diff --git a/codes/shell/array-demo.sh b/codes/shell/array-demo.sh
new file mode 100644
index 0000000..65ff2ef
--- /dev/null
+++ b/codes/shell/array-demo.sh
@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+
+# 创建数组
+nums=([2]=2 [0]=0 [1]=1)
+colors=(red yellow "dark blue")
+
+# 访问数组的单个元素
+echo ${nums[1]}
+# Output: 1
+
+# 访问数组的所有元素
+echo ${colors[*]}
+# Output: red yellow dark blue
+
+echo ${colors[@]}
+# Output: red yellow dark blue
+
+printf "+ %s\n" ${colors[*]}
+# Output:
+# + red
+# + yellow
+# + dark
+# + blue
+
+printf "+ %s\n" "${colors[*]}"
+# Output:
+# + red yellow dark blue
+
+printf "+ %s\n" "${colors[@]}"
+# Output:
+# + red
+# + yellow
+# + dark blue
+
+# 访问数组的部分元素
+echo ${nums[@]:0:2}
+# Output:
+# 0 1
+
+# 访问数组长度
+echo ${#nums[*]}
+# Output:
+# 3
+
+# 向数组中添加元素
+colors=(white "${colors[@]}" green black)
+echo ${colors[@]}
+# Output:
+# white red yellow dark blue green black
+
+# 从数组中删除元素
+unset nums[0]
+echo ${nums[@]}
+# Output:
+# 1 2
diff --git a/codes/shell/array/arrayDemo.sh b/codes/shell/array/arrayDemo.sh
deleted file mode 100644
index b493c65..0000000
--- a/codes/shell/array/arrayDemo.sh
+++ /dev/null
@@ -1,71 +0,0 @@
-#!/usr/bin/env bash
-
-# 声明数组
-## 声明数组方式一
-animals[0]=Cat
-animals[1]=Dog
-animals[2]=Fish
-## 声明数组方式二
-colors=(Red Green Blue)
-
-
-# 根据下标获取数组中的元素
-echo "=========== 根据下标获取数组中的元素 ==========="
-echo "\${colors[1]} : " ${colors[1]}
-# 输出：
-# ${colors[1]} :  Green
-
-
-# 数组切片
-echo "=========== 数组切片 ==========="
-colors[1]="Dark Green"
-
-echo "\${colors[*]} : "
-printf "+ %s\n" ${colors[*]}
-# 输出：
-# + Red
-# + Dark
-# + Green
-# + Blue
-
-echo "\"\${colors[*]}\" : "
-printf "+ %s\n" "${colors[*]}"
-# 输出：
-# + Red Dark Green Blue
-
-echo "\"\${colors[@]}\" : "
-printf "+ %s\n" "${colors[@]}"
-# 输出：
-# + Red
-# + Dark
-# + Green
-# + Blue
-
-echo "\"\${colors[@]:0:2}\" : " ${colors[@]:0:2} ### Red Dark Green
-
-# 向数组中添加元素
-echo "=========== 向数组中添加元素 ==========="
-colors=(Yellow "${colors[@]}" Pink Black)
-echo "\"\${colors[@]}\" : " ${colors[@]}
-# 输出：
-# Yellow Red Dark Green Blue Pink Black
-
-# 向数组中删除元素
-echo "=========== 向数组中删除元素 ==========="
-unset colors[0]
-echo "\"\${colors[@]}\" : " ${colors[@]}
-# 输出：
-# Red Dark Green Blue Pink Black
-
-# 获取数组的长度
-echo "=========== 获取数组的长度 ==========="
-## 获取数组的长度方式一
-echo "\${#colors[*]} : ${#colors[*]}"
-## 获取数组的长度方式二
-echo "\${#colors[@]} : ${#colors[@]}"
-
-
-for (( i = 0; i < animals; i ++ )); do
-  echo $i
-done
-
diff --git a/codes/shell/comment-demo.sh b/codes/shell/comment-demo.sh
new file mode 100644
index 0000000..0a5e421
--- /dev/null
+++ b/codes/shell/comment-demo.sh
@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+#--------------------------------------------
+# shell 注释示例
+# author：zp
+#--------------------------------------------
+
+# echo '这是单行注释'
+
+########## 这是分割线 ##########
+
+:<<EOF
+echo '这是多行注释'
+echo '这是多行注释'
+echo '这是多行注释'
+EOF
+
+# Execute: ./comment-demo.sh
+# Output: null
diff --git a/codes/shell/operator/operator-demo.sh b/codes/shell/operator/operator-demo.sh
new file mode 100644
index 0000000..0baa1eb
--- /dev/null
+++ b/codes/shell/operator/operator-demo.sh
@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+
+x=10
+if [[ -n $1 ]]; then
+  x=$1
+fi
+
+y=20
+if [[ -n $2 ]]; then
+  y=$2
+fi
+
+echo "x=${x}, y=${y}"
+
+val=`expr ${x} + ${y}`
+echo "${x} + ${y} = $val"
+
+val=`expr ${x} - ${y}`
+echo "${x} - ${y} = $val"
+
+val=`expr ${x} \* ${y}`
+echo "${x} * ${y} = $val"
+
+val=`expr ${y} / ${x}`
+echo "${y} / ${x} = $val"
+
+val=`expr ${y} % ${x}`
+echo "${y} % ${x} = $val"
+
+if [[ ${x} == ${y} ]]; then
+  echo "${x} = ${y}"
+fi
+if [[ ${x} != ${y} ]]; then
+  echo "${x} != ${y}"
+fi
+
+#  Execute: ./operator-demo.sh
+#  Output:
+#  x=10, y=20
+#  10 + 20 = 30
+#  10 - 20 = -10
+#  10 * 20 = 200
+#  20 / 10 = 2
+#  20 % 10 = 0
+#  10 != 20
+
+#  Execute: ./operator-demo.sh 10 30
+#  Output:
+#  x=10, y=30
+#  10 + 30 = 40
+#  10 - 30 = -20
+#  10 * 30 = 300
+#  30 / 10 = 3
+#  30 % 10 = 0
+#  10 不等于 30
diff --git a/codes/shell/operator/operator-demo2.sh b/codes/shell/operator/operator-demo2.sh
new file mode 100644
index 0000000..05cd0b2
--- /dev/null
+++ b/codes/shell/operator/operator-demo2.sh
@@ -0,0 +1,59 @@
+#!/usr/bin/env bash
+
+x=10
+if [[ -n $1 ]]; then
+  x=$1
+fi
+
+y=20
+if [[ -n $2 ]]; then
+  y=$2
+fi
+
+echo "x=${x}, y=${y}"
+
+if [[ ${x} -eq ${y} ]];then
+   echo "${x} -eq ${y} : x 等于 y"
+else
+   echo "${x} -eq ${y}: x 不等于 y"
+fi
+
+if [[ ${x} -ne ${y} ]]; then
+   echo "${x} -ne ${y}: x 不等于 y"
+else
+   echo "${x} -ne ${y}: x 等于 y"
+fi
+
+if [[ ${x} -gt ${y} ]]; then
+   echo "${x} -gt ${y}: x 大于 y"
+else
+   echo "${x} -gt ${y}: x 不大于 y"
+fi
+
+if [[ ${x} -lt ${y} ]]; then
+   echo "${x} -lt ${y}: x 小于 y"
+else
+   echo "${x} -lt ${y}: x 不小于 y"
+fi
+
+if [[ ${x} -ge ${y} ]]; then
+   echo "${x} -ge ${y}: x 大于或等于 y"
+else
+   echo "${x} -ge ${y}: x 小于 y"
+fi
+
+if [[ ${x} -le ${y} ]]; then
+   echo "${x} -le ${y}: x 小于或等于 y"
+else
+   echo "${x} -le ${y}: x 大于 y"
+fi
+
+#  Execute: ./operator-demo2.sh
+#  Output:
+#  x=10, y=20
+#  10 -eq 20: x 不等于 y
+#  10 -ne 20: x 不等于 y
+#  10 -gt 20: x 不大于 y
+#  10 -lt 20: x 小于 y
+#  10 -ge 20: x 小于 y
+#  10 -le 20: x 小于或等于 y
diff --git a/codes/shell/operator/operator-demo3.sh b/codes/shell/operator/operator-demo3.sh
new file mode 100644
index 0000000..68dc499
--- /dev/null
+++ b/codes/shell/operator/operator-demo3.sh
@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+
+x=10
+if [[ -n $1 ]]; then
+  x=$1
+fi
+
+y=20
+if [[ -n $2 ]]; then
+  y=$2
+fi
+
+echo "x=${x}, y=${y}"
+
+if [[ ${x} != ${y} ]];then
+   echo "${x} != ${y} : x 不等于 y"
+else
+   echo "${x} != ${y}: x 等于 y"
+fi
+
+if [[ ${x} -lt 100 && ${y} -gt 15 ]];then
+   echo "${x} 小于 100 且 ${y} 大于 15 : 返回 true"
+else
+   echo "${x} 小于 100 且 ${y} 大于 15 : 返回 false"
+fi
+
+if [[ ${x} -lt 100 || ${y} -gt 100 ]];then
+   echo "${x} 小于 100 或 ${y} 大于 100 : 返回 true"
+else
+   echo "${x} 小于 100 或 ${y} 大于 100 : 返回 false"
+fi
+
+if [[ ${x} -lt 5 || ${y} -gt 100 ]];then
+   echo "${x} 小于 5 或 ${y} 大于 100 : 返回 true"
+else
+   echo "${x} 小于 5 或 ${y} 大于 100 : 返回 false"
+fi
+
+#  Execute: ./operator-demo3.sh
+#  Output:
+#  x=10, y=20
+#  10 != 20 : x 不等于 y
+#  10 小于 100 且 20 大于 15 : 返回 true
+#  10 小于 100 或 20 大于 100 : 返回 true
+#  10 小于 5 或 20 大于 100 : 返回 false
diff --git a/codes/shell/operator/operator-demo4.sh b/codes/shell/operator/operator-demo4.sh
new file mode 100644
index 0000000..753daae
--- /dev/null
+++ b/codes/shell/operator/operator-demo4.sh
@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+
+x=10
+if [[ -n $1 ]]; then
+  x=$1
+fi
+
+y=20
+if [[ -n $2 ]]; then
+  y=$2
+fi
+
+echo "x=${x}, y=${y}"
+
+if [[ ${x} -lt 100 && ${y} -gt 100 ]]
+then
+   echo "${x} -lt 100 && ${y} -gt 100 返回 true"
+else
+   echo "${x} -lt 100 && ${y} -gt 100 返回 false"
+fi
+
+if [[ ${x} -lt 100 || ${y} -gt 100 ]]
+then
+   echo "${x} -lt 100 || ${y} -gt 100 返回 true"
+else
+   echo "${x} -lt 100 || ${y} -gt 100 返回 false"
+fi
+
+#  Execute: ./operator-demo4.sh
+#  Output:
+#  x=10, y=20
+#  10 -lt 100 && 20 -gt 100 返回 false
+#  10 -lt 100 || 20 -gt 100 返回 true
diff --git a/codes/shell/operator/operator-demo5.sh b/codes/shell/operator/operator-demo5.sh
new file mode 100644
index 0000000..828803c
--- /dev/null
+++ b/codes/shell/operator/operator-demo5.sh
@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+
+x="abc"
+if [[ -n $1 ]]; then
+  x=$1
+fi
+
+y="xyz"
+if [[ -n $2 ]]; then
+  y=$2
+fi
+
+echo "x=${x}, y=${y}"
+
+if [[ ${x} = ${y} ]];then
+   echo "${x} = ${y} : x 等于 y"
+else
+   echo "${x} = ${y}: x 不等于 y"
+fi
+
+if [[ ${x} != ${y} ]];then
+   echo "${x} != ${y} : x 不等于 y"
+else
+   echo "${x} != ${y}: x 等于 y"
+fi
+
+if [[ -z ${x} ]];then
+   echo "-z ${x} : 字符串长度为 0"
+else
+   echo "-z ${x} : 字符串长度不为 0"
+fi
+
+if [[ -n "${x}" ]];then
+   echo "-n ${x} : 字符串长度不为 0"
+else
+   echo "-n ${x} : 字符串长度为 0"
+fi
+
+if [[ ${x} ]];then
+   echo "${x} : 字符串不为空"
+else
+   echo "${x} : 字符串为空"
+fi
+
+#  Execute: ./operator-demo5.sh
+#  Output:
+#  x=abc, y=xyz
+#  abc = xyz: x 不等于 y
+#  abc != xyz : x 不等于 y
+#  -z abc : 字符串长度不为 0
+#  -n abc : 字符串长度不为 0
+#  abc : 字符串不为空
diff --git a/codes/shell/operator/operator-demo6.sh b/codes/shell/operator/operator-demo6.sh
new file mode 100644
index 0000000..954d84e
--- /dev/null
+++ b/codes/shell/operator/operator-demo6.sh
@@ -0,0 +1,49 @@
+#!/usr/bin/env bash
+
+file="/etc/hosts"
+
+if [[ -r ${file} ]];then
+   echo "${file} 文件可读"
+else
+   echo "${file} 文件不可读"
+fi
+if [[ -w ${file} ]];then
+   echo "${file} 文件可写"
+else
+   echo "${file} 文件不可写"
+fi
+if [[ -x ${file} ]];then
+   echo "${file} 文件可执行"
+else
+   echo "${file} 文件不可执行"
+fi
+if [[ -f ${file} ]];then
+   echo "${file} 文件为普通文件"
+else
+   echo "${file} 文件为特殊文件"
+fi
+if [[ -d ${file} ]];then
+   echo "${file} 文件是个目录"
+else
+   echo "${file} 文件不是个目录"
+fi
+if [[ -s ${file} ]];then
+   echo "${file} 文件不为空"
+else
+   echo "${file} 文件为空"
+fi
+if [[ -e ${file} ]];then
+   echo "${file} 文件存在"
+else
+   echo "${file} 文件不存在"
+fi
+
+#  Execute: ./operator-demo6.sh
+#  Output:(根据文件的实际情况，输出结果可能不同)
+#  /etc/hosts 文件可读
+#  /etc/hosts 文件可写
+#  /etc/hosts 文件不可执行
+#  /etc/hosts 文件为普通文件
+#  /etc/hosts 文件不是个目录
+#  /etc/hosts 文件不为空
+#  /etc/hosts 文件存在
diff --git a/codes/shell/operator/operatorDemo.sh b/codes/shell/operator/operatorDemo.sh
deleted file mode 100644
index fbe0508..0000000
--- a/codes/shell/operator/operatorDemo.sh
+++ /dev/null
@@ -1,30 +0,0 @@
-#!/usr/bin/env bash
-
-a=10
-b=20
-
-echo "a=$a, b=$b"
-
-val=`expr $a + $b`
-echo "a + b : $val"
-
-val=`expr $a - $b`
-echo "a - b : $val"
-
-val=`expr $a \* $b`
-echo "a * b : $val"
-
-val=`expr $b / $a`
-echo "b / a : $val"
-
-val=`expr $b % $a`
-echo "b % a : $val"
-
-if [ $a == $b ]
-then
-  echo "a 等于 b"
-fi
-if [ $a != $b ]
-then
-  echo "a 不等于 b"
-fi
diff --git a/codes/shell/operator/operatorDemo02.sh b/codes/shell/operator/operatorDemo02.sh
deleted file mode 100644
index 640e6f3..0000000
--- a/codes/shell/operator/operatorDemo02.sh
+++ /dev/null
@@ -1,43 +0,0 @@
-#!/usr/bin/env bash
-
-a=10
-b=20
-
-echo "a=$a, b=$b"
-
-if [ $a -eq $b ]
-then
-  echo "$a -eq $b : a 等于 b"
-else
-  echo "$a -eq $b: a 不等于 b"
-fi
-if [ $a -ne $b ]
-then
-  echo "$a -ne $b: a 不等于 b"
-else
-  echo "$a -ne $b : a 等于 b"
-fi
-if [ $a -gt $b ]
-then
-  echo "$a -gt $b: a 大于 b"
-else
-  echo "$a -gt $b: a 不大于 b"
-fi
-if [ $a -lt $b ]
-then
-  echo "$a -lt $b: a 小于 b"
-else
-  echo "$a -lt $b: a 不小于 b"
-fi
-if [ $a -ge $b ]
-then
-  echo "$a -ge $b: a 大于或等于 b"
-else
-  echo "$a -ge $b: a 小于 b"
-fi
-if [ $a -le $b ]
-then
-  echo "$a -le $b: a 小于或等于 b"
-else
-  echo "$a -le $b: a 大于 b"
-fi
diff --git a/codes/shell/string-demo.sh b/codes/shell/string-demo.sh
new file mode 100644
index 0000000..26bd6ae
--- /dev/null
+++ b/codes/shell/string-demo.sh
@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+
+################### 单引号和双引号 ###################
+################### 拼接字符串 ###################
+# 使用单引号拼接
+name1='white'
+str1='hello, '${name1}''
+str2='hello, ${name1}'
+echo ${str1}_${str2}
+# Output:
+# hello, white_hello, ${name1}
+
+# 使用双引号拼接
+name2="black"
+str3="hello, "${name2}""
+str4="hello, ${name2}"
+echo ${str3}_${str4}
+# Output:
+# hello, black_hello, black
+
+################### 获取字符串长度 ###################
+text="12345"
+echo ${#text}
+# Output:
+# 5
+
+################### 获取字符串长度 ###################
+text="12345"
+echo ${text:2:2}
+# Output:
+# 34
+
+################### 查找子字符串 ###################
+text="hello"
+echo `expr index "${text}" ll`
+# Output:
+# 3
diff --git a/codes/shell/variable-demo.sh b/codes/shell/variable-demo.sh
new file mode 100644
index 0000000..c7acaa1
--- /dev/null
+++ b/codes/shell/variable-demo.sh
@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+################### 声明变量 ###################
+word="hello"
+echo ${word}
+# Output: hello
+
+################### 只读变量 ###################
+rword="hello"
+echo ${rword}
+# Output: hello
+readonly rword
+# rword="bye"  # 如果放开注释，执行时会报错
+
+################### 删除变量 ###################
+dword="hello"  # 声明变量
+echo ${dword}  # 输出变量值
+# Output: hello
+
+unset dword    # 删除变量
+echo ${dword}
+# Output: （空）
diff --git a/codes/shell/variable/positionalVariableDemo.sh b/codes/shell/variable/positionalVariableDemo.sh
deleted file mode 100644
index 41a0b68..0000000
--- a/codes/shell/variable/positionalVariableDemo.sh
+++ /dev/null
@@ -1,18 +0,0 @@
-#!/usr/bin/env bash
-
-### 如果变量为空，赋给他们默认值
-: ${VAR:='default'}
-: ${1:='first'}
-echo "\$1 : " $1
-: ${2:='second'}
-echo "\$2 : " $2
-
-### 或者
-FOO=${FOO:-'default'}
-echo "FOO : " ${FOO}
-
-# execute: ./positionalVariableDemo.sh big small
-# output:
-# $1 :  big
-# $2 :  small
-# FOO :  default
diff --git a/codes/shell/variable/variableDemo.sh b/codes/shell/variable/variableDemo.sh
deleted file mode 100644
index 6384e85..0000000
--- a/codes/shell/variable/variableDemo.sh
+++ /dev/null
@@ -1,8 +0,0 @@
-#!/usr/bin/env bash
-
-username="Zhang Peng" ### 声明变量
-echo ${username} ### 输出变量的值
-unset username ### 删除变量
-echo ${username} ### 输出为空
-
-export HELLO="Hello World" ### 输出环境变量