[student@studentvm1 testdir]$ File="TestFile1" ; echo "This is $File" > $File ; if [ -s $File ] ; then echo "$File exists and contains data." ; elif [ -e $File ] ; then echo "$File exists and is empty." ; else
by the 'test' builtin, and may be combined using the following operators: ( EXPRESSION ) Returns the value of EXPRESSION ! EXPRESSION True if EXPRESSION is false; else false EXPR1 && EXPR2 True if both EXPR1 and EXPR2 are true; else false EXPR1 || EXPR2 True if either EXPR1 or EX...
[ ARG1 OP ARG2 ] “OP” is one of -eq, -ne, -lt, -le, -gt or -ge. These arithmetic binary operators return true if “ARG1” is equal to, not equal to, less than, less than or equal to, greater than, or greater than or equal to “ARG2”, respectively. “ARG1” and “AR...
or to 0 if the expression evaluates to a non-zero value. You do not need to escape operators between((and)). Arithmetic is done on integers. Division by 0 causes an error, but overflow does not. You may perform the usual C language arithmetic, logical...
Unary operators are often used to test the status of a file, a variable, a shell option (optname), or a string. Unary and Binary expressions are formed with the following primaries. Conditional ExpressionMeaning -a file True if file exists....
if条件是Bash脚本中用于进行条件判断的关键字。通过if条件,可以根据条件的真假来执行不同的代码块。if条件的语法如下: 代码语言:txt 复制 if condition then # code block executed if condition is true else # code block executed if condition is false fi 在if条件中,可以使用各种比较运算符(如等于、不等于...
了 Bash let 命令,它用于执行一个或多个表达式...,变量计算中不需要加上 $ 来表示变量 #8 #until 循环 #9收获运行sh文件 bash 1.sh #10收获 tar -czvf test.tar.gz a.c //压缩 a.c文件为test.tar.gz.../bin/bash #!...<<EOF your-password EOF bash教程 linux/linux-shell-basic-operators....
1 : This is a comment thar generates an error,(if [ $x -eq 3] ). ":"还用来在/etc/passwd和$PATH变量中用来做分隔符. bash$ echo $PATH /usr/local/bin:/bin:/usr/X11R6/bin:/sbin:/usr/sbin:/usr/games! 取反操作符,将反转"退出状态"结果,(见Example 6-2).也会反转test操作符的意义...
Always include spaces in your ‘if’ and ‘elif’ conditions. Use the correct operators for numerical and string comparisons. Indent your code properly to make it more readable. Test your scripts thoroughly to catch any errors. Use ‘case’ statements for pattern matching instead of long ‘elif...
the expression is true if the unary test is true. If the first argument is not a valid unary conditional operator, the expression is false. 3 arguments The following conditions are applied in the order listed. If the second argument is one of the binary conditional operators listed above unde...