Linux string操作

1. 长度

${#string}

myString="abc123abc456"

echo ${#myString}               # 12

expr length $string

myString="abc123abc456"

expr length ${myString}         # 12

2. 索引

expr index $string $substring

myString="abc123abc456"

expr index "$myString" "123"        # 4

3. 子集

${string:position}

${string:position:length}

myString="abc123abc456"             

echo ${myString:0}                  # abc123abc456
echo ${myString:4}                  # 23abc456

echo ${myString:3:3}                # 123

4. 左右清除

${string#substring}, 从左往右, 移除最小匹配

${string##substring}, 从左往右, 移除最大匹配

${string%substring}, 从右往左, 移除最小匹配

${string%%substring}, 右右往左, 移除最大匹配

myString="abc123abc456"

echo ${myString#a*c}                # 123abc456
echo ${myString##a*c}               # 456

echo ${myString%c*}                 # abc123ab
echo ${myString%%c*}                # ab

5. 替换

${string/substring/replacement}, 只替换第一个匹配子集

${string//substring/replacement}, 替换全部匹配子集

myString="abc123abc456"

echo ${myString/abc/XYZ}            # XYZ123abc456
echo ${myString//abc/XYZ}           # XYZ123XYZ456