Advanced UNIX Programming

Arguments That Look Like Options

You may have encountered a situation in which you wanted to specify an argument that started with a hyphen, and your command complained about the improper options that were being used. For example, if grep(1) were used to search a source program for the string --help, you might experience the following under FreeBSD:

$ grep --help tempnam.c
grep: illegal option -- -
usage: grep [-[AB] <num>] [-CEFGLVXHPRSZabchilnqsvwxy]
       [-e <expr>] [-f file] [files ...]
$

The problem with this grep(1) command is that the command was confused about how to treat the text --help. The following technique shows how to avoid this little problem:

$ grep -- --help tempnam.c
$

The example shows that grep(1) understood the -- (double ...