tr command is used as a character-based search and replace function.
If you're a bioinformaticist, you may find the need to replace all T characters from a DNA strand to U's to obtain the corresponding mRNA strand. We can do this in a one-liner with the
$ echo 'CATCGTAGCTAGTCACTG' | tr T U CAUCGUAGCUAGUCACUG
In biology, each DNA strand has a corresponding strand. G's pair to C's and T's pair to A's. Can we use
tr to find the corresponding strand?
$ echo 'CAGTCGTACGTACGT' | tr 'ATGC' 'TACG' GTCAGCATGCATGCA
You can use this function to map lowercase letters to uppercase.
$ echo 'what is up world?' | tr a-z A-Z WHAT IS UP WORLD?
You may also use redirection to direct an input file and write to some output.
$ cat fox.txt The quick brown fox jumped over the lazy dog. $ tr 'aeiou' 'AEIOU' < fox.txt ThE qUIck brOwn fOx jUmpEd OvEr thE lAzy dOg. $ tr 'aeiou' 'AEIOU' < fox.txt > vowelsCappedFox.txt # Output to vowelsCappedFox.txt
-d option, we can delete specific characters from a string.
$ echo 'Removing all vowels' | tr -d 'aeiou' Rmvng ll vwls
We can eliminate repeated instances of a letter with the squeeze option,
-s. This removes all repeated characters that occur in sequence.
$ echo '1111112222233333344444' | tr -s 123 12344444
We can generate an amateur secret message by mapping our lowercase characters to their inverse correspondence.
$ cat fox.txt | tr a-z zyxwvutsrqponmlkjihgfedcba Tsv jfrxp yildm ulc qfnkvw levi gsv ozab wlt.
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