如何将bash数组的所有元素转换为小写？

Question

我在bash中有一个数组。

WHITELIST=(
    "THIS" 
    "examPle" 
    "somTHing" 
) 

如何将所有元素转换为现有或新数组中的小写？

Answer 1

您可以将整个数组转换在o NE拍摄：

WHITELIST=("${WHITELIST[@],,}") 
printf "%s\n" "${WHITELIST[@]}" 

this 
example 
somthing 

Answer 2

您可以使用${parameter,,}：

WHITELIST=(
     "THIS" 
     "examPle" 
     "somTHing" 
     ) 

i=0 
for elt in "${WHITELIST[@]}" 
do 
    NEWLIST[$i]=${elt,,} 
    i=$((${i} + 1)) 
done 

for elt in "${NEWLIST[@]}" 
do 
    echo $elt 
done 

从手册页：

${parameter,,pattern} 
      Case modification. This expansion modifies the case of alpha‐ 
      betic characters in parameter. The pattern is expanded to pro‐ 
      duce a pattern just as in pathname expansion. The^operator 
      converts lowercase letters matching pattern to uppercase; the , 
      operator converts matching uppercase letters to lowercase. The 
      ^^ and ,, expansions convert each matched character in the 
      expanded value; the^and , expansions match and convert only 
      the first character in the expanded value. If pattern is omit‐ 
      ted, it is treated like a ?, which matches every character. If 
      parameter is @ or *, the case modification operation is applied 
      to each positional parameter in turn, and the expansion is the 
      resultant list. If parameter is an array variable subscripted 
      with @ or *, the case modification operation is applied to each 
      member of the array in turn, and the expansion is the resultant 
      list. 

Answer 3

一个这样做的方式：

$ WHITELIST=("THIS" "examPle" "somTHing") 
$ x=0;while [ ${x} -lt ${#WHITELIST[*]} ] 
    do WHITELIST[$x]=$(tr [A-Z] [a-z] <<< ${WHITELIST[$x]}) 
    let x++ 
done 
$ echo "${WHITELIST[@]}" 
this example somthing