End of Options

The options of UNIX® 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 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® specifies that every utility should follow this rule ("utility syntax guidelines"), except

• echo (historical reasons)
• test (obvious parsing reasons)

• Scripting article, internal: Small getopts tutorial