Linux的jot源码包,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.-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 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

See

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