"The tr utility copies the standard input to the standard output with substitution or deletion of selected characters." -
tr does not have any features to operate on files. It operates only on stdin. To use it on files you must use input redirection like
tr .... < filename.txt or pipes like
cat filename.txt | tr ...
Replace all non-letters with a carriage return
-s shrinks adjacent matches into a single match.
$ echo abcdefghijklmnopqrstuvwxyz | tr g-t '_' abcdef______________uvwxyz $ echo abcdefghijklmnopqrstuvwxyz | tr -c g-t '_' ______ghijklmnopqrst_______ $ echo abcdefghijklmnopqrstuvwxyz | tr -s g-t '_' abcdef_uvwxyz $ echo abcdefghijklmnopqrstuvwxyz | tr -cs g-t '_' _ghijklmnopqrst_$
In Doug McIlroy's critique of Donald Knuth's unique word count finder,
tr was used twice. Here's a somewhat modified version:
$ man tr | tr -cs A-Za-z '\n' | tr A-Z a-z | sort | uniq -c | sort -rn | head 96 the 45 in 44 characters 38 string 30 of 29 a 25 to 23 tr 22 character 21 is
tris often used with
[cut](cut.md), though I prefer
[awk](awk.md)most of the time.