Use of Linux tr command

1. Introduction

tr is used to convert or delete a piece of text. tr is the abbreviation of translate, and its function in English is: translate or delete characters. All the functions of tr can be completed by sed, and tr can be regarded as a minimalist implementation of sed.

2. Format

tr [OPTION]... SET1 [SET2]

3. Options

-c, -C, --complement: Delete characters other than character set <character set1> or convert them to the last character in character set <character set2> (if you specify multiple characters). See Example 6.
-d, --delete: Delete the string SET1 in the information.
-s, --squeeze-repeats: Squeeze repeated characters and keep only one.
--help: Display help information.
--version: Display version information.

4. Examples

(1) Change all lowercase characters in the information output by last to uppercase characters.

last|tr '[az]' '[AZ]'
//or last|tr [az] [AZ]

(2) Delete the colon ":" from the information output by /etc/passwd.

cat /etc/passwd | tr -d ':'

(3) Convert DOS files into Unix files.

cat /etc/passwd | tr -d '\r'

(4) Delete blank lines

cat file | tr -s "\n" > new_file

(5) Replace "abc" that appears in the file with "xyz".

cat file | tr "abc" "xyz" > new_file

Note: Here, all occurrences of the letter "a" in the file are replaced with the letter "x", the letter "b" is replaced with the letter "y", and the letter "c" is replaced with the letter "z", rather than replacing the string "abc" with the string "xyz".

(6) Delete and replace characters outside the specified character set.

//Replace characters outside the specified character set [b3335@MIC ~]$ echo alv blv|tr -c 'lv ' "x"
xlv xlv

//Delete characters outside the specified character set [b3335@MIC ~]$ echo alv blv|tr -cd 'lv'
lvlv

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