Subject: Re: bug#34126: grep v. 3.1 – unexpected error message "grep: i.: No such file or directory"

From: Eric Blake <[email-masked]>
Date: Fri, 18 Jan 2019 14:37:30 -0600

tag 34126 notabug
thanks

On 1/18/19 2:27 PM, Ricky Tigg wrote:
> OS: *Fedora*; Component: grep.x86_64  3.1-8.fc29
> 
> Commands executed:
> 
> $ dnf list|grep -Ei langpack | grep fi.
> glibc-langpack-fi.x86_64            2.28-26.fc29         @updates
> langpacks-fi.noarch                 1.0-13.fc29          @System
> (...)
> 
> $ dnf list|grep -Ei langpack | grep fi. | grep "-fi."
> grep: i.: No such file or directory
> 
> Using grep twice in the same command, the command's last grep is expected
> to produce targets, not an STDERR. Probably an issue.

Not an issue in grep, but in your attempt to use a pattern beginning
with - in a way that grep cannot distinguish from options.  That is, you
asked grep to use the -f option, which takes an argument, so it used
"i." as the argument for -f, and failed because there is no file named
'i.' in your current directory.  (That's true whether you write -fi. or
"-fi.", because the shell strips quoting before grep sees its argv[]).

You want to use either of these formulations instead:

grep -e -fi.
grep -- -fi.

where the "-e" option says to treat the next argv[] entry as a pattern,
even if it otherwise would look like an option, and then continue
finding further options; while the "--" argument says that no more
options are present, and that all further command line arguments are
treated according to their traditional positional usage).  The
difference becomes apparent in constructs like:

grep -e -fi. -i     # greps stdin case-insensitively for "-fi."
grep -- -fi. -i     # greps file ./-i case-sensitively for "-fi."

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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