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ZijingWu
ZijingWu

Reputation: 3490

What's "set -- "$progname" "$@"" means in shell script?

I current read this line from our configure.ac build script. I have search on Google for answer but not find it.

I assume it is shell script but what does this means, especially for -- ?

set -- "$progname" "$@"

Upvotes: 7

Views: 10152

Answers (2)

Ramchandra Apte
Ramchandra Apte

Reputation: 4079

From help set:

  --  Assign any remaining arguments to the positional parameters.
      If there are no remaining arguments, the positional parameters
      are unset.

The reason for -- is to ensure that even if "$progname" or "$@" contain dashes, they will not be interpreted as command line options.

set changes the positional parameters, which is stored in $@. So in this case, it appends "$progname" to the beginning of the positional parameters received by the script.

Upvotes: 11

Jon Lin
Jon Lin

Reputation: 143856

The -- is a bash built-in as well as something a lot of unix commands use to denote the end of command options. So if you have something like:

grep -- -v file

the -v won't be interpreted as a grep option, but a parameter (so you can grep for -v).

The $@ is the list of all the parameters that are passed into the script (which I assume the set command is a part of).

The -- ensures that whatever options passed in as part of the script won't get interpreted as options for set, but as options for the command denoted by the $progname variable.

Upvotes: 5

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