#!/bin/bash
#shell 流程控制语句
echo "====================if 语句===================="
if test $(ps -ef | grep -c "ssh") -gt 1
then
echo "true";
else
echo "false";
fi;
if [ $(ps -ef | grep -c "ssh") -gt 1 ]
then
echo "true";
else
echo "false";
fi
a=10
b=20
if [ $a == $b ];then
echo "a == b"
elif [[ $a -gt $b ]]; then
echo "a > b";
elif [ $a -lt $b ];then
echo "a < b";
else
echo "没有符合的条件"
fi
echo "====================for 语句===================="
for (( i = 0; i < 10; i++ )); do
echo "${i}";
done
for i in a b c d e; do
echo "${i}";
done
echo "====================while 语句===================="
int=1
while [[ "${int}" -le 5 ]]; do
echo "${int}";
# let int+=1;
# let "int++";
# let int=int+1;
int=`expr $int + 1`;
done
#三种无限循环方式
echo "无限循环1"
# while :
# do
# echo "无限循环1";
# done;
echo "无限循环2"
# while true
# do
# echo "无限循环2";
# done;
echo "无限循环3"
# for ((; ;));do
# echo "无限循环3";
# done;
echo "until 循环####################################"
# until 循环执行一系列命令直至条件为 true 时停止。
# until 循环与 while 循环在处理方式上刚好相反。
# 一般 while 循环优于 until 循环,但在某些时候—也只是极少数情况下,until 循环更加有用。
# 语法格式
a=0
until [[ $a -gt 10 ]]; do
echo "${a}";
a=`expr $a + 1`;
done
echo "case 语句##################################"
read -p "请输入1~4之间的数字" num;
echo "您输入数字:${num}";
case $num in
1 ) echo "您输入了 ${num}"
;;
2 ) echo "您输入了 ${num}"
;;
3 ) echo "您输入了 ${num}"
;;
4 ) echo "您输入了 ${num}"
;;
* ) echo "您输入的数字不在1~4之间"
;;
esac
echo "演示无线循环,break,终止循环##################################"
while :
do
read -p "请输入1~4之间的数字" p;
echo "echo您输入的是:${p}";
case "${p}" in
1|2|3|4 ) echo "您输入的是${p}"
;;
*) echo "您输入的是${p},不在1~4之间,break终止循环"
break;
;;
esac
done
echo "演示无线循环,continue跳出当前循环##################################"
while :
do
read -p "请输入1~4之间的数字" p;
echo "echo您输入的是:${p}";
case "${p}" in
1|2|3|4 ) echo "您输入的是${p}"
;;
*) echo "您输入的是${p},不在1~4之间,continue跳出循环"
continue;
echo "game over!"
;;
esac
done