eless – A Better less

echo "This script is not supposed to send output to a pipe"
exit 1

debug "Pipe Contents (up to 10 lines) : \`$(head -n 10 "${piped_data_file}")'"
# Remove blank lines from $piped_data_file. Some or all of BSD man
# pages would have a blank line at the top.
# -- https://github.com/kaushalmodi/eless/issues/27#issuecomment-365992910.
# GNU ls man page begins with:
#   l1: LS(1)                            User Commands                           LS(1)
# BSD ls man page begins with:
#   l1:
#   l2: LS(1)                     BSD General Commands Manual                    LS(1)
perl -ne 'print unless /^\s*$/' "${piped_data_file}" > "${piped_data_file}.noblank"

# Now parse only the first line of that ${piped_data_file}.noblank file.
first_line_piped_data=$(head -n 1 "${piped_data_file}.noblank")
debug "first_line_piped_data = \`${first_line_piped_data}'"

# It is not mandatory for the below perl regex to always match. So OR it with
# "true" so that "set -e" does not kill the script at this point.

# The first line of man pages is assumed to be
#   FOO(1)  optional something something FOO(1)
# For some odd reason, the "BASH_BUILTINS" man page is named just
# "builtins"; below deals with that corner case.
# .. faced this problem when trying to do "man read | eless".
#   If the man page name is completely in upper-case, convert it
# to lower-case.
man_page=$(echo "${first_line_piped_data}" \
               | perl -ne '/^([A-Za-z0-9-_]+\([a-z0-9]+\))(?=\s+.*?\1$)/ and print $1' \
               | perl -pe 's/bash_builtins/builtins/i' \
               | perl -pe 's/xsel\(1x\)/xsel/i' \
               | perl -pe 's/^[A-Z0-9-_()]+$/\L$_/' \
               || true)
# Using perl expression above instead of below grep (which requires
# GNU grep -- not available by default on macOS):
#   grep -Po '^([A-Za-z-_]+\([0-9]+\))(?=\s+.*?\1$)'
debug "man_page 1 = \`${man_page}'"

# If it's not a regular man page, check if it's a Perl man page.
if [[ -z ${man_page} ]]
then
    # The first line of Perl man pages is assumed to be
    #   Foo::Bar(1zoo) something something Foo::Bar(1zoo)
    # Example: PAGER=eless man Net::FTP  or  PAGER=less man Net::FTP | eless
    #   If the man page name is completely in upper-case, convert it
    # to lower-case.
    # Example: PAGER=eless man error::pass1  or  PAGER=less man error::pass1 | eless
    man_page=$(echo "${first_line_piped_data}" \
                   | perl -ne '/^([A-Za-z0-9-_]+::[A-Za-z0-9-_]+)(\([a-z0-9]+\))(?=\s+.*?\1\2$)/ and print $1' \
                   | perl -pe 's/^[A-Z0-9-_]+::[A-Z0-9-_]+$/\L$_/' \
                   || true)
    debug "man_page 2 = \`${man_page}'"
fi

# The first line of Python package MODULE help is assumed to be
#   "Help on package MODULE:" OR "Help on module MODULE:" OR "Help on SOMETHING in module MODULE:"
# Examples: PAGER=eless python3; help('shlex') ->  "Help on module shlex:"
#           PAGER=eless python3; help('iter')  ->  "Help on built-in function iter in module builtins:"
#           PAGER=eless python3; help('exit')  ->  "Help on Quitter in module _sitebuiltins object:"
python_module_help=$(echo "${first_line_piped_data}" \
                         | perl -ne '/^Help on (?:.+ in )*(?:module|package) (.*)(?=:$)/ and print $1' \
                         || true)
# Using perl expression above instead of below grep (which requires
# GNU grep -- not available by default on macOS):
#   grep -Po '^Help on (.+ in )*(module|package) \K(.*)(?=:$)'
debug "python_module_help = \`${python_module_help}'"

# The first line of Info manuals will usually be the below:
#   - Begin with "File:", and
#   - Contain "Node:"
# Example: "File: emacs,  Node: Top,  Next: Distrib,  Prev: (dir),  Up: (dir)" -> "emacs"
info_man=$(echo "${first_line_piped_data}" \
               | perl -ne '/^File: ([^.,]+)(\.info.*)*.*,  Node.*/ and print $1' \
               || true)
debug "info_man 1 = \`${info_man}'"

# If an Info manual is not detected by the above regex, try the below regex.
if [[ -z ${info_man} ]]
then
    # The first line of Info manuals could be something like:
    #   /path/to/some.info or /path/to/some.info.gz
    # Example: "/home/kmodi/usr_local/apps/6/emacs/26/share/info/emacs.info.gz" -> "emacs"
    info_man=$(echo "${first_line_piped_data}" \
                   | perl -ne '/^(?:.*\/)*([^\/]+)(?=\.info(?:\-[0-9]+)*(?:\.gz)*$)/ and print $1' \
                   || true)
    # Using perl expression above instead of below grep (which requires
    # GNU grep -- not available by default on macOS):
    #   grep -Po '^(.*/)*\K[^/]+(?=\.info(\-[0-9]+)*(\.gz)*$)'
    debug "info_man 2 = \`${info_man}'"
fi

if [[ -n ${man_page} ]]
then
    <<man-page>>
elif [[ -n ${python_module_help} ]]
then
    <<python-module-help>>
elif [[ -n ${info_man} ]]
then
    <<info-manual>>
else # No man page or info manual detected
    <<neither-man-nor-info>>
fi

cmd="emacs_Q_view_mode ${emacs_args[*]}"

(when (getenv "ELESS_DEBUG")
  (setq debug-on-error t))

;; Keep the default-directory to be the same from where
;; this script was launched from; useful during C-x C-f
(setq default-directory "'"$(pwd)"'/")

;; No clutter
(menu-bar-mode -1)
(if (fboundp (function tool-bar-mode)) (tool-bar-mode -1))

;; Show line and column numbers in the mode-line
(line-number-mode 1)
(column-number-mode 1)

(setq-default indent-tabs-mode nil) ;Use spaces instead of tabs for indentation
(setq x-select-enable-clipboard t)
(setq x-select-enable-primary t)
(setq save-interprogram-paste-before-kill t)
(setq require-final-newline t)
(setq visible-bell t)
(setq load-prefer-newer t)
(setq ediff-window-setup-function (function ediff-setup-windows-plain))

(setq org-src-fontify-natively t)       ;Syntax-highlight source blocks in org

(fset (quote yes-or-no-p) (quote y-or-n-p)) ;Use y or n instead of yes or no

(setq ido-save-directory-list-file nil) ;Do not save ido history
(ido-mode 1)
(setq ido-enable-flex-matching t)       ;Enable fuzzy search
(setq ido-everywhere t)
(setq ido-create-new-buffer (quote always)) ;Create a new buffer if no buffer matches substringv
(setq ido-use-filename-at-point (quote guess)) ;Find file at point using ido
(add-to-list (quote ido-ignore-buffers) "*Messages*")

(setq isearch-allow-scroll t) ;Allow scrolling using isearch
;; DEL during isearch should edit the search string, not jump back to the previous result.
(define-key isearch-mode-map [remap isearch-delete-char] (function isearch-del-char))

;; Truncate long lines by default
(setq truncate-partial-width-windows nil) ;Respect the value of truncate-lines
(toggle-truncate-lines +1)

(global-hl-line-mode 1)

(cond
 ((derived-mode-p (quote dired-mode)) (eless/dired-mode-customization))
 ((derived-mode-p (quote Man-mode)) (eless/Man-mode-customization))
 ((derived-mode-p (quote Info-mode)) (eless/Info-mode-customization))
 ((derived-mode-p (quote tar-mode)) (eless/tar-mode-customization))
 (t     ;Enable view-mode if none of the above major-modes are active
  ;; Auto-enable diff-mode. For example, when doing "diff foo bar | eless"
  (eless/enable-diff-mode-maybe)
  ;; Auto-convert ANSI codes to colors. For example, when doing "ls --color=always | eless"
  (eless/enable-ansi-color-maybe)
  (view-mode 1)))

(eval-after-load (quote view)
  (quote
   (progn
     (define-key view-mode-map (kbd "!") (function eless/delete-matching-lines))
     (define-key view-mode-map (kbd "&") (function eless/keep-lines))
     (define-key view-mode-map (kbd "0") (function delete-window))
     (define-key view-mode-map (kbd "1") (function delete-other-windows))
     (define-key view-mode-map (kbd "A") (function auto-revert-tail-mode))
     (define-key view-mode-map (kbd "D") (function dired))
     (define-key view-mode-map (kbd "N") (function next-error)) ;Next line in *occur*
     (define-key view-mode-map (kbd "P") (function previous-error)) ;Previous line in *occur*
     (define-key view-mode-map (kbd "K") (function eless/delete-matching-lines))
     (define-key view-mode-map (kbd "a") (function auto-revert-mode))
     (define-key view-mode-map (kbd "g") (function eless/revert-buffer-retain-view-mode))
     (define-key view-mode-map (kbd "k") (function eless/keep-lines))
     (define-key view-mode-map (kbd "n") (function next-line))
     (define-key view-mode-map (kbd "o") (function occur))
     (define-key view-mode-map (kbd "p") (function previous-line))
     (define-key view-mode-map (kbd "q") (function eless/kill-emacs-or-buffer))
     (define-key view-mode-map (kbd "t") (function toggle-truncate-lines)))))

;; Global custom bindings
(global-set-key (kbd "M-/") (function hippie-expand))
(global-set-key (kbd "C-x C-b") (function ibuffer))
(global-set-key (kbd "C-x C-c") (function eless/save-buffers-maybe-and-kill-emacs))
(global-set-key (kbd "C-x C-f") (function view-file))
(global-set-key (kbd "C-c q") (function query-replace-regexp))
(global-set-key (kbd "<f5>") (function eless/revert-buffer-retain-view-mode))

(when (display-graphic-p)
  (eval-after-load (quote view)
    (quote
     (progn
       (define-key view-mode-map (kbd "+") (function text-scale-adjust))
       (define-key view-mode-map (kbd "-") (function text-scale-adjust))
       (define-key view-mode-map (kbd "=") (function text-scale-adjust)))))
  (global-set-key (kbd "C-<right>") (function eless/frame-width-double))
  (global-set-key (kbd "C-<left>") (function eless/frame-width-half))
  (global-set-key (kbd "C-<down>") (function eless/frame-height-double))
  (global-set-key (kbd "C-<up>") (function eless/frame-height-half)))

(let* ((cfg-file "elesscfg")
       (cfg-path (if (fboundp (quote locate-user-emacs-file))
                     (locate-user-emacs-file cfg-file)
                   ;; For emacs older than 23.1.
                   (let ((home (file-name-as-directory (getenv "HOME"))))
                     (or (expand-file-name cfg-file (concat home ".emacs.d"))
                         (expand-file-name cfg-file home))))))
  (unless (load cfg-path :noerror)
    (load-theme (quote tango-dark) :no-confirm)
    ;; The tango-dark theme is good except for the bright yellow hl-line face
    (custom-theme-set-faces
     (quote user)
     (quote (hl-line ((t (:background "color-238")))))
     (quote (Man-overstrike ((t (:foreground "#f3dc55" :weight normal)))))))) ;gold yellow

git clone https://github.com/kaushalmodi/eless

make eless

make doc

make all