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End of Options
The options of UNIX(r) utilities usually are introduced with a dash
(-) character.
This is problematic when a non-option argument has to be specified that begins with a dash. A common example for this are filenames.
Many utilities use the convention to specify two consecutive dashes
(--) to signal "end of options at this point". Beyond this tag, no
options are processed anymore, even if an argument begins with a dash.
Example: You want to list (ls) the file with the name -hello. With
common option processing, this could end up in the ls-options -h,
-e, -l and -o and probably in an error message about invalid
options. You use this to avoid the wrong option processing:
ls -- -hello
POSIX(r) specifies that every utility should follow this rule (see ch. 12.2 Utility Syntax Guidelines), except
echo(historical reasons)test(obvious parsing reasons)
See also
- Scripting article, internal: getopts_tutorial