This page refers to the tr command, an translate command used to translate strings or patterns from one set of characters to another.

Translate does not take a filename as an argument, it only acts on a stream of characters.

Example: 

Hamish 35

We now want to translate that to: 

HAMISH 35

without editing the file. Cat-ting our file (columns.txt) and then piping the output of the cat command to the input of the translate command causing all lowercase names to be translated to uppercase names. 

cat columns.txt | tr '[a-z]' '[A-Z]'

Remember we have not modified the file columns.txt so how do we save the output? Simple, by redirecting the output of the translate command with ‘>’ to a file called UpCaseColumns.txt with: 

cat columns.txt | tr '[a-z]' '[A-Z]' > UpCaseColumns.txt

References: