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Post Closed as "exact duplicate" by Stéphane Chazelas, Gilles 'SO- stop being evil', manatwork, nopcorn, kjo
Added the excerpt from the man page being referenced
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edit approved Mar 7, 2013 at 13:43
Michael Hampton
edit approved Mar 7, 2013 at 13:43
Michael Hampton
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The zsh man page, in its section on test (aka [), explicitly advises against using it at all, and urges readers to use [[ whenever possible.

The relevant section states:

The command attempts to implement POSIX and its extensions where these are specified. Unfortunately there are intrinsic ambiguities in the syntax; in particular there is no distinction between test operators and strings that resemble them. The standard attempts to resolve these for small numbers of arguments (up to four); for five or more arguments compatibility cannot be relied on. Users are urged wherever possible to use the '[[' test syntax which does not have these ambiguities.

I think I've come across similar advice for bash, but as I scan over the bash man page I can't find any "official" recommendation there on which form ([ or [[) to use. (Maybe I missed it?)

Is there any reason, other than backward compatibility with "older shells", for using [ in a bash script? Or to put it differently, does bash keep [ along with [[ for reasons other than backward compatibility?

The zsh man page, in its section on test (aka [), explicitly advises against using it at all, and urges readers to use [[ whenever possible.

I think I've come across similar advice for bash, but as I scan over the bash man page I can't find any "official" recommendation there on which form ([ or [[) to use. (Maybe I missed it?)

Is there any reason, other than backward compatibility with "older shells", for using [ in a bash script? Or to put it differently, does bash keep [ along with [[ for reasons other than backward compatibility?

The zsh man page, in its section on test (aka [), explicitly advises against using it at all, and urges readers to use [[ whenever possible.

The relevant section states:

The command attempts to implement POSIX and its extensions where these are specified. Unfortunately there are intrinsic ambiguities in the syntax; in particular there is no distinction between test operators and strings that resemble them. The standard attempts to resolve these for small numbers of arguments (up to four); for five or more arguments compatibility cannot be relied on. Users are urged wherever possible to use the '[[' test syntax which does not have these ambiguities.

I think I've come across similar advice for bash, but as I scan over the bash man page I can't find any "official" recommendation there on which form ([ or [[) to use. (Maybe I missed it?)

Is there any reason, other than backward compatibility with "older shells", for using [ in a bash script? Or to put it differently, does bash keep [ along with [[ for reasons other than backward compatibility?

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kjo
kjo
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[ vs [[ : which one to use in bash scripts?

The zsh man page, in its section on test (aka [), explicitly advises against using it at all, and urges readers to use [[ whenever possible.

I think I've come across similar advice for bash, but as I scan over the bash man page I can't find any "official" recommendation there on which form ([ or [[) to use. (Maybe I missed it?)

Is there any reason, other than backward compatibility with "older shells", for using [ in a bash script? Or to put it differently, does bash keep [ along with [[ for reasons other than backward compatibility?