Shell Loop statement: for

[root@master1-192,168117-18 ~] # vim users.txt

[root@master1-192,168117-18 ~] # vim Example.sh

#! / bin/bash

Read-p "Enter The Users Password:" PASSWD

For UNAME in cat users.txt

Do

Id $UNAME & > / dev/null

If [$?-eq 0]

Then echo "Already exits"

Else useradd $UNAME & > / dev/null

Echo "$PASSWD" | passwd-- stdin $UNAME & > / dev/null

If [$?-eq 0]

Then echo "$UNAME,create success!"

Else echo "$UNAME,Create failure!"

Fi

Fi

Done

[root@master1-192,168117-18 ~] # bash Example.sh

Enter The Users Password:1234

Zhangsan,create success!

Lisi,create success!

Wangmazi,create success!

Hanmeimei,create success!

Lilei,create success!

Bobo,create success!

Note: / dev/null is a file called Linux black hole. Redirecting output to this file is tantamount to deleting data (similar to trash bins without recycling), which keeps the user's screen window simple.

[root@master1-192,168117-18 ~] # vim ChechHosts.sh

#! / bin/bash

HLIST=$ (cat ~ / ipadds.txt) # $(executable command) = executable command

For IP in $HLIST

Do

Ping-c 3-I 0.2-W $IP & > / dev/null

If [$?-eq 0]; then

Echo "Host $IP is on-line."

Else

Echo "Host $IP is off-line."

Fi

Done