Bash:共通コマンドツール-trコマンド

trコマンドは簡単な文字の置換と削除に使用できます.よく使われるのは-d、-sオプションです.置換と削除は単一の文字で行われます
次のテキストがあるとします.

Read from the file words.txt 
and output the word frequency list 
to stdout.

USE CASE 1:
テキストをすべて大文字に変換

$ cat text.txt | tr [a-z] [A-Z]

READ FROM THE FILE WORDS.TXT

AND OUTPUT THE WORD FREQUENCY LIST

TO STDOUT.

trコマンドの[a-z]は置換が必要な文字の集合であり、[A-Z]は置換後の文字の集合であり、それらは一つ一つ対応する関係である(aはA、bはB...).trコマンドは、次のような文字列の置換作業を行うことはできません.

$ cat text.txt | tr "the" "an"

Rnad from ann filn words.axa

and ouapua ann word frnqunncy lisa

ao sadoua.

theはanに置き換えられるのではなく,再び文字ごとに置き換えられていることがわかる(t->a,h-->n,e->n),この点に注意が必要である.
USE CASE 2:
テキストの単語を1行1つに抽出

$ cat text.txt | tr -s " " "
"

Read

from

the

file

words.txt

and

output

the

word

frequency

list

to

stdout.

ここでは-sパラメータを使用して重量を除去します.ここでの重量除去は、指定した文字が置き換えられた後、隣接する重複が見つかった場合、-sパラメータを追加しない場合は、1つだけ保持されます.

$ cat text.txt | tr  " " "
"

Read

from

the

file

words.txt



and

output

the

word

frequency

list



to

stdout.

余ったレンタカーが出てくるのが見えます.もっと極端な例を挙げます.

$ echo "AAaaaaabbBBbb"|tr -s [ab] [AB]

AB

-sパラメータを使用すると、置換後に連続的に繰り返される文字が1つしか残っていないことがわかります.
path変数の表示:

$ echo $PATH

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games

$ echo $PATH|tr -s ":" "
"

/usr/local/sbin

/usr/local/bin

/usr/sbin

/usr/bin

/sbin

/bin

/usr/games

/usr/local/games

USE CASE 3:
指定文字の削除

$ date|tr -d [A-Za-z]

  17 14:45:56  2015

参照先:http://blog.sina.com.cn/s/blog_58c3f7960100uttl.html

NAME

       tr - translate or delete characters



SYNOPSIS

       tr [OPTION]... SET1 [SET2]



DESCRIPTION

       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



       
     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.