CODEWITHSUNDEEP
macosshellecho
Patrik
Patrik

Reputation: 1

Echo -e on MacOS

I have a problem with script constantly printing signs \n. My script is made for bash and is set to posix=yes. When I ran program on Mac the printing to bash is done only by echo "text here". But when I ran it on Ubuntu VM, then there must be echo -e "text here because, if there's not, then the program does not work correctly.

The problem is, when I try to run script with echo -e in MacOS Bash (not zsh), it will print to terminal -e and call that the is not switcher -e for echo.

Why is it doing, please?

To enter bash in terminal on mac I used command "bash"

Upvotes: -2

Views: 1622

Answers (3)

chepner
chepner

Reputation: 530683

The -e option to bash's built-in echo is a non-POSIX extension that enables processing of backslashed characters according to the XSI extension to the POSIX standard.

POSIX echo is supposed to treat -e as an ordinary argument, not an option. You can see this behavior using /bin/echo, which is POSIX compliant and does not implement the XSI extension.

$ /bin/echo -e foo\\nbar
-e foo\nbar

In bash 3.2, the nonstandard extension -e can be used to enable the XSI extension:

$ /bin/bash -c 'echo -e foo\\nbar'
foo
bar

This can also be enabled using the xpg_echo option:

% /bin/bash -O xpg_echo -c 'echo foo\\nbar'
foo
bar

Turning POSIX mode on make echo POSIX-compliant and enables the XSI extension.

$ /bin/bash --posix  -c 'echo foo\\nbar'
foo
bar
$ /bin/bash --posix  -c 'echo -e foo\\nbar'
-e foo
bar

Now let's jump to bash 5.2. (I'm assuming there are no significant differences between any of the 4.x versions and 5.2; corrections welcome.) Plain echo behaves as in 3.2: no XSI extension and non-compliant with POSIX. xpg_echo also works as before:

$ bash -c 'echo foo\\nbar'
foo\nbar
$ bash -c 'echo -e foo\\nbar'
foo
bar
$ bash -O xpg_echo -c 'echo foo\\nbar'
foo
bar

--posix behaves a little differently, and in my opinion is buggy. In POSIX mode, -e is still recognized as enabling backslash procession, rather than as an ordinary word:

$ bash --posix -c 'echo -e foo\\nbar'
foo
bar

When xpg_echo is enabled, making -e unnecessary, now it is properly treated as an ordinary argument in POSIX mode:

$ bash --posix -O xpg_echo -c 'echo -e foo\\nbar'
-e foo
bar

To avoid these portability issues, use printf instead, which historically did not have as many diverging implementations, and is much more portable in practice than echo.

Upvotes: 2

Mark Reed
Mark Reed

Reputation: 95242

In general you should use printf instead of echo, since it's consistent across shells.

But you must be doing something a bit unusual; out of the box, echo -e works fine in bash on macOS, even in the relatively ancient version 3.2 shipped as /bin/bash:

bash-3.2$ uname -s
Darwin
bash-3.2$ echo -e foo
foo
bash-3.2$ echo -e 'foo\nbar'
foo
bar

Are you perhaps explicitly running the separate program /bin/echo? If so, don't do that; just type the command name echo without the path. That way you get the echo that's built into the shell; if you ask for the separate program by explicit pathname, that's what gets run instead.

Or maybe you're turning on POSIX mode? You said you were starting the shell with bash and not sh, which is the usual way to get POSIX behavior, but you can still explicitly turn on POSIX mode with set -o posix. If you've done that, you'll see the same sort of echo behavior as the /bin version. You can turn that off with set +o posix.

If you want consistency regardless of mode, I recommend switching to printf. It works a little differently, most notably in that it takes a format string followed by the values to fill in, and doesn't automatically append a newline the way echo does; echo "$var" becomes printf '%s\n' "$var". But it is consistent.

Upvotes: 0

Schraubstock1990
Schraubstock1990

Reputation: 144

Try using printf instead of echo.

Support for -e with echo is very shell- and platform-specific, while printf usually just works.

(Bash's builtin command echo support -e, but some other shell's don't)

Example:

printf "%b" "foo\nbar"

Upvotes: 2

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