Squoggle

The tr command:

It’s short for “translate” but might be easier to remember thinking of it as “truncate”. The man page has this to say about it:

DESCRIPTION
Translate, squeeze, and/or delete characters from standard input, writing to standard output.

There are probably books written on what tr can do. I’m just going to leave some notes here on how I typically use it.

The tr program reads from standard input and writes to standard output.

Convert multiple lines of text into a single line of text:

Consider a file named file containing the following data:

abcde
fghij
klmno
pqrst
uvwxy

You want to convert the multiple lines into a single line of text. You can do that using tr with something like this:

$ cat file | tr -d '\n'

The result of the command is written to standard output as:

abcdefghijklmnopqrstuvwxy

The -d option deletes. In this case we’re deleting the newline character.

Replace comma with newline:

Sometimes you need to convert a single delimited line to multiple lines. Consider the following file named file containing the following data:

abcde,fghij,klmno,pqrst,uvwxy

We can translate the comma in the file into a new line character with the following command:

$ cat file | tr ',' '\n'

The results look like this:

abcde
fghij
klmno
pqrst
uvwxy