sh ？getservbyname的shell脚本版本（3）

Posted 2021-05-07

#!/bin/sh
SERVICES=/etc/services
SED=/bin/sed
GREP=/bin/grep

THIS=$0

usage(){
  echo 'shell-script version of getservbyname(3)'
  echo "usage: ${THIS} <NAME> [<PROTO>]"
  echo 'default PROTO is `tcp`'
  exit 1
}

NAME=$1
[ -z ${NAME} ] && usage

PROTO=$2
[ -z ${PROTO} ] && PROTO='tcp'

delete_comments='s|#.*||g'
delete_empty_lines='/^\s*$/d'
get_port_number="s|^${NAME}\s\s*\\([0-9][0-9]*\\)/${PROTO}.*$|\\1|p"

${SED} -e $delete_comments \
       -e $delete_empty_lines \
       -ne $get_port_number \
       < ${SERVICES}