81

When I echo $something >> file.txt, a new line will be append to the file.

What if I want to append without a new line?

  • 3
    Be careful doing echo $something, its behavior depends on the IFS variable, and you could end up with disappearing character. You can try the following: var="hello world"; echo $var (two spaces between hello and world) or var="hello world"; IFS='l'; echo $var or var="-e hello \\n world"; echo $var. To solve that, put double quotes around the variable like this: echo "$var", or use printf. – jfg956 Mar 1 '12 at 12:17
96

That's what echo -n is for .

  • 4
    Is there an equivalent for cat? (e.g. when you have a file something.txt rather than a variable $something) – cboettig Nov 19 '13 at 23:05
  • 1
    @cboettig: No. Use a different tool to print everything but the final newline. – Ignacio Vazquez-Abrams Nov 19 '13 at 23:09
  • @cboettig , cat does not add anything to the output by default, so there is no need for a '-n' param for cat. eg, if your file does not have a line-ending in the last line, then your shell prompt will be printed right after the last character of the file and not in a new line – Rondo Jul 18 '17 at 22:53
41

printf is very flexible and more portable than echo. Like the C/Perl/etc implementations, if you do not terminate the format string with \n then no newline is printed:

printf "%s" "$something" >> file.txt
7

If you are using command's output, you can use xargs in combination with echo

/sbin/ip route|awk '/default/ { print $3 }' | xargs echo -n >> /etc/hosts
0

tr is another alternative.

If you're using echo as your input you can get away which tr -d '\n'.

This technique also works when piping in output from other commands (with only a single line of output). Moreover, if you don't know whether the files have UNIX or DOS line endings you can use tr -d '\n\r'.

Here are some tests showing that this works.

Newline included:

something='0123456789' ; echo ${something} | wc -c
11

UNIX newline:

something='0123456789' ; echo ${something} | tr -d '\n\r' | wc -c
10

DOS style:

something='0123456789' ; echo ${something} | unix2dos | tr -d '\n\r' | wc -c
10

Tested with BSD tr and GNU tr.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.