1.shell 脚本写出检测 /tmp/size.log 文件如果存在显示它的内容，不存在则创建一个文件将创建时间写入。
编写脚本：
#!/bin/bash
FILE="/tmp/size.log"
if [ -f "$FILE" ]; then
echo "文件存在，显示文件内容："
cat "$FILE"
else
echo "文件不存在，创建文件并写入创建时间。"
echo "创建时间：(date)" \> "FILE"
fi
执行脚本结果：
[root@localhost ~]# vim 1.sh
[root@localhost ~]# chmod +x 1.sh
[root@localhost ~]# ./1.sh
文件不存在，创建文件并写入创建时间。
2.写一个 shel1 脚本,实现批量添加 20个用户,用户名为user01-20,密码为user 后面跟5个随机字符。
编写脚本：
#!/bin/bash
USER_PREFIX="user"
USER_COUNT=20
for ((i=1; i<=USER_COUNT; i++)); do
USERNAME="{USER_PREFIX}(printf "%02d" $i)"
PASSWORD="user$(tr -dc 'a-zA-Z0-9' < /dev/urandom | head -c 5)"
sudo useradd $USERNAME
echo -e "PASSWORD\\nPASSWORD" | sudo passwd $USERNAME
echo "用户 USERNAME 添加成功，密码为：PASSWORD"
done
执行脚本结果：
Changing password for user user01.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user01 添加成功，密码为：useraPHte
Changing password for user user02.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user02 添加成功，密码为：userclBkI
Changing password for user user03.
New password: Retype new password: passwd: all authentication tokens updated successfully.
用户 user03 添加成功，密码为：user5B8Yg
Changing password for user user04.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user04 添加成功，密码为：userCZmXl
Changing password for user user05.
New password: BAD PASSWORD: The password contains the user name in some form
Retype new password: passwd: all authentication tokens updated successfully.
用户 user05 添加成功，密码为：user0k5xR
Changing password for user user06.
New password: Retype new password: passwd: all authentication tokens updated successfully.
用户 user06 添加成功，密码为：userGaAG1
Changing password for user user07.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user07 添加成功，密码为：userZefFN
Changing password for user user08.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user08 添加成功，密码为：userord6b
Changing password for user user09.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user09 添加成功，密码为：userLitYu
Changing password for user user10.
New password: Retype new password: passwd: all authentication tokens updated successfully.
用户 user10 添加成功，密码为：userj37Vx
Changing password for user user11.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user11 添加成功，密码为：userv23j9
Changing password for user user12.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user12 添加成功，密码为：useruKikd
Changing password for user user13.
New password: Retype new password: passwd: all authentication tokens updated successfully.
用户 user13 添加成功，密码为：userxH9hs
Changing password for user user14.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user14 添加成功，密码为：userQyMIF
Changing password for user user15.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user15 添加成功，密码为：userMSIyp
Changing password for user user16.
New password: BAD PASSWORD: The password contains less than 3 character classes
Retype new password: passwd: all authentication tokens updated successfully.
用户 user16 添加成功，密码为：userJcDYt
Changing password for user user17.
New password: BAD PASSWORD: The password contains the user name in some form
Retype new password: passwd: all authentication tokens updated successfully.
用户 user17 添加成功，密码为：userh1Vsr
Changing password for user user18.
New password: Retype new password: passwd: all authentication tokens updated successfully.
用户 user18 添加成功，密码为：user7Zgho
Changing password for user user19.
New password: BAD PASSWORD: The password contains the user name in some form
Retype new password: passwd: all authentication tokens updated successfully.
用户 user19 添加成功，密码为：usery1vKl
Changing password for user user20.
New password: Retype new password: passwd: all authentication tokens updated successfully.
用户 user20 添加成功，密码为：userMeXQ3
3.编写个shel 脚本将/usr/local 日录下大于10M的文件转移到/tmp目录下
编写脚本：、
#!/bin/bash
SOURCE_DIR="/usr/local"
TARGET_DIR="/tmp"
if [ ! -d "$TARGET_DIR" ]; then
mkdir -p "$TARGET_DIR"
fi
find "SOURCE_DIR" -type f -size +10M -exec mv {} "TARGET_DIR" \;
echo "大于 10M 的文件已转移到 $TARGET_DIR"
执行脚本结果：
[root@localhost ~]# vim 3.sh
[root@localhost ~]# chmod +x 3.sh
[root@localhost ~]# ./3.sh
大于 10M 的文件已转移到 /tmp
以上为三个题目的解答！