[转帖]shell中大写小转换

shell,中大,转换 · 浏览次数 : 0

小编点评

Sure, here's a summary of the different ways to add variables in bash 4.0 and use them in string manipulation: **Using tr:** * `tr '[:upper:]' '[:lower:]'abcDEF#` converts the first character of the variable to lowercase. * `tr '[:lower:]' '[:upper:]'hi allAWK` converts all characters to lowercase. * `tr '[:upper:]' '[:lower:]'hi allNon-POSIX` converts only the first character to lowercase. **Using declare:** * `declare -v variable_name="value"` declares a variable and assigns it a value. * `declare -a array_name=("value1" "value2" "value3")` creates an array and assigns values to it. **Using typeset:** * `typeset -a variable_name="value"` creates an array named `variable_name` and assigns a value to it. **Using assignment operators:** * `${variable_name,,}` accesses the variable with the first character removed and assigns the remaining characters to a new variable. * `${variable_name^^}` accesses the variable with the first character removed and assigns the remaining characters to a new variable. * `${variable_name,,}` accesses the variable with the first character removed and assigns the remaining characters to a new variable. **Using string manipulation commands:** * `${variable_name,,}` accesses the variable with the first character removed and assigns the remaining characters to a new variable. * `${variable_name^^}` accesses the variable with the first character removed and assigns the remaining characters to a new variable. * `${variable_name,,}` accesses the variable with the first character removed and assigns the remaining characters to a new variable. Remember to choose the method that best suits your needs and the complexity of your string manipulation task.

正文

https://www.cnblogs.com/byfboke/p/14272195.html

用tr需要新增变量，用declare或typeset需要在变量赋值前或者赋值后单独声明，都有些麻烦

此方法为bash 4.0以后新增，bash 4.0 2009年发布

$ test="abcDEF"

# 把变量中的第一个字符换成大写

$ echo ${test^}
AbcDEF

# 把变量中的所有小写字母，全部替换为大写
$ echo ${test^^}
ABCDEF

# 把变量中的第一个字符换成小写
$ echo ${test,}
abcDEF

# 把变量中的所有大写字母，全部替换为小写
$ echo ${test,,}
abcdef

https://stackoverflow.com/questions/2264428/how-to-convert-a-string-to-lower-case-in-bash

The are various ways:

POSIX standard

tr

$ echo "$a" | tr '[:upper:]' '[:lower:]'
hi all

AWK

$ echo "$a" | awk '{print tolower($0)}'
hi all

Non-POSIX

You may run into portability issues with the following examples:

Bash 4.0

$ echo "${a,,}"
hi all

sed

$ echo "$a" | sed -e 's/\(.*\)/\L\1/'
hi all
# this also works:
$ sed -e 's/\(.*\)/\L\1/' <<< "$a"
hi all

Perl

$ echo "$a" | perl -ne 'print lc'
hi all

Bash

lc(){
    case "$1" in
        [A-Z])
        n=$(printf "%d" "'$1")
        n=$((n+32))
        printf \\$(printf "%o" "$n")
        ;;
        *)
        printf "%s" "$1"
        ;;
    esac
}
word="I Love Bash"
for((i=0;i<${#word};i++))
do
    ch="${word:$i:1}"
    lc "$ch"
done

分类: 工作时候遇到的报错解决, 脚本