Pipe into a browser, or a previewer like Quick Look (macOS and Linux)

browser

#!/usr/bin/env bash
##
##  pipe into a browser or a previewer like Quick Look on Mac or Linux
##
##  Authors:   Kevin Ernst <ernstki -at- mail.uc.edu>
##             Geoff Nixon <geoff -at- geoffnixon.net>
##  Date:      24 September 2022
##  See also:  https://gist.github.com/defunkt/318247#gistcomment-1196817
##

# terminate on errors, unset variables are errors
set -eu
# set TRACE=1 in the environment to trace execution
TRACE=${TRACE:-}
(( TRACE )) && set -x

ME=${0##*/}
HOMEPAGE='https://gist.github.com/ernstki/0c5979dfd60d68c483772d1d98c3e810'
SYSTEM=$(uname -s)
# how long to sleep in seconds before removing the temp file
CLEANUPDELAY=5
# what to use if the '-q' / '--quick' option is given
PREVIEWER='sushi'
# what to use if BROWSER isn't defined in the environment
OPENER='xdg-open'

if [[ $SYSTEM == Darwin ]]; then
    PREVIEWER='qlmanage -p'; OPENER='open'
fi

if [[ -t 1 ]]; then
    # use colors if stdout is a terminal
    BOLD=$(tput bold)
    UL=$(tput sgr 0 1)
    RED=$(tput setaf 1)
    CYAN=$(tput setaf 6)
    RESET=$(tput sgr0)
    ERROR="$BOLD${RED}ERROR$RESET"
    NOTE="$BOLD${CYAN}NOTE$RESET"
else
    BOLD=;UL=;RED=;RESET=;ERROR='ERROR'
fi

USAGE="
  $BOLD$ME$RESET - open stdout (or a file) in a browser or previewer

    ${UL}usage$RESET
      $ME [-h|--help]
      $ME [-q|--quick] FILE [FILE...]
      some-other-command | $ME [-q|--quick]

    ${UL}where$RESET
      -h, --help       prints this help
      -q, --quick      uses previewer ($PREVIEWER) instead of default browser
      -s, --stay-open  stays open and retains the temp file until a key is
                       pressed; useful when 'browser' is used in a pipe
      -k, --keep       retains the temp file after exit

    ${UL}homepage$RESET
      $HOMEPAGE
"

# respect BROWSER if set
opener=${BROWSER:-$OPENER}
inputs=()

# print line number if 'set -e' causes the script to terminate prematurely
trap 'echo -e "\n$ERROR: Script error at $BASH_SOURCE line #$LINENO.\n" >&2' ERR

# default to preview behavior if called as 'ql<something>'
if [[ $ME =~ ^ql ]]; then
    set -- --quick "$@"
fi

stay=
keep=

while (( $# )); do
    case $1 in
        -h|--help)
            echo "$USAGE"
            exit
            ;;
        -q|--quick)
            if [[ $(type -t ${PREVIEWER%% *}) ]]; then
                opener=$PREVIEWER
            else
                echo -e "\n$ERROR: No previewer found; see PREVIEWER in $BASH_SOURCE.\n" >&2
                exit 1
            fi
            ;;
        -s|--stay*)
            stay=1
            ;;
        -k|--keep)
            keep=1
            ;;
        -*)
            echo -e "\n$ERROR: Unsupported option '$1'. See '--help'.\n" >&2
            exit 1
            ;;
        *)
            inputs+=("$1")
            ;;
    esac
    shift
done


if [[ ${#inputs[@]} -eq 0 ]]; then
    if [[ -t 0 ]]; then
        echo -e "$ERROR: At least one file argument is required."
        echo "$USAGE" >&2
        exit 1
    fi
    # otherwise, use stdin
    inputs=('-')
fi

for input in "${inputs[@]}"; do
    # FIXME: how to make this work for process substitutions?
    if [[ -r $input && ( -f $input || -L $input ) ]]; then
        # don't create an extra temp file if the file *is* a file
        if (( stay )); then
            echo "$NOTE: '--stay-open' is only useful in a pipe. See '--help'." >&2
        fi
        if (( TRACE )); then
            $opener "$input"
        else
            # suppress stdout and stderr by default; 'qlmanage' on macOS is
            # quite chatty, for example
            $opener "$input" &>/dev/null
        fi
    else
        # macOS/BSD `mktemp` doesn't support a suffix, so this rigmarole
        tmp=$(mktemp "${TMPDIR:=/tmp}/$ME-XXXXXXXX")
        mv "$tmp"{,.html}; tmp="$tmp.html"
        if (( !keep )); then
            trap "(sleep $CLEANUPDELAY; rm '$tmp')&" EXIT
        fi
        umask 077  # protect temp file from prying eyes
        cat "$input" > "$tmp"
        if (( TRACE )); then
            $opener "$tmp"
        else
            $opener "$tmp" &>/dev/null
        fi
        if (( stay )); then
            if (( keep )); then
                echo "$NOTE: '--stay-open' serves no purpose when used with '--keep'. See '--help'." >&2
            fi
            # FIXME: does '</dev/tty' work on macOS/BSD, too?
            read -s -N1 -p$'Press a key to continue...\n' < /dev/tty
        fi
    fi
done

This is a very useful script! Thanks! One issue I encountered was on my Mac (M2 Ventura 13.4). The base64 command now seems to require explicit -i for input and -o for output.

@brian-lc The more I stared at it, the more puzzled I became about why the original author did that instead of just using mktemp. Do you have any insights?

Anyway, I removed all the base64 stuff entirely to avoid the problem. If the updated version still works in your testing (I'm still using some old busted version of macOS), then I think we can put this one to rest.