shell中怎么判斷變量是不是以字母開(kāi)頭的

lostoasis

想要判斷一個(gè)變量，如果這個(gè)變量是以小寫(xiě)字母開(kāi)頭的，就輸出這個(gè)變量，請(qǐng)問(wèn)下面這個(gè)為什么什么也不輸出~~~~~~~~~~~~~~~
#!/bin/bash
aa=backup
if [[ $aa == "^[a-z]*" ]]
then
echo $aa
fi

songyc_2015

使用    =~

lostoasis

不行啊，沒(méi)有結(jié)果輸出
[:c10user:/home/TT_DB/ttingtest/ttingtest1]$ cat li
#!/bin/bash
a=backup
if [[ $a =~ "^[a-z]*" ]]
then
echo $a
fi

[:c10user:/home/TT_DB/ttingtest/ttingtest1]$ li
[:c10user:/home/TT_DB/ttingtest/ttingtest1]$



回復(fù) 2# songyc_2015


   

wh7211

1. #!/bin/bash
   
2. a="backup"
   
3. if [[ "$a" =~ ^[a-z]* ]];then
   
4. echo "$a"
   
5. else
   
6. echo "no"
   
7. fi

復(fù)制代碼

lostoasis

感覺(jué)不對(duì)啊，a的值改成123backup,然后輸出123backup,沒(méi)有遵循以a-z字母開(kāi)通的原則：
[:c10user:/home/TT_DB/ttingtest/ttingtest1]$ cat li
#!/bin/bash
a="123backup"
if [[ "$a" =~ ^[a-z]* ]];then
echo "$a"
else
echo "no"
fi

[:c10user:/home/TT_DB/ttingtest/ttingtest1]$ li
123backup



回復(fù) 4# wh7211


   

tuyajie

不知道我說(shuō)沒(méi)說(shuō)清楚

1. [jay.liu@aliCloud ~]$ aa=\^\[a\-z\]\*
   
2. [jay.liu@aliCloud ~]$ echo $aa
   
3. ^[a-z]*
   
4. [jay.liu@aliCloud ~]$ if [[ $aa == "^[a-z]*" ]]
   
5. > then
   
6. > echo $aa
   
7. > fi
   
8. ^[a-z]*
   
9. 
   
10. [jay.liu@aliCloud ~]$ echo $aa
    
11. test
    
12. [jay.liu@aliCloud ~]$ if [[ $aa =~ ^[a-z]* ]]; then echo Y; else echo N; fi
    
13. Y
    
14. [jay.liu@aliCloud ~]$ if [[ $aa =~ "^[a-z]*" ]]; then echo Y; else echo N; fi
    
15. N

復(fù)制代碼

jason680

回復(fù) 5# lostoasis


$ a="backup"; if [[ "$a" =~ ^[a-z] ]];then echo $a; fi
backup

$ a="123backup"; if [[ "$a" =~ ^[a-z] ]];then echo $a; fi

$ a="backup"; if [[ "$a" =~ ^[a-z]+$ ]];then echo $a; fi
backup

$ a="backup123"; if [[ "$a" =~ ^[a-z]+$ ]];then echo $a; fi
   

聆雨淋夜

回復(fù) 5# lostoasis

用+不能用*  *能匹配到0個(gè)字符，在你的例子中用*就毫無(wú)意義了


   

wh7211

回復(fù) 5# lostoasis
把*換成+，比如："$a" =~ ^[a-z]+