p is searching stdin.
.sp
When searching over sets of files that may require one of several
preprocessors, \fICOMMAND\fP should be a wrapper program which first classifies
\fIPATH\fP based on magic numbers/content or based on the \fIPATH\fP name and
then dispatches to an appropriate preprocessor. Each \fICOMMAND\fP also has its
standard input connected to \fIPATH\fP for convenience.
.sp
For example, a shell script for \fICOMMAND\fP might look like:
.sp
.EX
    case "$1" in
    *.pdf)
        exec pdftotext "$1" -
        ;;
    *)
        case $(file "$1") in
        *Zstandard*)
            exec pzstd -cdq
            ;;
        *)
            exec cat
            ;;
        esac
        ;;
    esac
.EE
.sp
The above script uses \fBpdftotext\fP to convert a PDF file to plain text. For
all other files, the script uses the \fBfile\fP utility to sniff the type of
the file based on its contents. If it is a compressed file in the Zstandard
format, then \fBpzstd\fP is used to decompress the contents to stdout.
.sp
This overrides the \flag{search-zip} flag.
there is no affirmative switch for --pre