, it shows no such user

Nano dd.sh

#!/bin/bash

#

grep "\<bash$"/etc/passwd &>/dev/null

RETVAL = $?

If [$RETVAL-eq 0];then

USERS = ' grep ' \<bash$ '/etc/passwd | head-1 | cut-d:-f1 '

echo "$USERS is one of such USERS"

Else

echo "No such user."

Fi

Exercise: Write a script

Given a file, such as/etc/inittab

Determine if there is a blank line in this file

If so, displays the number of blank lines, otherwise, no blank lines are displayed

#!/bin/bash

FILE =/etc/inittab

If grep "^$" $FILE &>/dev/null;then

echo "Total Blank lines: ' grep" ^$ "$FILE | Wc-l '. "

Else

echo "No blank line."

Fi

Exercise: Write a script

Given a user, determine if its UID and GID are the same

If it does, the user is displayed as "good guy";

#! /bin/bash

USERNAME =user1

USERID = ' Id-u $USERNAME '

GROUPID = ' Id-g $USERNAME '

if[$USERID-eq $GROUPID];then

echo "Good guy"

Else

echo "Bad guy"

Fi

Further requirements: Do not use the ID command to obtain its ID number

Exercise: Writing a script

Given a user, get their password warning period:

And then determine whether the last time the user changed the password is today less than the warning period

Hint: The method of arithmetic operation $[$A-$B]: The result of the value of variable A minus the value of variable B

If it is less than, "Warning" is displayed: otherwise, "OK" is displayed

Exercise: Write a script

The total entry of the history command in the Interpretation command history is greater than 1000;

"Some command would gone."; Otherwise, "OK" is displayed

How to perform arithmetic operations in the shell:

A = 3

B = 6

1 Let arithmetic op-expression

Let C = $A + $B

2 $[arithmetic operation expression]

c = $[$A + $B]

3 $ ((arithmetic expression))

c = $ (($A + $B))

4 The Expr command operation expression, with spaces between the operands and operators in the expression, and

Using a command reference

c = ' expr $A + $B '

5.4shell Programming 3