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How do I use filenames that start with a dash "-" as command arguments?

rated 0 times [ 22] [ 0] / answers: 1 / hits: 1173 / 3 Years ago, wed, july 7, 2021, 10:12:53

This may be a simple question, but how do I use files starting with "-" with command line programs?

For example, I am trying to use pdfgrep on a file named -2013-01-01.pdf but it complains that there are no options defined for 2, 0, 1, 3 and so on.

Changing the filename to something that does not start with "-" solves it, but this is not an option since the files aren't created by me. I simply want to check for a specific change I know is coming.

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3 Years ago

answered 3 Years ago izecaptur · Accepted Answer

Very frequently -- is used on the command-line to signal to a program that no more available command switches are going to be used. This is particularly useful if a file contains a dash, which the program would try to interpret as an option.

Without the --, there is an error generated:

$ pdfgrep -i posix -find.pdf -xorg.pdf



pdfgrep: invalid option -- 'f'

pdfgrep: invalid option -- 'd'

pdfgrep: invalid option -- '.'

pdfgrep: invalid option -- 'p'

pdfgrep: invalid option -- 'd'

pdfgrep: invalid option -- 'f'

With the -- used we have a successful command:

$ pdfgrep -i posix -- -find.pdf -xorg.pdf



-find.pdf: on the command line. Currently-implemented types are emacs (this is the default), posix-awk,

-find.pdf: posix-basic, posix-egrep and posix-extended.

-find.pdf: posix-basic, posix-egrep and posix-extended.

-find.pdf: posix-basic, posix-egrep and posix-extended.

pdfgrep is programmed to understand -- to mean that the following command-line arguments are not options. Most programs do the same, but not all programs understand --. For programs that don't, the solution is to prepend the filename with ./, like this:
```
 pdfgrep -i posix ./-find.pdf ./-xorg.pdf
```
This should work with any command, unless for some reason the command cannot accept a path, only a pure filename.

For a general introduction to the command-line, see this useful PDF.