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Make sed operations in remove only match exact column matches.

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In order to make editing more precise, sed regular expressions only
match exact occurrences of the search string within each entry column.

In order to properly handle tab and space separators in a portable
manner, a set of global variables are included that provide strings
of those characters.
This commit is contained in:
William Melody 2015-06-28 17:26:14 -07:00
parent 46dcff947c
commit 94ca8bfb57
1 changed files with 32 additions and 4 deletions
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34
hosts
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@ -49,6 +49,17 @@ DEFAULT_COMMAND="${DEFAULT_COMMAND:-list}"
# The path to the hosts file. This will almost always be /etc/hosts
HOSTS_PATH="${HOSTS_PATH:-/etc/hosts}"
# Space and tab for regular expressions
#
# sed regular expressions have slightly different behaviors dependending on
# the environment, and POSIX [[:space:]] matches whitespace characters other
# than just space and tab. These variables provide an easier, portable way to
# test for just these two characters.
_TAB_=$'\t'
_SPACE_=$' '
_TAB_SPACE_="${_TAB_}${_SPACE_}"
_TAB_SPACE_CC_="[${_TAB_SPACE_}]"
###############################################################################
# Debug
###############################################################################
@ -872,8 +883,16 @@ remove() {
$_ME help remove
exit 1
else
# Regular Expression Notes
#
# - Note double periods in regular expression in order to emulate /.+/,
# which apparently doesn't work properly with all versions of sed.
local target_records=$(
sed -n "s/^\(.*${search_string}.*\)$/\1/p" "${HOSTS_PATH}"
sed -n \
-e "s/^\(${search_string}[${_TAB_SPACE_}]..*\)$/\1/p" \
-e "s/^\(..*[${_TAB_SPACE_}]${search_string}[${_TAB_SPACE_}]..*\)$/\1/p" \
-e "s/^\(..*[${_TAB_SPACE_}]${search_string}\)$/\1/p" \
"${HOSTS_PATH}"
)
if [[ -z ${target_records:-} ]]
@ -901,9 +920,18 @@ remove() {
esac
done
fi
# -i '' - in place edit. BSD sed requires extension argument, for GNU
# Regular Expression Notes
#
# - -i '' - in place edit. BSD sed requires extension argument, for GNU
# it's optional. More info: http://stackoverflow.com/a/16746032
sed -i '' "/^.*${search_string}.*$/d" "${HOSTS_PATH}"
#
# - Note double periods in regular expression in order to emulate /.+/,
# which apparently doesn't work properly with all versions of sed.
sed -i '' \
-e "/^${search_string}[${_TAB_SPACE_}]..*$/d" \
-e "/^..*[${_TAB_SPACE_}]${search_string}[${_TAB_SPACE_}]..*$/d" \
-e "/^..*[${_TAB_SPACE_}]${search_string}$/d" \
"${HOSTS_PATH}"
printf "Removed:\n%s\n" "${target_records}"
fi
}