abc : The string is not empty 文件测试运算符 实例: #!/bin/bash file="/home/shiyanlou/test.sh" if [ -r $file ] then echo "The file is readable" else echo "The file is not readable" fi if [ -e $file ] then echo "File exists" else echo "File not exists" fi 结果 The file ...
echo"$1 exists." else echo"$1 is not exists." fi #运行脚本时,后接参数root,youshine,ehhe就是通过$1传递给脚本的 练习中的/dev/null,是黑洞,当我们不需要命令返回信息时,即可指向它。 if语句中通过命令执行的状态返回值(可以在当前命令执行后,echo $?查看)进行判断, 0表示成功执行,1-255表示执行失...
if [ $Shell == /bin/bash ]; then #如有需要此处的字符或变量用双引号,如字符间有空格时 echo "$1's shell is bash." Ret=5 else echo "$1's shell is not bash." Ret=7 fi else echo "$1 is not exists." Ret=9 fi done exit $Ret #echo $? 状态返回值即可判断执行的是脚本中哪一...
if: if 命令; then 命令; [ elif 命令; then 命令; ]... [ else 命令; ] fi ---用fi作结尾,与if遥相呼应 if执行结构包括单分支、双分支以及多分支执行结构: if语句的单分支结构: if 命令; then 命令; fi 注意:是否会执行then后面的命令,取决于if后面的命令的执行状态返回值; 1.如果返回值为真,...
This is the job of the test command, which can check if a file exists and its type. Since only the check is completed, the test command sets the exit code to 0 or 1 (either false or true, respectively) whether the test is successful or not. ...
TestFile1 does not exist or is empty. 向文件添加一些内容,然后再测试一次: [student@studentvm1 testdir]$ File="TestFile1" ; echo "This is file $File" > $File ; if [ -s $File ] ; then echo "$File exists and contains data." ; else echo "$File does not exist or is empty." ...
# If not running interactively, don't do anythingcase$-in *i*);;*)return;;esac 就是为了避免非交互模式随便运行一条命令都要解析后面的各种配置用的。 当然,新版本的 bash 如果以非交互模式启动,会直接跳过 ~/.bashrc 的解析,而这几行 bashrc 中的检测为了兼容被保留了下来。
anny ~> ./msgcheck.sh This scripts checks the existence of the messages file. Checking... /var/log/messages exists. ...done. 7.1.1.4. 检查shell选项 加入到你的Bash配置文件中去: # These lines will print a message if the noclobber option is set: ...
x=5; if [ $x = 5 ]; then echo 'x equals 5.'; else echo 'x does not equal...
执行命令区域，否则 不进入循环，介绍while 命令 行3，执行命令区域，这些命令中，Bash，Unix shell的...