逻辑判断基本测试语法: 四、shell脚本中的if条件短路现象 所谓短路现象就是利用多条件表达式,比如条件1 && 条件2,当条件1为真是才会执行条件2。否则结果为假不会执行条件2。例如下面的语句: 启动程序A && echo "run success" cat file |grep "hello" && echo "hello is contain" #同样相反的也可以 启动程序...
# 检查portmap进程是否已经存在,若已经存在则输出 "Portmap service is running.";否则检查是否存在"/etc/rc.d/init.d/portmap"可执行脚本,存在则启动portmap服务,否则提示"no portmap script files" # ---Designed by UNIX.ROOT Email: UNIX.ROOT@hotmail.com ### pgrep portmap &> /dev/null if [ $...
在编写UNIX Shell脚本时，面对需要根据条件执行不同操作的情况，条件语句显得尤为重要。其中，if...else语句是Shell提供的基础决策工具，它允许你在一系列选项中选择执行。其基本形式有三种：if...fi, if...else...fi, 和 if...elif...else...fi，通过关系运算符检查条件。这些运算符在前文已有...
The following table list the condition possibilities for both the single- and the double-bracket syntax. Save a single exception, the examples are given in single-bracket syntax, but are always compatible with double brackets. 1. File-based conditions: With the double-parenthesis syntax, you can...
UNIX/Linux shell脚本 if语句的几个案例(适合Linux初学者), 小诺技术博客新地址:www.rsyslog.org,欢迎前来访问!if语法:1、单分支的if语句if条件测试命令then命令序列fi2、双分支的if语句if条件测试命令then命令序列1else命令序列2fi3、多分支的if语句(elif可以嵌套
在Unix/Linux shell中,if是一种流程控制语句,用于根据条件执行不同的代码块。以下是if语句的一般语法: if[ condition ];then# Code to be executed if the condition is truefi if[ condition ];then# Codetobe executedifthe conditionistrueelse# Codetobe executedifthe conditionisfalsefi ...
Mathematical Operator in Shell Script Meaning Normal Arithmetical/ Mathematical Statements But in Shell For test statement with if command For [ expr ] statement with if command -eq is equal to 5 == 6 if test 5 -eq 6 if [ 5 -eq 6 ] ...
Bash, short for "Bourne Again SHell," is a powerful scripting language used in Unix-based operating systems. One of the fundamental constructs in Bash programming is the if statement. The if statement allows you to control the flow of your script based on specific conditions. In this article...
This is an example of a branch. Based on the condition, “Does X = 5?” do one thing,“Say X equals 5,” otherwise do another thing, “Say X is not equal to 5.” 这就是一个分支的例子。根据条件,“Does X = 5?” 做一件事情,“Say X equals 5,”否则,做另一件事情,“Say X ...
UNIX Shell 里面比较字符写法: -eq 等于 -ne 不等于 -gt 大于 -lt 小于 -le 小于等于 -ge 大于等于 -z 空串 = 两个字符相等 != 两个字符不等 -n 非空串 --- 更为详细的说明: 运算符 描述 示例 文件比较运算符 -e filename 如果 filename 存在,则为真 [ -e /var/...