Shell Implementation TR Delete replacement detailed _linux shell

The TR (translate abbreviation) is used primarily to remove control characters from files or to convert characters.

Syntax: TR [–c/d/s/t] [SET1] [SET2] #SET1: Character Set 1;set2: Character Set 2
-c:complement, replace the characters except SET1 with SET2.
-d:delete, delete all the characters in the SET1, and do not convert.
-s:squeeze-repeats, compresses the duplicated characters in the SET1.
-t:truncate-set1, convert SET1 to SET2, typically by default-T.

1. Remove duplicate characters

#删除空白行就是删除换行符/N.
#注意: There are only carriage returns on these blank lines, no spaces.

$ cat Test.txt

I Love linux!

Hello world!

The Shell is worthy to been studied.

#这里用换行符的转义字符 \ n.
#注意: Here the extra line breaks are removed with-s, and all line breaks are deleted if D is used.

$ Cat Test.txt | tr-s ["\ n"]
I Love linux!
Hello world!
The Shell is worthy to been studied.
#也可以用八进制符 \012,\012 and \ n are line breaks.
$ Cat Test.txt | Tr-s "[\012]"
I Love linux!
Hello world!
The Shell is worthy to been studied.

2, case-by-case interchange

# converts all lowercase letters in the statement into uppercase letters, where-t can be omitted.
$ echo "Hello World I Love You" |tr [-t] [A-z] [a-z]
HELLO World I Love You
# converts all uppercase letters in the statement into lowercase letters.
$ echo "Hello World I Love You" |tr [A-z] [a-z]
Hello World I Love You

# can also be converted using character classes.
# [: Lower:] stands for lowercase letters, [: Upper:] On behalf of uppercase letters.
$ echo "Hello World I Love You" |tr [: Lower:] [: Upper:]
HELLO World I Love You

3, delete the specified characters

$ cat Test.txt
Monday 09:00
Tuesday 09:10
Wednesday 10:11
Thursday 11:30
Friday 08:00
Saturday 07:40
Sunday 10:00
# Now you want to delete all characters except the processing week.
# d represents deletion, [0-9] represents all numbers, [:] for colons and spaces.
$ Cat Test.txt | Tr-d "[0-9][:]"
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday

4, use-C to make the replacement of the complementary set

# Sometimes in the text we only know some characters to keep, and many other characters, you can use the replacement of the complement.

$ cat Test.txt
Monday 09:00
Tuesday 09:10
Wednesday 10:11
Thursday 11:30
Friday 08:00
Saturday 07:40
Sunday 10:00

# We only need a week, the idea is to replace the letters, everything else.

# here, C: Replaces all characters except the letter with a newline character;-S: Removes extra line breaks.

$ cat Test.txt|tr-cs "[a-z][a-z]" "\ n"
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday

Summary: The conversion of uppercase and lowercase letters, the deletion of unwanted characters is more commonly used. TR syntax is simple and easy to use.