Fast algorithm to determine grep alias flags

This version tries whether grep supports all the flags together
and progressively checks older flags if the grep test fails.
This means only one grep call if all flags are supported, and
one additional call for every flag that's not supported, up to
a maximum of 3 calls.
This commit is contained in:
Marc Cornellà 2020-03-01 14:02:06 +01:00
parent 57b178102c
commit 8d814fdff6

View file

@ -4,37 +4,36 @@ if (( $#_grep_alias_cache )); then
source "$ZSH_CACHE_DIR"/grep_alias.zsh
else
# is x grep argument available?
grep-flag-available() {
echo | grep $1 "" >/dev/null 2>&1
grep-flags-available() {
echo | grep "$@" "" >/dev/null 2>&1
}
GREP_OPTIONS=""
# color grep results
if grep-flag-available --color=auto; then
GREP_OPTIONS+=" --color=auto"
fi
# ignore these folders (if the necessary grep flags are available)
EXC_FOLDERS="{.bzr,CVS,.git,.hg,.svn,.idea,.tox}"
if grep-flag-available --exclude-dir=.cvs; then
GREP_OPTIONS+=" --exclude-dir=$EXC_FOLDERS"
elif grep-flag-available --exclude=.cvs; then
GREP_OPTIONS+=" --exclude=$EXC_FOLDERS"
if grep-flags-available --color=auto --exclude-dir=.cvs; then
GREP_OPTIONS+="--color=auto --exclude-dir=$EXC_FOLDERS"
elif grep-flags-available --color=auto --exclude=.cvs; then
GREP_OPTIONS+="--color=auto --exclude=$EXC_FOLDERS"
elif grep-flags-available --color=auto; then
GREP_OPTIONS+="--color=auto"
fi
{
if [[ -n "$GREP_OPTIONS" ]]; then
# export grep, egrep and fgrep settings
echo alias grep="'grep $GREP_OPTIONS'"
echo alias egrep="'egrep $GREP_OPTIONS'"
echo alias fgrep="'fgrep $GREP_OPTIONS'"
fi
} > "$ZSH_CACHE_DIR/grep_alias.zsh"
source "$ZSH_CACHE_DIR/grep_alias.zsh"
# clean up
unset GREP_OPTIONS EXC_FOLDERS
unfunction grep-flag-available
unfunction grep-flags-available
fi
unset _grep_alias_cache