Odd BASH behavior. Inline command breaks out of quotes.

I encountered very unexpected behavior when I ran a command a few weeks ago and unfortunately rebooted a server unexpectedly, and I've been unable to determine how an inline command broke out of quotes and was passed to another command, instead of being inside the quoted string. I showed what had happened to a handful of Unix engineers, and the reaction is always, "Oh, that's weird. I dunno."

Below I've included a dumbed down version of what happened. Going one step at a time, the commands make sense, and then you try to pass it as a string to sh -c, and it echos the 1, followed by trying to run the rest of the numbers as commands. Does anyone happen to know how sh -c is interpreting this string as multiple strings it should run? Even if it were multiple strings/lines, sh -c should only run the first parameter as the command. I'm stumped.

I've included the strace output of running the command that produces the weird behavior. I'm not very good at reading that output, unless it's super obvious. I think it may have something to do with how it's interpreting \n in the first line of strace.

Anyone out there who happens to know what causes this behavior?

Strace: http://pastebin.com/Ehn80GqN

[user@server ~]$ cat testfile 1 2 3 4 5 6 7 8 9 10 [user@server ~]$ echo $(cat testfile) 1 2 3 4 5 6 7 8 9 10 [user@server ~]$ sh -c "echo 1 2 3 4 5 6 7 8 9 10" 1 2 3 4 5 6 7 8 9 10 [user@server ~]$ sh -c "echo $(cat testfile)" 1 sh: line 1: 2: command not found sh: line 2: 3: command not found sh: line 3: 4: command not found sh: line 4: 5: command not found sh: line 5: 6: command not found sh: line 6: 7: command not found sh: line 7: 8: command not found sh: line 8: 9: command not found sh: line 9: 10: command not found [user@server ~]$ sh -c "echo \$(cat testfile)" 1 2 3 4 5 6 7 8 9 10 [user@server ~]$ sh --version GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu) Copyright (C) 2005 Free Software Foundation, Inc. [user@server ~]$ cat /etc/redhat-release Red Hat Enterprise Linux Server release 5.11 (Tikanga)