arrays - bash配列のすべての要素を小文字に変換する方法は?

Question

bashに配列があります。

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

既存または新しい配列ですべての要素を小文字に変換するにはどうすればよいですか?

Answer 1

配列全体を一度に変換できます。

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

this
example
somthing

Answer 2

使用できます${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

マンページから：

  ${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

それを行う1つの方法：

$ 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