Linux常用命令之tr
tr
NAME
- tr - translate or delete characters
- 可以对来自标准输入的字符进行替换、压缩和删除。它可以将一组字符变成另一组字符，经常用来编写优美的单行命令，作用很强大。
SYNOPSIS
tr [OPTION]... SET1 [SET2]
SET1
- 指定要转换或删除的原字符集。当执行转换操作时，必须使用参数“字符集2”指定转换的目标字符集。但执行删除操作时，不需要参数“字符集2”；
SET2
- 指定要转换成的目标字符集。
DESCRIPTION
Translate, squeeze, and/or delete characters from standard input,writing to standard output.
-c, -C, --complement
- use the complement of SET1
- 取代所有不属于第一字符集的字符
str="hello world"
# hello world
echo ${str}
# AAllAAAAAlA
echo ${str} | tr -c 'll\n' 'A'
# hello-world
echo ${str} | tr -c 'a-z\n' '-'
# hello-world
echo ${str} | tr -C 'a-z\n' '-'
-d, --delete
- delete characters in SET1, do not translate
- 删除所有属于第一字符集的字符；
str="hello world"
# hello world
echo ${str}
# helloworld
echo ${str} | tr -d ' '
# he wrd
echo ${str} | tr -d 'llo'
-s, --squeeze-repeats
- replace each sequence of a repeated character that is listed in the last specified SET, with a single occurrence of that character
- 把连续重复的字符以单独一个字符表示
str="thissss is a text linnnnnnne."
# thissss is a text linnnnnnne.
echo ${str}
# this is a text line.
echo ${str} | tr -s ' sn'
-t, --truncate-set1
- first truncate SET1 to length of SET2
- 先删除第一字符集较第二字符集多出的字符
str="hello world"
# hello world
echo ${str}
# heaao worad
echo ${str} | tr -t 'l' 'a'
# hello-world
echo ${str} | tr -t ' ' '-'
--help
- display this help and exit
--version
- output version information and exit
SETs are specified as strings of characters. Most represent
themselves. Interpreted sequences are:
\NNN character with octal value NNN (1 to 3 octal digits)
\\ backslash
\a audible BEL
\b backspace
\f form feed
\n new line
\r return
\t horizontal tab
\v vertical tab
CHAR1-CHAR2
all characters from CHAR1 to CHAR2 in ascending order
[CHAR*]
in SET2, copies of CHAR until length of SET1
[CHAR*REPEAT]
REPEAT copies of CHAR, REPEAT octal if starting with 0
[:alnum:]
all letters and digits
[:alpha:]
all letters
[:blank:]
all horizontal whitespace
[:cntrl:]
all control characters
[:digit:]
all digits
[:graph:]
all printable characters, not including space
[:lower:]
all lower case letters
[:print:]
all printable characters, including space
[:punct:]
all punctuation characters
[:space:]
all horizontal or vertical whitespace
[:upper:]
all upper case letters
[:xdigit:]
all hexadecimal digits
[=CHAR=]
all characters which are equivalent to CHAR
Translation occurs if -d is not given and both SET1 and SET2 appear.
-tmay be used only when translating. SET2 is extended to length of SET1 by repeating its last character as necessary. Excess characters of SET2 are ignored. Only[:lower:]and[:upper:]are guaranteed to expand in ascending order; used in SET2 while translating, they may only be used in pairs to specify case conversion. -s uses the last specified SET, and occurs after translation or deletion.
Example
#####################################################
# 字符集补集，从输入文本中将不在补集中的所有字符删除：
# 1 2 3 4
echo aa.,a 1 b#$bb 2 c*/cc 3 ddd 4 | tr -d -c '0-9 \n'
# 使用tr做数字相加操作：
# 45
echo 1 2 3 4 5 6 7 8 9 | xargs -n1 | echo $[ $(tr '\n' '+') 0 ]
# 除Windows文件“造成”的'^M'字符：
# cat file | tr -s "\r" "\n" > new_file
# cat file | tr -d "\r" > new_file
