Add barebones install and config via env variable

.gitignore

@@ -1 +1,2 @@
 /build
+/src/.slack

Makefile

@@ -10,13 +10,13 @@ install: | stub
 ifeq (${uname}, Darwin)
 	@$(eval _bindir := $(shell greadlink -f ${bindir}))
 	@$(eval _etcdir := $(shell greadlink -f ${etcdir}))
-	@sed -i '' "s|bindir=|bindir=${_bindir}|g" ${bindir}/slack
-	@sed -i '' "s|etcdir=|etcdir=${_etcdir}|g" ${bindir}/slack
+	@sed -i '' "s|bindir=.*|bindir=${_bindir}|g" ${bindir}/slack
+	@sed -i '' "s|etcdir=.*|etcdir=${_etcdir}|g" ${bindir}/slack
 else ifeq (${uname}, Linux)
 	@$(eval _bindir := $(shell readlink -f ${bindir}))
 	@$(eval _etcdir := $(shell readlink -f ${etcdir}))
-	@sed -i "s|bindir=|bindir=${_bindir}|g" ${bindir}/slack
-	@sed -i "s|etcdir=|etcdir=${_etcdir}|g" ${bindir}/slack
+	@sed -i "s|bindir=.*|bindir=${_bindir}|g" ${bindir}/slack
+	@sed -i "s|etcdir=.*|etcdir=${_etcdir}|g" ${bindir}/slack
 endif
 
 stub:

src/slack

@@ -1,8 +1,13 @@
 #!/usr/bin/env bash
 
-bindir=
-etcdir=
-token=$([ -f "${etcdir}/slack" ] && sed -n '1p' < "${etcdir}/slack")
+bindir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+etcdir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+if [ -f "${etcdir}/.slack" ]; then
+  token=$(sed -n '1p' < "${etcdir}/.slack")
+else
+  token="${SLACK_CLI_TOKEN}"
+fi
 
 # COMMAND PARSING #################################################################################
 cmd="${1}" ; shift
@@ -143,7 +148,11 @@ case "${cmd}${sub}" in
     [ -z "${channels}" ] && read -e -p 'Enter channels (e.g. #general,C1234567890): ' channels
   ;;
   init)
-    _token=$([ -f "${etcdir}/slack" ] && sed -n '1p' < "${etcdir}/slack")
+    if [ -f "${etcdir}/.slack" ]; then
+      _token=$(sed -n '1p' < "${etcdir}/.slack")
+    else
+      _token="${SLACK_CLI_TOKEN}"
+    fi
 
     if [ -z "${token}" ] || [ "${token}" == "${_token}" ]; then
       read -e -p 'Enter Slack API token: ' token
@@ -408,7 +417,7 @@ function fileupload() {
 }
 
 function init() {
-  echo "${token}" > "${etcdir}/slack"
+  echo "${token}" > "${etcdir}/.slack"
 
   case "${?}" in
     0) echo '{"ok": true}' | jq -r ${compact} ${monochrome} "${filter:=.}" ;;