shell:判斷某個變量是否包含字符串/變量的方法


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


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