shell编程笔记三：流程控制

格式：

if ....; then
  ....
elif ....; then
  ....
else
  ....
fi

[ -f "somefile" ] ：判断是否是一个文件

[ -x "/bin/ls" ] ：判断/bin/ls是否存在并有可执行权限

[ -n "$var" ] ：判断$var变量是否有值

[ "$a" = "$b" ] ：判断$a和$b是否相等 

示例：

#!/bin/bash

if [ ${SHELL} = "/bin/bash" ]; then
   echo "your login shell is the bash (bourne again shell)"
else
   echo "your login shell is not bash but ${SHELL}"
fi


判断登陆shell脚本是否为bash


while循环 if判断 多进程运行 休眠 日期 综合实例

while true
do
    nd=`date "+%H%M"`
    if [ "0010" == $nd ] || [ "1507" == $nd ];then
        echo "$nd was found"
        nohup /usr/local/bin/casperjs /syngooglebudget.js 1 >/cas1.txt 2>&1 &
        nohup /usr/local/bin/casperjs /syngooglebudget.js 2 >/cas2.txt 2>&1 &
        sleep 3600s
    else
        sleep 5s
        echo "couln'd foun $nd"
    fi
done