commit: f85980a40cc0d39138e0e363f5430c7e339e2bf5
parent: 61be5af0990a3eac7ecdaa9a1ce78e4039ac85ac
author: z0noxz <chris@noxz.tech>
date: Mon, 6 Aug 2018 21:45:36 +0200
make POSIX compliant
1 file changed, 34 insertions(+), 31 deletions(-)
diff --git a/cidr2ip b/cidr2ip
@@ -1,5 +1,5 @@
#!/bin/sh
-read -d '' license << EOF
+license='
Converts CIDR to IPADDRESS
Copyright (C) 2018 z0noxz, <chris@noxz.tech>
@@ -15,45 +15,48 @@ GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
-EOF
-
-function cidr2ip {
-
- local binary=""
- local oct1=""
- local oct2=""
- local oct3=""
- local oct4=""
-
- binary=$(printf '1%.0s' $(eval "printf '%1.0s\.' {1..$(($1))}"))
- binary=${binary}$(printf '0%.0s' $(eval "printf '%1.0s\.' {0..$((32-$1))}"))
- oct1="${binary:0:8}"
- oct2="${binary:8:8}"
- oct3="${binary:16:8}"
- oct4="${binary:24:8}"
-
- printf "%d.%d.%d.%d\n"\
- "$((2#${oct1}))"\
- "$((2#${oct2}))"\
- "$((2#${oct3}))"\
- "$((2#${oct4}))"
+'
+
+cidr2ip() {
+
+ cidr=$1
+ cidr_invert=$((32-cidr))
+ mask=$((4294967295 >> cidr_invert << cidr_invert))
+ base=256
+ result=""
+
+ while [ "$mask" -ne 0 ]; do
+ result=$(printf '%3s%s' $((mask % base)) "$result")
+ mask=$((mask / base))
+ done
+
+ oct1=${result%?????????}
+ oct2=${result%??????}
+ oct3=${result%???}
+ oct4=${result#?????????}
+
+ oct2=${oct2#???}
+ oct3=${oct3#??????}
+
+ printf '%d.%d.%d.%d\n'\
+ "$oct1"\
+ "$oct2"\
+ "$oct3"\
+ "$oct4"
}
# check if input is a CIDR
-if [[ $1 =~ ^[0-9]{1,2}$ && $1 -le 32 && $1 -gt 0 ]]; then
- cidr2ip $1
+if [ "$1" -eq "$1" ] 2> /dev/null && [ "$1" -le 32 ] && [ "$1" -gt 0 ]; then
+ cidr2ip "$1"
exit 0
fi
# if all fails print usage
program_name="${0##*/}"
-read -d '' usage << EOF
-Usage: $program_name CIDR
+printf 'Usage: %s CIDR
LICENSE NOTICE
-
-$license
-EOF
-printf "%s\n\n" "$usage" >&2
+%s
+' "$program_name" "$license" >&2
exit 1
