Bash: difference between cat and echo

Question

This is file.txt (without an end-of-line for the last line):

foo:bar:baz:qux:quux
one:two:tree:four:five:six:seven
alpha:beta:gamma:delta:epsilon:zeta:eta:teta:iota:kappa:lambda:mu
the quick brown fox jumps over the lazy dog

File read.sh

while read -r line
do
    echo $line
done < file.txt

This is what I tried in the terminal:

./read.sh

Output:

foo:bar:baz:qux:quux
one:two:tree:four:five:six:seven
alpha:beta:gamma:delta:epsilon:zeta:eta:teta:iota:kappa:lambda:mu

Why doesn't read.sh show the last end of line like cat file.txt does?

Answer 1

Because there is no end of line in file.txt, if you:

$ od -c file.txt
0000000   f   o   o   :   b   a   r   :   b   a   z   :   q   u   x   :
0000020   q   u   u   x  \n   o   n   e   :   t   w   o   :   t   r   e
0000040   e   :   f   o   u   r   :   f   i   v   e   :   s   i   x   :
0000060   s   e   v   e   n  \n   a   l   p   h   a   :   b   e   t   a
0000100   :   g   a   m   m   a   :   d   e   l   t   a   :   e   p   s
0000120   i   l   o   n   :   z   e   t   a   :   e   t   a   :   t   e
0000140   t   a   :   i   o   t   a   :   k   a   p   p   a   :   l   a
0000160   m   b   d   a   :   m   u  \n   t   h   e       q   u   i   c
0000200   k       b   r   o   w   n       f   o   x       j   u   m   p
0000220   s       o   v   e   r       t   h   e       l   a   z   y    
0000240   d   o   g

There are no \n at the end of the file.

echo on the other other hand will always add a new line when you echo a message if there isn't one.

Answer 2

Other answers are right, there is simply no newline character in the end of your file.txt.

Most text editors will end a file with a newline automatically, even nano does that. But your file was generated by a script, right? To reproduce this behavior all you have to do is:

echo -n 'hello world' >> file.txt

-n flag tells echo not to output the trailing newline.

Also, if you want your read code to work, you can use this:

while read -r line
do
    printf "%s\n" "$line"
done < file.txt
[[ -n $line ]] && printf '%s' "$line"

This is going to work because actually read will place the last line into the variable, but it also will return false, thus breaking the while loop.