cleanup.sh

#!/bin/bash

LOG_DIR=/var/log
ROOT_UID=0
LINES=50
E_XCD=66
E_NOTROOT=67


if [ "$UID" -ne "$ROOT_UID" ]
then
	echo "Must be root to run this script."
	exit $E_NOTROOT
fi

if [ -n "$1" ]
#测试第一个参数非空
then
	lines=$1
else
	lines=$LINES
fi

# 另一种检测命令行的方法
# E_WRONGAGES=65
# 
# case "$1" in
# ""      ) lines=50;;
# *[!0-9]*) echo "Usage: `basename $0` file-to-cleanup"; exit $E_WRONGAGES;;
# *		  ) lines=$1;;
# esac


cd $LOG_DIR

if [ `pwd` != "$LOG_DIR" ]
then
	echo "Can't change to $LOG_DIR"
	exit $E_XCD
fi
#再次确认目录

tail -$lines messages > mesg.temp
mv mesg.temp messages

#cat /dev/null > messages

cat /dev/null > wtmp

echo "Logs cleaned up."

exit 0