Linux指令篇:字串處理--expr

名稱：expr

### 字串長度

shell>> expr length "this is a test"
14

### 數字商數

shell>> expr 14 % 9
5

### 從位置處抓取字串

shell>> expr substr "this is a test" 3 5
is is

### 數字串 only the first character

shell>> expr index "testforthegame" e
2

### 字串真實重現

shell>> expr quote thisisatestformela
thisisatestformela