tr is an UNIX utility for translating, or deleting, or squeezing repeated characters. It will read from STDIN and write to STDOUT.
tr stands for translate.
Syntax
The syntax of tr command is:
$ tr [OPTION] SET1 [SET2]
Translation
If both the SET1 and SET2 are specified and ‘-d’ OPTION is not specified, then tr command will replace each characters in SET1 with each character in same position in SET2.
1. Convert lower case to upper case
The following tr command is used to convert the lower case to upper case
$ tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ thegeekstuff THEGEEKSTUFF
The following command will also convert lower case to upper case
$ tr [:lower:] [:upper:] thegeekstuff THEGEEKSTUFF
You can also use ranges in tr. The following command uses ranges to convert lower to upper case.
$ tr a-z A-Z thegeekstuff THEGEEKSTUFF
2. Translate braces into parenthesis
You can also translate from and to a file. In this example we will translate braces in a file with parenthesis.
$ tr '{}' '()' < inputfile > outputfile
The above command will read each character from “inputfile”, translate if it is a brace, and write the output in “outputfile”.
3. Translate white-space to tabs
The following command will translate all the white-space to tabs
$ echo "This is for testing" | tr [:space:] '\t' This is for testing
4. Squeeze repetition of characters using -s
In Example 3, we see how to translate space with tabs. But if there are two are more spaces present continuously, then the previous command will translate each spaces to a tab as follows.
$ echo "This is for testing" | tr [:space:] '\t' This is for testing
We can use -s option to squeeze the repetition of characters.
$ echo "This is for testing" | tr -s [:space:] '\t' This is for testing
Similarly you can convert multiple continuous spaces with a single space
$ echo "This is for testing" | tr -s [:space:] ' ' This is for testing
5. Delete specified characters using -d option
tr can also be used to remove particular characters using -d option.
$ echo "the geek stuff" | tr -d 't' he geek suff
To remove all the digits from the string, use
$ echo "my username is 432234" | tr -d [:digit:] my username is
Also, if you like to delete lines from file, you can use sed d command.
6. Complement the sets using -c option
You can complement the SET1 using -c option. For example, to remove all characters except digits, you can use the following.
$ echo "my username is 432234" | tr -cd [:digit:] 432234
7. Remove all non-printable character from a file
The following command can be used to remove all non-printable characters from a file.
$ tr -cd [:print:] < file.txt
8. Join all the lines in a file into a single line
The below command will translate all newlines into spaces and make the result as a single line.
$ tr -s '\n' ' ' < file.txt
My name is Ramesh Natarajan. I will be posting instruction guides, how-to, troubleshooting tips and tricks on Linux, database, hardware, security and web. My focus is to write articles that will either teach you or help you resolve a problem. Read more about
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Hello
How can I order in script lower words to upper the first letter of word only ?
ex: ramesh natarajan > Ramesh Natarajan
Thank you!
Hi,
Thanks for nice article.
Hi “mre”
tr can not solve your problem…
Hi,
I think, that [:lower:], [:digit:], …. must be quoted
to protect this symbolic names against filename expansion!
Command line example:
$ touch d i g t
$ tr [:digit:] ‘*’
tr: extra operand `i’
Try `tr –help’ for more information.
$
With regards,
Goxxi
8) Join all the lines in a file into a single line
The below command will translate all newlines into spaces and make the result as a single line.
$ tr -s ‘\n’ ‘ ‘ < file.txt
also can use tr '\n' <file.txt # here we get the same result without using -s (switch)
Nice article.
echo “This is for testing” | tr [:space:] ‘\t’ …
This command works only wen I enclose single quotes in between ‘[:space:]’..
i.e echo “This is for testing” | tr ‘[:space:]’ ‘\t’
echo “welcome”|tee word|cut -c1|tr [a-z] [A-Z]|tee word1|echo “`cat` `cat word`”|cut -c1,4-10.
this will work to make the first letter of word to be capital
how to replace multiple characters with only one given characters ?
This is how you can change multiple characters to only one character
echo `tr wabd A filename to save the output
@bhupender singh
hey,
I don think ‘wabd’ are options for tr; check by `man tr` command…
@bhupender singh
hey,
I don think ‘wabd’ are options for tr; check by `man tr` command…
how to delete all control symbols from a line except NULL and new line?
I try
tr -d [[:cntrl:]]
but i need to save \n
fast commend is not working
fast commmend ANS -tr -s ” [a-z]” “[A-Z” < file name
Dear Lakshmanan,
Your tr of lower to upper is incorrect. You need to surround the brackets in single quotes.
Sincerely,
Vijay
Hi! Thanks for the article.
I am trying to to use your command from nr 2 to change all text within a file from lower to upper. however bash just deletes everything!
tr [:lower:] [:upper:] text.txt
any advice on how i could avoid this? i want to overwrite the same file basically input and output at the same location. thx!
@Bensen
If this is your exact command
tr [:lower:] [:upper:] text.txt
Then it needs to be changed to
tr [:lower:] [:upper:] < text.txt
You need to redirect the file content, using '<' , to the 'tr' command
[root@abc alam]# cat kbc |tr [:lower:] [:upper:]
HI ALAM HOW ARE YOU []
I [AM FINE] BRO
[root@nldtlx07 alam]#
How can I also translate the braces in same command
cat kbc |tr [:lower:] [:upper:] && [] {}====> Its not working
How can I change a text file with only NL line separators to a DOS one?
Hi, i working on an assignment where i have to encrypt a text file.
I finish most of the sub part but i could not solve the main part.
Im suppose to add a “key” into a-z. for example, the key is ZEROZEBRA->ZEROBA
( i also have to remove the alphabet if they are the same)
plaintext alphabet ->abcdefghijklmnopqrstuvwxyz
ciphertext alphabet->zerobacdfghijklmnpqstuvwxy
notice that key is place to the left and the order of the alphabet is changed
After that, i use the ciphertext to encrypt a text file( i done this part).
How do you combine many [SET1](s) and [SET2](s) into one tr -d command? I want to see an example of this. For example, I want to remove both the ’00’ and ‘E-‘ in one tr -d command from a file1.
Thanks, it helped me, I like the organisation of this tuto, it realy saves a time then reading the documentation topic of command 🙂
how to replace a character with multiple table.For example I need to replace a by 4 tabs
what happens in converting lower case to upper case letter if the 2nd string had more characters than 1st character
Thanks for the hints. I had to remove colon from a “MAC” address (of an ethernet card). The following worked…
echo $MACADDRESS | tr -d ‘:’
Of course, I needed to replace “MACADDRESS” with the actual MAC address.
I’d add a simple, but useful #9 example:
tr ‘\0’ ‘\n’ < /proc//environ
to inspect the environment of a running process.
The ‘environ’ files use the C convention of terminating strings with a NULL character, which makes them difficult to process e.g. with grep.