[SOLVED] Removing a newline character at the end of a file

Issue

To remove all newlines you could, say:

tr -d '\n' < days.txt
cat days.txt | tr -d '\n'

but how would you use tr to remove just the newline at the end/bottom of a text file?

I'm not sure to specify just the last one.

Solution

Take advantage of the fact that a) the newline character is at the end of the file and b) the character is 1 byte large: use the truncate command to shrink the file by one byte:

# a file with the word "test" in it, with a newline at the end (5 characters total)
$ cat foo 
test

# a hex dump of foo shows the '\n' at the end (0a)
$ xxd -p foo
746573740a

# and `stat` tells us the size of the file: 5 bytes (one for each character)
$ stat -c '%s' foo
5

# so we can use `truncate` to set the file size to 4 bytes instead
$ truncate -s 4 foo

# which will remove the newline at the end
$ xxd -p foo
74657374
$ cat foo
test$ 

You can also roll the sizing and math into a one line command:

truncate -s $(($(stat -c '%s' foo)-1)) foo

Answered By - Christopher Neylan

Answer Checked By - Dawn Plyler (WPSolving Volunteer)