tr_cmd.md

Translate Command (tr)

The tr command allows the user to translate (map) characters in files from one value to another.

tr only accepts input from standard input and produces output on standard output. User must provide redirection to specify input/output files (See Redirect for details).

Mapping characters.

Simple character mapping

$ cat input_users.txt
USER_ID:ACCT_NUM:USER_NAME
3:5555:David
...

$ tr ':' '|' < input_users.txt
USER_ID|ACCT_NUM|USER_NAME
3|5555|David
...

Character class mapping

# Map range ['a','z'] to range ['A','Z']
$ tr ‘[a-z]’ ‘[A-Z]’ < input_users.txt
USER_ID:ACCT_NUM:USER_NAME
3:5555:DAVID
...

# same as above, but uses language independent classes.
tr ‘[:lower:]’ ‘[:upper:]’ < input_users.txt
USER_ID:ACCT_NUM:USER_NAME
3:5555:DAVID
...

Deleting characters

tr can also be used to delete undesired characters. The example below will delete all carriage returns from the dos file (effectively turning it into a unix format text file).

$ od -c -t x1 < dosfile.txt
0000000    h   e   l   l   o  \r  \n   b   y   e  \r  \n
           68  65  6c  6c  6f  0d  0a  62  79  65  0d  0a
0000014

$ tr -d '\r' < dosfile.txt | od -c -t x1
0000000    h   e   l   l   o  \n   b   y   e  \n
           68  65  6c  6c  6f  0a  62  79  65  0a
0000012