How to make 'cat' in Linux to interpret control characters

Question

Consider the following echo command:

 echo -e "at\r"

which produces the output at on the command line, i.e. the \r special character has been interpreted. I want to do the exact same thing with some text in a file. Supposing the exact same sequence

at\r

is written to a file named at.txt, then I want to display it on the terminal. But

cat at.txt

gives the output

at\r

what is not what I want. I want the special sequence \r to be interpreted, not just printed on the terminal. Anyone any idea?

Thanks Alex

Answer 1

Why not:

while read -r line; do echo -e $line; done < at.txt

Answer 2

You can simply:

echo -e $(cat at.txt)

Answer 3

The built-in echo command interprets the common backslash escapes. But in a file you have to interpret, or convert it in a similar way. The sed program can do this.

sed -e 's/\\r/\r/' < at.txt

But I learned somethere here, also. The external echo command behaves differently from the internal one.

/bin/echo "\r"

Has different output than

echo "\r"

But basically you need a filter to convert the litteral \r string to a single byte 0x0D.