Half-unfuck Debian's 'crontab -e' when $EDITOR is emacsclient

~__bin__crontab

#!/bin/bash -                                                                                                                          
# SPDX-FileCopyrightText: <text> © 2020 Alan D. Salewski <ads@salewski.email> </text>                                                  
#                                                                                                                                      
# SPDX-License-Identifier: GPL-2.0-or-later                                                                                            
                                                                                                                                       
# This file has been saved as a GitHub Gist here:                                                                                      
#                                                                                                                                      
#     https://gist.github.com/salewski/b33ce69a7d8c74587545d5bb65cfd4a4                                                                
                                                                                                                                       
# crontab: Wraps Debian's busted crontab(1) command to half-unfuck                                                                     
# 'crontab -e' invocation when $EDITOR is set to some variation of                                                                     
# 'emacsclient'.                                                                                                                       
#                                                                                                                                      
# See:                                                                                                                                 
#     • "Debian Bug #19237: crontab should support TMPDIR env variable"                                                                
#       https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=19237                                                                        
#                                                                                                                                      
# For now, our workaround is to first try to guess the path to the "Unix                                                               
# domain socket" that the 'crontab' command is effectively hiding from                                                                 
# 'emacsclient'. If that doesn't work, then we just intercept the                                                                      
# 'crontab' invocation and manually set EDITOR to 'vim'  :-(                                                                           
#                                                                                                                                      
# Whether you are running Emacs in "daemon mode" (that is, you started                                                                 
# emacs with some variation of 'emacs --daemon') or you just ran                                                                       
# (server-start) in your running emacs, generally speaking you /ought                                                                  
# to/ be able (without this workaround) to invoke 'emacsclient' and have                                                               
# it connect to your existing session. Alas...                                                                                         
#                                                                                                                                      
#                                                                                                                                      
# Here's what the bug looks like in action:                                                                                            
#                                                                                                                                      
#     $ EDITOR='emacsclient -t' crontab -e                                                                                             
#     emacsclient: can't find socket; have you started the server?                                                                     
#     To start the server in Emacs, type "M-x server-start".                                                                           
#     emacsclient: No socket or alternate editor.  Please use:                                                                         
#                                                                                                                                      
#             --socket-name                                                                                                            
#             --server-file      (or environment variable EMACS_SERVER_FILE)                                                           
#             --alternate-editor (or environment variable ALTERNATE_EDITOR)                                                            
#     crontab: "emacsclient -t" exited with status 1                                                                                   
                                                                                                                                       
set -e                                                                                                                                 
                                                                                                                                       
declare -r PROG='crontab (wrapper)'                                                                                                    
                                                                                                                                       
declare -r CRONTAB_PROG='/usr/bin/crontab'                                                                                             
                                                                                                                                       
printf "${PROG} (warn): wrapped crontab command (%s) to workaround Debian bug #19237 (\"crontab should support TMPDIR env variable\")\$
'    See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=19237\n\n' \                                                               
       "$(readlink -f "$0")" 1>&2                                                                                                      
                                                                                                                                       
set -x                                                                                                                                 
if test "${EDITOR:+is_set}" = 'is_set'; then :; else                                                                                   
    "${CRONTAB_PROG}" "$@"                                                                                                             
    exit $?                                                                                                                            
fi                                                                                                                                     
                                                                                                                                       
: EDITOR: $EDITOR                                                                                                                      
                                                                                                                                       
# We (effectively) only need to wrap crontab(1) when $EDITOR is set to some                                                            
# flavor of emacsclient(1).                                                                                                            
#                                                                                                                                      
case $EDITOR in                                                                                                                        
    */ec-c* | */ec-t* | */emacsclient* )                                                                                               
        # Note that our 'emacsclient' invocations both specify the '-t' opt ("Open a                                                   
        # new Emacs frame on the current terminal"). This is both to avoid the                                                         
        # guesswork that could result in a bogus "*ERROR*: Unknown terminal type"                                                      
        # error (explanation here: https://unix.stackexchange.com/a/119891) and                                                        
        # because we are trying to edit the crontab, damnit, and don't need some                                                       
        # stupid graphical popup editor action.                                                                                        
        #                                                                                                                              
        t_guess_spath_001="/tmp/user/${EUID}/emacs${EUID}/server"                                                                      
        t_guess_spath_002="/tmp/emacs${EUID}/server"                                                                                   
        if test -S "${t_guess_spath_001}"; then                                                                                        
            EDITOR="emacsclient -t -s '${t_guess_spath_001}'" "${CRONTAB_PROG}" "$@"                                                   
        elif test -S "${t_guess_spath_002}"; then                                                                                      
            EDITOR="emacsclient -t -s '${t_guess_spath_002}'" "${CRONTAB_PROG}" "$@"                                                   
        else                                                                                                                           
            EDITOR='vim' "${CRONTAB_PROG}" "$@"                                                                                        
        fi                                                                                                                             
        exit $?                                                                                                                        
        ;;                                                                                                                             
                                                                                                                                       
    *)                                                                                                                                 
        "${CRONTAB_PROG}" "$@"                                                                                                         
        exit $?                                                                                                                        
        ;;                                                                                                                             
esac