#!/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...
[student@studentvm1 testdir]$ X=1 ; if [ $X -eq 1 ] ; then echo "X equals 1" ; else echo "X does not equal 1" ; fi X equals 1 [student@studentvm1 testdir]$ X=0 ; if [ $X -eq 1 ] ; then echo "X equals 1" ; else echo "X does not equal 1" ; fi X does n...
Chanix-LGdeMacBook-Pro:shell_test chanix$ echo $@ Chanix-LGdeMacBook-Pro:shell_test chanix$ set -- "$@" "-h" Chanix-LGdeMacBook-Pro:shell_test chanix$ echo $@ -h 44. = 等号 等号(Equals)。 \1. 赋值操作,给变量赋值,在等号两侧禁止有空格; \2. 在比较测试中作为比较符出现,这...
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...
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?
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”. $ test 1 -eq 2 && echo“true” || echo“false” Let’s break it down. test: The test...
TestFile1doesnotexistorisempty. 1. 2. 向文件添加一些内容,然后再测试一次: 复制 [student@studentvm1 testdir]$File="TestFile1";echo"This is file $File">$File;if[-s $File];thenecho"$File exists and contains data.";elseecho"$File does not exist or is empty.";fi ...
“-n” flag to test if the next string to be inserted in the statement is some character or is empty. The character “*” has been added as a value to be multiplied by the iteration number. The first “for” loop ends and another “echo” statement will be used to just put the ...
In this case, the expression is slightly different, instead of typing true or false, thestdoutvariable is printed using$?. Check if strings are not equals The!=operator checks if String1 is not equal to String2. If the two strings are not equal, then it returns 0. If two strings are...
[student@studentvm1 testdir]$ X=1 ; if [ $X -eq 1 ] ; then echo "X equals 1" ; else echo "X does not equal 1" ; fi X equals 1 [student@studentvm1 testdir]$ X=0 ; if [ $X -eq 1 ] ; then echo "X equals 1" ; else echo "X does not equal 1" ; fi X does n...