tr

# tr
translate 的简写，man page，要用管道或重定向将文本传入到tr

## 说明
```
Usage: tr [OPTION]... SET1 [SET2]
Translate, squeeze, and/or delete characters from standard input,
writing to standard output.

-c, -C, --complement    use the complement of SET1
  -d, --delete            delete characters in SET1, do not translate
  -s, --squeeze-repeats   replace each input sequence of a repeated character
                            that is listed in SET1 with a single occurrence
                            of that character
  -t, --truncate-set1     first truncate SET1 to length of SET2
      --help     display this help and exit
      --version  output version information and exit

SETs are specified as strings of characters.  Most represent themselves.
Interpreted sequences are:

\NNN            character with octal value NNN (1 to 3 octal digits)
  \\              backslash
  \a              audible BEL
  \b              backspace
  \f              form feed
  \n              new line
  \r              return
  \t              horizontal tab
  \v              vertical tab
  CHAR1-CHAR2     all characters from CHAR1 to CHAR2 in ascending order
  [CHAR*]         in SET2, copies of CHAR until length of SET1
  [CHAR*REPEAT]   REPEAT copies of CHAR, REPEAT octal if starting with 0
  [:alnum:]       all letters and digits
  [:alpha:]       all letters
  [:blank:]       all horizontal whitespace
  [:cntrl:]       all control characters
  [:digit:]       all digits
  [:graph:]       all printable characters, not including space
  [:lower:]       all lower case letters
  [:print:]       all printable characters, including space
  [:punct:]       all punctuation characters
  [:space:]       all horizontal or vertical whitespace
  [:upper:]       all upper case letters
  [:xdigit:]      all hexadecimal digits
  [=CHAR=]        all characters which are equivalent to CHAR

Translation occurs if -d is not given and both SET1 and SET2 appear.
-t may be used only when translating.  SET2 is extended to length of
SET1 by repeating its last character as necessary.  Excess characters
of SET2 are ignored.  Only [:lower:] and [:upper:] are guaranteed to
expand in ascending order; used in SET2 while translating, they may
only be used in pairs to specify case conversion.  -s uses SET1 if not
translating nor deleting; else squeezing uses SET2 and occurs after
translation or deletion.

Report tr bugs to bug-coreutils@gnu.org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
For complete documentation, run: info coreutils 'tr invocation'
```

## 示例
感觉help或者man page不是很容易懂可以借助示例来理解。
### 大写转小写
- 第一种方法

```shell
echo 'ALTER SYSTEM SET DB_RECOVERY_FILE_DEST_SIZE=8g;' | tr 'A-Z' 'a-z'
```

- 第二种方法

```shell
echo 'ALTER SYSTEM SET DB_RECOVERY_FILE_DEST_SIZE=8g;' | tr [:upper:] [:lower:]
```

### 替换
类似sed，看来中文是没法大小写转换的
```
[oracle@osa-orcl67 trace]$ echo '一' |tr [:lower:] [:upper:]
一
[oracle@osa-orcl67 trace]$ echo '一' |tr '一' '壹'
壹
```