Why doesn't echo -n work in shell on Mac?

The man page for echo says:

 -n    Do not print the trailing newline character.  This may also be

       achieved by appending `c' to the end of the string, as is done by

       iBCS2 compatible systems.  Note that this option as well as the

       effect of `c' are implementation-defined in IEEE Std 1003.1-2001

       (``POSIX.1'') as amended by Cor. 1-2002.  Applications aiming for

       maximum portability are strongly encouraged to use printf(1) to

       suppress the newline character.

However this doesn't seem to work in sh on Mac:

sh-3.2$ echo $0

/bin/sh

sh-3.2$ which echo

/bin/echo

sh-3.2$ echo -n foo

-n foo

It works properly in bash:

bash-3.2$ echo $0

bash

bash-3.2$ which echo

/bin/echo

bash-3.2$ echo -n foo

foobash-3.2

FWIW this only seems to happen on Mac, on Linux it works properly:

$ echo $0

sh

$ echo -n foo

foo$

edited Dec 6 '18 at 13:40

Rob

11.5k82852

asked Nov 21 '18 at 18:39

jjj

400413

If the shell provides a built-in echo, it'll run that instead of /bin/echo – check with type echo instead of which echo to see if it's a built-in.
– Benjamin W.
Nov 21 '18 at 18:41

Ah, thanks. It was confusing because I assumed man echo was pulling up the correct version.
– jjj
Nov 21 '18 at 18:50

Macs are not FreeBSD. Macs are UNIX and OSX though they do contain components of FreeBSD userland.
– Rob
Dec 6 '18 at 13:40

add a comment |

The man page for echo says:

 -n    Do not print the trailing newline character.  This may also be

       achieved by appending `c' to the end of the string, as is done by

       iBCS2 compatible systems.  Note that this option as well as the

       effect of `c' are implementation-defined in IEEE Std 1003.1-2001

       (``POSIX.1'') as amended by Cor. 1-2002.  Applications aiming for

       maximum portability are strongly encouraged to use printf(1) to

       suppress the newline character.

However this doesn't seem to work in sh on Mac:

sh-3.2$ echo $0

/bin/sh

sh-3.2$ which echo

/bin/echo

sh-3.2$ echo -n foo

-n foo

It works properly in bash:

bash-3.2$ echo $0

bash

bash-3.2$ which echo

/bin/echo

bash-3.2$ echo -n foo

foobash-3.2

FWIW this only seems to happen on Mac, on Linux it works properly:

$ echo $0

sh

$ echo -n foo

foo$

edited Dec 6 '18 at 13:40

Rob

11.5k82852

asked Nov 21 '18 at 18:39

jjj

400413

If the shell provides a built-in echo, it'll run that instead of /bin/echo – check with type echo instead of which echo to see if it's a built-in.
– Benjamin W.
Nov 21 '18 at 18:41

Ah, thanks. It was confusing because I assumed man echo was pulling up the correct version.
– jjj
Nov 21 '18 at 18:50

Macs are not FreeBSD. Macs are UNIX and OSX though they do contain components of FreeBSD userland.
– Rob
Dec 6 '18 at 13:40

add a comment |

The man page for echo says:

 -n    Do not print the trailing newline character.  This may also be

       achieved by appending `c' to the end of the string, as is done by

       iBCS2 compatible systems.  Note that this option as well as the

       effect of `c' are implementation-defined in IEEE Std 1003.1-2001

       (``POSIX.1'') as amended by Cor. 1-2002.  Applications aiming for

       maximum portability are strongly encouraged to use printf(1) to

       suppress the newline character.

However this doesn't seem to work in sh on Mac:

sh-3.2$ echo $0

/bin/sh

sh-3.2$ which echo

/bin/echo

sh-3.2$ echo -n foo

-n foo

It works properly in bash:

bash-3.2$ echo $0

bash

bash-3.2$ which echo

/bin/echo

bash-3.2$ echo -n foo

foobash-3.2

FWIW this only seems to happen on Mac, on Linux it works properly:

$ echo $0

sh

$ echo -n foo

foo$

edited Dec 6 '18 at 13:40

Rob

11.5k82852

asked Nov 21 '18 at 18:39

jjj

400413

The man page for echo says:

 -n    Do not print the trailing newline character.  This may also be

       achieved by appending `c' to the end of the string, as is done by

       iBCS2 compatible systems.  Note that this option as well as the

       effect of `c' are implementation-defined in IEEE Std 1003.1-2001

       (``POSIX.1'') as amended by Cor. 1-2002.  Applications aiming for

       maximum portability are strongly encouraged to use printf(1) to

       suppress the newline character.

However this doesn't seem to work in sh on Mac:

sh-3.2$ echo $0

/bin/sh

sh-3.2$ which echo

/bin/echo

sh-3.2$ echo -n foo

-n foo

It works properly in bash:

bash-3.2$ echo $0

bash

bash-3.2$ which echo

/bin/echo

bash-3.2$ echo -n foo

foobash-3.2

FWIW this only seems to happen on Mac, on Linux it works properly:

$ echo $0

sh

$ echo -n foo

foo$

bash macos unix sh

edited Dec 6 '18 at 13:40

Rob

11.5k82852

asked Nov 21 '18 at 18:39

jjj

400413

edited Dec 6 '18 at 13:40

Rob

11.5k82852

asked Nov 21 '18 at 18:39

jjj

400413

edited Dec 6 '18 at 13:40

Rob

11.5k82852

edited Dec 6 '18 at 13:40

Rob

11.5k82852

edited Dec 6 '18 at 13:40

Rob

11.5k82852

asked Nov 21 '18 at 18:39

jjj

400413

asked Nov 21 '18 at 18:39

jjj

400413

asked Nov 21 '18 at 18:39

jjj

400413

If the shell provides a built-in echo, it'll run that instead of /bin/echo – check with type echo instead of which echo to see if it's a built-in.
– Benjamin W.
Nov 21 '18 at 18:41

Ah, thanks. It was confusing because I assumed man echo was pulling up the correct version.
– jjj
Nov 21 '18 at 18:50

Macs are not FreeBSD. Macs are UNIX and OSX though they do contain components of FreeBSD userland.
– Rob
Dec 6 '18 at 13:40

add a comment |

If the shell provides a built-in echo, it'll run that instead of /bin/echo – check with type echo instead of which echo to see if it's a built-in.
– Benjamin W.
Nov 21 '18 at 18:41

Ah, thanks. It was confusing because I assumed man echo was pulling up the correct version.
– jjj
Nov 21 '18 at 18:50

Macs are not FreeBSD. Macs are UNIX and OSX though they do contain components of FreeBSD userland.
– Rob
Dec 6 '18 at 13:40

If the shell provides a built-in echo, it'll run that instead of /bin/echo – check with type echo instead of which echo to see if it's a built-in.
– Benjamin W.
Nov 21 '18 at 18:41

Ah, thanks. It was confusing because I assumed man echo was pulling up the correct version.
– jjj
Nov 21 '18 at 18:50

Macs are not FreeBSD. Macs are UNIX and OSX though they do contain components of FreeBSD userland.
– Rob
Dec 6 '18 at 13:40

add a comment |

1 Answer
1

active

oldest

votes

-n is a bash extension to echo. In version 3.2 (which ships with macOS), bash does not support the extension when invoked as sh. Starting with version 4.0 (some version of which is likely on your Linux box), bash does honor -n when invoked as sh.

Update: the xpg_echo option determines if bash's built-in echo is POSIX-compliant or not. In bash 3.2 (or at least the macOS build of 3.2), this option defaults to on; in bash 4.x, it defaults to off.

% sh -c 'shopt xpg_echo'

xpg_echo        on

% ./sh -c 'shopt xpg_echo'

xpg_echo        off

(./sh is a symlink to /usr/local/bin/bash, a local installation of bash 4.4 on my machine.)

edited Nov 21 '18 at 18:49

answered Nov 21 '18 at 18:43

chepner

245k32232323

1

Doesn't that depend on the xpg_echo option? See item 52 in gnu.org/software/bash/manual/bash.html#Bash-POSIX-Mode
– Benjamin W.
Nov 21 '18 at 18:44

That also comes into play; I'm not sure if it being enabled by default is the difference between 3.2 and 4.x when bash is invoked as sh.
– chepner
Nov 21 '18 at 18:45

According to NEWS, xpg_echo was introduced in 2.04, and its behaviour being affected by POSIX mode was changed in 3.1. Can't find any changes in 3.2 or later, though.
– Benjamin W.
Nov 21 '18 at 18:52

Then why does man sh show -n as a valid option for echo?
– jjj
Nov 21 '18 at 18:53

2

Not really. The best thing to do is simply avoid echo altogether, and use printf, the behavior of which is much more predictable.
– chepner
Nov 21 '18 at 19:07

|
show 9 more comments

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% sh -c 'shopt xpg_echo'

xpg_echo        on

% ./sh -c 'shopt xpg_echo'

xpg_echo        off

(./sh is a symlink to /usr/local/bin/bash, a local installation of bash 4.4 on my machine.)

edited Nov 21 '18 at 18:49

answered Nov 21 '18 at 18:43

chepner

245k32232323

1

Doesn't that depend on the xpg_echo option? See item 52 in gnu.org/software/bash/manual/bash.html#Bash-POSIX-Mode
– Benjamin W.
Nov 21 '18 at 18:44

That also comes into play; I'm not sure if it being enabled by default is the difference between 3.2 and 4.x when bash is invoked as sh.
– chepner
Nov 21 '18 at 18:45

According to NEWS, xpg_echo was introduced in 2.04, and its behaviour being affected by POSIX mode was changed in 3.1. Can't find any changes in 3.2 or later, though.
– Benjamin W.
Nov 21 '18 at 18:52

Then why does man sh show -n as a valid option for echo?
– jjj
Nov 21 '18 at 18:53

2

Not really. The best thing to do is simply avoid echo altogether, and use printf, the behavior of which is much more predictable.
– chepner
Nov 21 '18 at 19:07

|
show 9 more comments

% sh -c 'shopt xpg_echo'

xpg_echo        on

% ./sh -c 'shopt xpg_echo'

xpg_echo        off

(./sh is a symlink to /usr/local/bin/bash, a local installation of bash 4.4 on my machine.)

edited Nov 21 '18 at 18:49

answered Nov 21 '18 at 18:43

chepner

245k32232323

1

Doesn't that depend on the xpg_echo option? See item 52 in gnu.org/software/bash/manual/bash.html#Bash-POSIX-Mode
– Benjamin W.
Nov 21 '18 at 18:44

That also comes into play; I'm not sure if it being enabled by default is the difference between 3.2 and 4.x when bash is invoked as sh.
– chepner
Nov 21 '18 at 18:45

According to NEWS, xpg_echo was introduced in 2.04, and its behaviour being affected by POSIX mode was changed in 3.1. Can't find any changes in 3.2 or later, though.
– Benjamin W.
Nov 21 '18 at 18:52

Then why does man sh show -n as a valid option for echo?
– jjj
Nov 21 '18 at 18:53

2

Not really. The best thing to do is simply avoid echo altogether, and use printf, the behavior of which is much more predictable.
– chepner
Nov 21 '18 at 19:07

|
show 9 more comments

% sh -c 'shopt xpg_echo'

xpg_echo        on

% ./sh -c 'shopt xpg_echo'

xpg_echo        off

(./sh is a symlink to /usr/local/bin/bash, a local installation of bash 4.4 on my machine.)

edited Nov 21 '18 at 18:49

answered Nov 21 '18 at 18:43

chepner

245k32232323

% sh -c 'shopt xpg_echo'

xpg_echo        on

% ./sh -c 'shopt xpg_echo'

xpg_echo        off

(./sh is a symlink to /usr/local/bin/bash, a local installation of bash 4.4 on my machine.)

edited Nov 21 '18 at 18:49

answered Nov 21 '18 at 18:43

chepner

245k32232323

edited Nov 21 '18 at 18:49

answered Nov 21 '18 at 18:43

chepner

245k32232323

answered Nov 21 '18 at 18:43

chepner

245k32232323

answered Nov 21 '18 at 18:43

chepner

245k32232323

1

Doesn't that depend on the xpg_echo option? See item 52 in gnu.org/software/bash/manual/bash.html#Bash-POSIX-Mode
– Benjamin W.
Nov 21 '18 at 18:44

That also comes into play; I'm not sure if it being enabled by default is the difference between 3.2 and 4.x when bash is invoked as sh.
– chepner
Nov 21 '18 at 18:45

According to NEWS, xpg_echo was introduced in 2.04, and its behaviour being affected by POSIX mode was changed in 3.1. Can't find any changes in 3.2 or later, though.
– Benjamin W.
Nov 21 '18 at 18:52

Then why does man sh show -n as a valid option for echo?
– jjj
Nov 21 '18 at 18:53

2

Not really. The best thing to do is simply avoid echo altogether, and use printf, the behavior of which is much more predictable.
– chepner
Nov 21 '18 at 19:07

|
show 9 more comments

1

Doesn't that depend on the xpg_echo option? See item 52 in gnu.org/software/bash/manual/bash.html#Bash-POSIX-Mode
– Benjamin W.
Nov 21 '18 at 18:44

That also comes into play; I'm not sure if it being enabled by default is the difference between 3.2 and 4.x when bash is invoked as sh.
– chepner
Nov 21 '18 at 18:45

According to NEWS, xpg_echo was introduced in 2.04, and its behaviour being affected by POSIX mode was changed in 3.1. Can't find any changes in 3.2 or later, though.
– Benjamin W.
Nov 21 '18 at 18:52

Then why does man sh show -n as a valid option for echo?
– jjj
Nov 21 '18 at 18:53

2

Not really. The best thing to do is simply avoid echo altogether, and use printf, the behavior of which is much more predictable.
– chepner
Nov 21 '18 at 19:07

Doesn't that depend on the xpg_echo option? See item 52 in gnu.org/software/bash/manual/bash.html#Bash-POSIX-Mode
– Benjamin W.
Nov 21 '18 at 18:44

That also comes into play; I'm not sure if it being enabled by default is the difference between 3.2 and 4.x when bash is invoked as sh.
– chepner
Nov 21 '18 at 18:45

According to NEWS, xpg_echo was introduced in 2.04, and its behaviour being affected by POSIX mode was changed in 3.1. Can't find any changes in 3.2 or later, though.
– Benjamin W.
Nov 21 '18 at 18:52

Then why does man sh show -n as a valid option for echo?
– jjj
Nov 21 '18 at 18:53

Not really. The best thing to do is simply avoid echo altogether, and use printf, the behavior of which is much more predictable.
– chepner
Nov 21 '18 at 19:07

|
show 9 more comments

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