#!/bin/bash #: Description : print formatted sales report ## Build a long string of equals signs divider=== divider=$divider$divider ## Format strings for printf header="\n %-10s %11s %8s %10s\n" format=" %-10s %11.2f %8d %10.2f\n" ## Width of divider totalwidth=44 ## Pri...
String comparison with test Command Here are some string comparison examples using the test command. Check if the string is not empty The-nflag checks if the string length is non-zero. It returns true if the string is non-empty, else it returns false if the string is empty: $ [ -n "...
The equals sign "=" and the equality test-eqare not the same. The equals sign performs a character by character text comparison. The equality test performs a numerical comparison. We can see this by using thetestprogram on the command line. test "this string" = "this string" test "this...
[student@studentvm1 testdir]$ File="TestFile1" ; touch $File ; if [ -s $File ] ; then echo "$File exists and contains data." ; elif [ -e $File ] ; then echo "$File exists and is empty." ; else echo "$File does not exist." ; fi TestFile1 exists and is empty. [stude...
#!/bin/bash number1=5 number2=10 if ((number1 <= number2)); then echo "number1 is less than or equal to number2." else echo "number1 is greater than number2." fi As the number1 variable is lesser than the number2, it gave me the following output: String comparison operators...
[student@studentvm1 testdir]$ touch TestFile1 在这个简短的 CLI 程序中,修改$File变量的值相比于在多个地方修改表示文件名的字符串的值要容易: [student@studentvm1 testdir]$ File="TestFile1" ; if [ -e $File ] ; then echo "The file $File exists." ; else echo "The file $File does not...
How to check if a variable exists or is “null”? How to check if a file exists? How to check if a directory exists? How to check if a command succeeds or failed? How to do string comparison and check if a string equals to a value? How to check if a string is in an array?
如果if结构使用的不是test命令,而是普通命令,比如上一节的((...))算术运算,或者test命令与普通命令混用,那么可以使用 Bash 的命令控制操作符&&(AND)和||(OR),进行多个命令的逻辑运算。$ command1 && command2 $ command1 || command2对于&&操作符,先执行command1,只有command1执行成功后, 才会执行command2。
If you follow those rules then you can avoid accidentally overwriting data stored in environmental variables. You can assign data to a variable using the equals sign (=). The data you store in a variable can either be a string or a number. Let’s create a variable now on the command li...
Test usage Here’s a short example of how the test command works. We’ll be checking whether 1 equals 2. If true, then the output will be “true”. Otherwise, the output will be “false”. $test1-eq2&&echo“true”||echo“false” ...