if 测试条件 then; 或 if 测试条件 then 代码分支代码分支 fifi 双分支的if语句: if 测试条件;then 条件为真时执行的分支 else 条件为假时执行的分支 fi 多分支if语句 if CONDITION1;then 条件1为真分支 elif CONDITION2;then 条件2为真分支 elif CONDITION3;then 条件3为真分支 ... else 所有条件均不满...
Conditions in bash scripting (if statements) - Linux Academy Blog https://linuxacademy.com/blog/linux/conditions-in-bash-scripting-if-statements/ Table of conditions The following table list the condition possibilities for both the single- and the double-bracket syntax. Save a single exception, th...
if [ condition ] --注意括号两边有空格,condition 是个条件表达式 then commands fi 作用:判断 ccondition 条件是否成立,如果成立,执行中间的命令 commands 不成立不执行。 如: if [ $a -gt $b ] then echo "a大于b" fi if 可以接 条件表达式 如 if [ $a -gt $b ],也可以直接接一个命令 如if m...
4.bash的执行过程1>命令的执行是从上到下,从左到右的分析与执行2>命令执行时,命令和参数间的多个空白都会被忽略3>空白行也会被忽略4>没读取一个Enter字符,就开始执行该程序5>“#”作为批注,任何加在#后面的数据都将视为批注6>shell script 都是以*.sh结尾,而且一个shell脚本能否被执行,必须得有x权限7>ba...
script first checks if ‘a’ is greater than ‘b’. If it’s not, it moves on to the ‘elif’ statement to check if ‘a’ is greater than ‘c’. If neither condition is met, it executes the ‘else’ statement, which in this case, prints ‘a is not greater than either b or ...
(dirname"$SCRIPT_DIR")exportCATKIN_DIR="$HOME/catkin_ws"source /opt/ros/$ROS_DISTRO/setup.bashmain(){install_catkin_toolscreate_catkin_ws}install_catkin_tools(){# Checkifalready installediftype catkin > /dev/null2>&1; thenecho"Catkin tools is ...
A Shell script usually needs to test if a command succeeds or a condition is met. In Bash, this test can be done with a Bash if statement. As with any other programming language, Bash comes with conditional expressions that allow you to test for conditions and alter the control flow if ...
if语句 条件测试 bash条件判断之if语句(二) 练习19:写一个脚本:可以接受一个参数,其使用形式如下:script.sh {start|stop|restart|status}如果参数为start,创建空文件/var/lock/subsys/script,并显示“Starting script successfully.”;如果参数为stop,则删除文件/var/lock/subsys/script,并显示“Stop script if语...
/bin/bashif[`whoami`!='root'];then echo"Executing the installer script"./home/oracle/databases/runInstaller.shelseecho"Root is not allowed to execute the installer script"fi Executing the scriptasa root user,#./preinstaller.sh Root is not allowed to execute the installer script...
if [ $age -gt 18 ] && [ "$grade" == "A" ] then echo "Congratulations! You are eligible for a scholarship." else echo "Sorry, you are not eligible for a scholarship." fi Nested If statement In your bash script, you have the flexibility to incorporate multiple if statements as need...