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up vote 3 down vote favorite

What's the meaning of a trailing colon to dash's builtin test (or [) command? I was surprised when I found that if [ ... ]: ; then .. ; fi works (at all) in dash, but not bash, and it seems to be because the builtin's behavior differs from the command's.

$ /usr/bin/\[ 1 ] && echo 1
1
$ /usr/bin/\[ 1 ]: && echo 1
/usr/bin/[: missing `]'
$ [ 1 ]: && echo 1
1
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1  
What does [ 1 ]foo && echo 1 do? My wild initial guess is that dash is checking whether the argument starts with ] instead of whether it's equal to ]. –  godlygeek Mar 26 at 19:07
    
Looks like [ 1 ]foo && echo 1 prints 1, so @Arcege's right. –  David Ehrmann Mar 26 at 19:19

1 Answer 1

up vote 2 down vote accepted

It seems to be more of an issue if parsing the commands. bash expects the closing bracket to be the last argument and complains if it not exactly a "]" string.

bash$ [ 1 ]
bash$ [ 1 ] hi
bash: [: missing `]'
bash$ [ 1 ]hi
bash: [: missing `]'
bash$ dash
$ [ 1 ]
$ [ 1 ] hi
dash: 2: [: missing ]
$ [ 1 hi]
dash: 3: [: missing ]
$ [ 1 ]:
$ [ 1 ]hi
$

The dash shell will just make sure that the first character is "]" and ignore the rest. If the "]" is not in the first character of the last argument, then it returns a similar error as bash.

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