source: vendor/bash/3.1-p17/examples/scripts.v2/pf

#! /bin/bash
#
# original from:
#
# @(#) p.ksh 1.1 93/11/09
# p: page compressed & plain files in the order given 
# 92/01/23 john h. dubois iii (john@armory.com)
# 92/02/14 changed incorrect zpack to pcat
# 92/02/16 added help
# 92/10/11 search for file.Z and file.z if file not found
# 92/10/18 pass options to pager
# 93/11/09 Understand gzipped files too
#          Wait after printing message about unreadable files
#          Make less prompt include name of file being uncompressed
#
# conversion to bash v2 by Chet Ramey; renamed to pf
#
DefPager=/local/bin/less

istrue()
{
        test 0 -ne "$1"
}

warn()
{
        echo "$@" 1>&2
}

if [ "$1" = -h ]; then
    echo \
"$0: page a file.
Usage: $0 [pager-option ...] [filename ...]
Files are paged by the program specified in the user's PAGER
environment variable, or by $DefPager if PAGER is not set.
If no filename is given, text to page is read from the standard input.
If filenames are given, they are either paged directly, or unpacked/
uncompressed and then paged.  Files are assumed to be in packed, compressed,
or gzipped format if the filename ends in .Z, .z, or .gz respectively.
If a filename that does not end in .Z, .z, or .gz is not found, it is
searched for with one of those extensions attached.
Each group of plain files is paged by a single instance of the pager.
Each packed or compressed file is paged by a separate instance of the
pager. 
Initial arguments beginning with + or - are taken to be pager options and
are passed to each instance of the pager.  
If a pager option takes a value it should be given with the option as a
single argument (with no space between the option and the value)."
    exit 0
fi

# Get pager options
while [ $# -gt 0 ]; do
    case "$1" in
    -*|+*)      Opts="$Opts $1" ; shift;;
    *)  break;;
    esac
done

[ -z "$PAGER" ] && PAGER=$DefPager

# Read from stdin
[ $# = 0 ] && exec $PAGER $Opts

typeset -i filenum=0 badfile=0

for file; do
    if [ ! -r "$file" ]; then
        case "$file" in
        *.[Zz]|*.gz)
                # Check if user specified a compressed file without giving its extension
                for ext in Z z gz; do
                    if [ -r "$file.$ext" ]; then
                        file="$file.$ext"
                        break
                    fi
                done;;
        esac
    fi
    if [ ! -r "$file" ]; then
        warn "$file: cannot read."
        badfile=1
    else
        files[filenum]=$file
        let filenum+=1
    fi
done

if istrue $badfile && [ $filenum -gt 0 ]; then
    echo -n "Press return to continue..." 1>&2
    read
fi

unset plain

for file in "${files[@]}"; do
    case "$file" in
    *.[zZ]|*.gz)
        set -- Z zcat z pcat gz gzcat
        # Find correct uncompression program
        while [ $# -gt 0 ]; do
            case "$file" in
            *.$1)
                # Page any uncompressed files so that they will be read
                # in the correct order
                [ ${#plain[@]} -gt 0 ] && $PAGER $Opts "${plain[@]}"
                unset plain[*]
                # If page is less, set the prompt to include the name of
                # the file being uncompressed.  Escape the . in the extension
                # because less treats is specially in prompts (other dots
                # in filenames will still be mucked with).
                case "$PAGER" in
                *less)  Prompt="-P[${file%.$1}\\.$1] (%pb\\%)" ;;
                *)      unset Prompt ;;
                esac
                $2 "$file" | $PAGER "$Prompt" $Opts
                break
            esac
            shift 2
        done
        ;;
    *)  plain[${#plain[@]}]=$file;;
    esac
done

# Page any uncompressed files that haven't been paged yet
[ ${#plain[@]} -gt 0 ] && exec $PAGER $Opts "${plain[@]}"