From 0664bcb5c8ed61d33ee6bdbc58af3443192cc607 Mon Sep 17 00:00:00 2001
From: Tom Ryder <tom@sanctum.geek.nz>
Date: Mon, 15 Aug 2016 21:38:15 +1200
Subject: Keep grep(1) option metadata in cache

It's stupid to run `grep --help` once per shell (twice for login
shells!) when it's so unlikely to change, and way faster to check for
the presence or absence of hint files rather than pattern-match the
output with the shell.

ls(1) will get the same treatment in a minute.
---
 bash/bashrc.d/grep.bash | 20 +++++++++++---------
 sh/profile.d/grep.sh    | 37 ++++++++++++++++++++++++++-----------
 2 files changed, 37 insertions(+), 20 deletions(-)

diff --git a/bash/bashrc.d/grep.bash b/bash/bashrc.d/grep.bash
index 11eeb5b0..624baf30 100644
--- a/bash/bashrc.d/grep.bash
+++ b/bash/bashrc.d/grep.bash
@@ -1,31 +1,33 @@
+# Our ~/.profile should already have made a directory with the supported
+# options for us
+[[ -d $HOME/.cache/grep ]] || return
+
 # Store whether we have colors in a variable
 declare -i colors
 colors=$( {
     tput Co || tput colors
 } 2>/dev/null )
 
-# Store grep(1)'s --help output in a variable
-grep_help=$(grep --help 2>/dev/null)
-
 # Use GREPOPTS to add some useful options to grep(1) calls if applicable; we
 # use a function wrapper to do this, rather than GREP_OPTIONS as we don't want
 # to change grep(1)'s actual behaviour inside scripts
 declare -a GREPOPTS
-if [[ -n $GREP_COLORS ]] && ((colors >= 8)) ; then
+GREPOPTS=()
+if ((colors >= 8)) && [[ -n $GREP_COLORS ]] ; then
     GREPOPTS[${#GREPOPTS[@]}]='--color=auto'
 fi
-if [[ $grep_help == *--binary-files* ]] ; then
+if [[ -e $HOME/.cache/grep/binary-files ]] ; then
     GREPOPTS[${#GREPOPTS[@]}]='--binary-files=without-match'
 fi
-if [[ $grep_help == *--exclude* ]] ; then
+if [[ -e $HOME/.cache/grep/exclude ]] ; then
     GREPOPTS[${#GREPOPTS[@]}]='--exclude={.gitignore,.gitmodules}'
 fi
-if [[ $grep_help == *--exclude-dir* ]] ; then
+if [[ -e $HOME/.cache/grep/exclude-dir ]] ; then
     GREPOPTS[${#GREPOPTS[@]}]='--exclude-dir={.cvs,.git,.hg,.svn}'
 fi
 
-# Done, unset helper vars
-unset -v grep_help colors
+# Done, unset color var
+unset -v colors
 
 # Define function proper
 grep() {
diff --git a/sh/profile.d/grep.sh b/sh/profile.d/grep.sh
index 87c9a6cc..8c1c5836 100644
--- a/sh/profile.d/grep.sh
+++ b/sh/profile.d/grep.sh
@@ -1,13 +1,28 @@
-# Store grep(1)'s --help output in a variable
-grep_help=$(grep --help 2>/dev/null)
+# Test that we have metadata about what options this system's grep(1) supports,
+# and try to create it if not
+(
+    # Create a directory to hold metadata about grep
+    gcd=$HOME/.cache/grep
+    if ! [ -d "$gcd" ] ; then
+        mkdir -p -- "$gcd" || exit
+    fi
 
-# Set and export GREP_COLORS if available and appropriate
-case $grep_help in
-    *--color*)
-        GREP_COLORS='ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36'
-        export GREP_COLORS
-        ;;
-esac
+    # Write grep(1)'s --help output to a file, even if it's empty
+    if ! [ -f "$gcd"/help ] ; then
+        grep --help </dev/null >"$gcd"/help 2>/dev/null || exit
 
-# We're done parsing grep(1)'s --help output now
-unset -v grep_help
+        # Iterate through some useful options and create files to show they're
+        # available
+        for opt in binary-files color exclude exclude-dir ; do
+            grep -q -- --"$opt" "$gcd"/help || continue
+            touch -- "$gcd"/"$opt" || exit
+        done
+    fi
+) || return
+
+# If one of the available options is --color, set the GREP_COLORS environment
+# variable
+if [ -e "$HOME"/.cache/grep/color ] ; then
+    GREP_COLORS='ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36'
+    export GREP_COLORS
+fi
-- 
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