tr command in Unix

In this article, we will be discussing the use cases of the tr  Unix command with examples.

tr command

tr is used to  Translate characters.

Syntax
tr [-c] [-d] [-s] [string1] [string2]

-c	Complement the set of characters specified by string1.
-d	Delete all occurrences of input characters that are specified by string1.
-s	Replace instances of repeated characters with a single character.
string1	First string or character to be changed.
String2	Second-string or character to change the string1.

How to convert lower case to upper case

We can use the tr command without option -d,-c, and -s for that

$ echo $ORACLE_SID| tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ 
TECH
$ echo $ORACLE_SID| tr [a-z] [A-Z]
TECH
$ echo $ORACLE_SID| tr [:lower:] [:upper:]
TECH
$echo "good boy" | tr  good bad
bddd bdy

How to Delete specified characters using -d option

tr can also be used to remove particular characters using the -d option.

$ echo $ORACLE_SID 
TECH
$ echo $ORACLE_SID| tr -d ‘T’
ECH
$echo "good boy" | tr -d "g"
ood boy

How to use option -s to convert repeated occurrence of character into single character

tr ‘[A-Z]' ‘[a-z]' <1.txt | tr -cs 'a-z' '\n' | sort 

What this does is pass the contents of 1.txt to the tr command to translate uppercase letters to lowercase; the output from that is piped to another tr command that turns everything except lowercase letters into line breaks (effectively putting each word on a separate line); that’s piped to sort which puts the lines (words) in alphabetical order

How to use option -c with tr

-c can be used to find the complement of string1.

For example, to remove all characters except digits, you can use the following

$ echo " My id is MQ123452" | tr -cd [:digit:] 
 123452

I hope you like this content on tr command in Unix

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