嘗試了有3種方法：
1.使用“=~”符號，注意前后必須要有空格！
** 可以輸出正確結果,被匹配的字符串必須要有引號括起來！**
[clouder@ana53 bin]$ a1='hello.world'
[clouder@ana53 bin]$ a2='helloworld'
[clouder@ana53 bin]$ b='.'
[clouder@ana53 bin]$ if [[ ${a1} =~ '.' ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} =~ '.' ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a1} =~ "." ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} =~ "." ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a1} =~ "${b}" ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} =~ "${b}" ]];then echo "yes";else echo "no";fi
no
** 不能輸出正確結果 **
[clouder@ana53 bin]$ a1='hello.world'
[clouder@ana53 bin]$ a2='helloworld'
[clouder@ana53 bin]$ b='.'
[clouder@ana53 bin]$ if [[ ${a1} =~ . ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} =~ . ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a1} =~ ${b} ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} =~ ${b} ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a1} =~ '${b}' ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a2} =~ '${b}' ]];then echo "yes";else echo "no";fi
no
2.使用”==“加通配符wildcard，注意等號前后必須有空格，注意，通配符跟正則表達式有所區別，*表示匹配 0 或多個字符
** 可以輸出正確結果 **
[clouder@ana53 bin]$ a1='hello.world'
[clouder@ana53 bin]$ a2='helloworld'
[clouder@ana53 bin]$ if [[ ${a1} == *.* ]];then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if [[ ${a2} == *.* ]];then echo "yes";else echo "no";fi
no
** 不能輸出正確結果 ，通配符不能用括號括起來！**
[clouder@ana53 bin]$ a1='hello.world'
[clouder@ana53 bin]$ a2='helloworld'
[clouder@ana53 bin]$ if [[ ${a2} == "*.*" ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a1} == "*.*" ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a1} == '*.*' ]];then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if [[ ${a2} == '*.*' ]];then echo "yes";else echo "no";fi
no
3.使用echo + grep -q 選項
** 使用這種方法時匹配是否有"."會不正常，所以我們換成匹配普通字符，有沒有括號都可以 **
[clouder@ana53 bin]$ a1='hello.world'
[clouder@ana53 bin]$ a2='helloworld'
[clouder@ana53 bin]$ a3="helloworlda"
[clouder@ana53 bin]$ if ( echo ${a1} |grep -q a );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a2} |grep -q a );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a3} |grep -q a );then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if ( echo ${a1} |grep -q 'a' );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a2} |grep -q 'a' );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a3} |grep -q 'a' );then echo "yes";else echo "no";fi
yes
[clouder@ana53 bin]$ if ( echo ${a1} |grep -q "a" );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a2} |grep -q "a" );then echo "yes";else echo "no";fi
no
[clouder@ana53 bin]$ if ( echo ${a3} |grep -q "a" );then echo "yes";else echo "no";fi
yes