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The name of the file is '[' . When I open it up in vi it looks like it's a copy of 'test'. It's owned by root.

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What's the output of stat /bin/[? – SirCharlo Aug 23 '12 at 20:02
@SirCharlo File: `/usr/bin/[' Size: 30244 Blocks: 64 IO Block: 4096 regular file Device: 805h/2053d Inode: 2499684 Links: 1 Access: (0755/-rwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2012-08-23 14:50:24.545242581 -0400 Modify: 2011-02-23 08:22:21.000000000 -0500 Change: 2012-07-09 22:31:52.133720601 -0400 – Josh Aug 23 '12 at 20:08
up vote 8 down vote accepted

That file is supposed to be there (or under /usr/bin/[). It allows you to type, for instance, [ -f $HOME/.bashrc ] && echo ".bashrc exists", which is equivalent to test -f $HOME/.bashrc && echo ".bashrc exists".

Reality is a bit more complicated, since bash overrides /usr/bin/[ with its own [, so you can use the [ executable by providing a full path, /usr/bin/[ -f $HOME/.bashrc ] && echo ".bashrc exists".

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I'm curious now. I don't have that file.. – SirCharlo Aug 23 '12 at 20:07
Try /usr/bin/[. – pablomme Aug 23 '12 at 20:10
@pablomme Thanks! – Josh Aug 23 '12 at 20:21
@pablomme You're the man! – SirCharlo Aug 23 '12 at 20:28

It is a version of test that requires a ] as last argument. It's often used in shell scripts, like in

if [ -e some_file ]; then ...

(but in most modern shell, like Bash, it's a builtin command).

It's required by POSIX

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