Why does cd print when run in command substitution?

Posted by reasgt on Super User See other posts from Super User or by reasgt
Published on 2012-08-29T19:39:07Z Indexed on 2012/08/30 3:40 UTC
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Filed under:

bash

|

less

|

cd

If I use the 'cd' BASH built-in in a command substitution, it prints extra stuff to stdout, but only when piped to, eg., less.

$ echo `cd .`

# The output is a single newline, appended by echo.


$ echo `cd .` | less
# less displays:
ESC]2;my.hostname.com - tmp/testenv^G
(END)

What's going on there? This behavior isn't documented in the bash man page for cd. Obviously, running just 'cd' in a command substitution is silly, but something like

NEWDIR=`cd mypath; pwd`

could be useful.

I solved this by instead using

NEWVAR=`cd mypath > /dev/null 2>&1; pwd`

but I still want to know what's going on.

Bash Version: GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu) Copyright (C) 2005 Free Software Foundation, Inc.

Distro: Scientific Linux SL release 5.5 (Boron)

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