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shell基础学习系列（4）：CU Shell版精华练习三则
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本学习笔记都是取自CU Shell版，有很多无法在脚本的版权声明中注明原作者，在此致歉。仅供学习之用，希望后来者亦能有所得。
1、net_state【测试网络状态的脚本】
可以利用ping探测TARGET的存在。这在嵌入式系统中可以取代心跳监测，不仅可以网络保活，而且可以实时测试网络在线状态。
原理就是通过获取返回信息中的损失率来检验网络状态是否良好。缺点就是这并不能作为网络状态是否良好的绝对标准。因为如果对方禁止ICMP回显，则此方法失效。采用心跳监测算是一种比较通用的方法了。
整理脚本如下：
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#!/bin/bash
# Copyright 2007 (c), Shandong University
# All rights reserved.
#
# Filename : net_state
# Description: Test network state, and return 0 if good; else return 1
# Author : Liu Qingmin
# Version : 1.0
# Date : 2007-05-17
#
# Default Variable
NET_GOOD=0 # the value of return if network state is good
E_WRONG_ARGS=1 # error number of return if arguments are wrong
E_NET_NOT_GOOD=2 # error number of return if network state is not good
INTERVAL=3 # the time interval of ping
TIMES=1 # the times every one
LOSSRATE=0 # the loss rate if network is good
# Handle Arguments
case $1 in
"")
echo "Usage: `basename $0` [TARGET]"
exit $E_WRONG_ARGS
;;
*)
TARGET=$1
;;
esac
# Getch the loss rate
lossrate=`ping -i $INTERVAL -c $TIMES $TARGET | \
grep -o "...%" | \
sed 's/,//g' | \
awk -F% '{print $1}'`
# Handle the result
if [ $lossrate != $LOSSRATE ]; then
echo "Network is not good"
exit $E_NET_NOT_GOOD
else
echo "Network is good!"
exit $NET_GOOD
fi
########################## END OF SCRIPT ###########################################
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2、cleanup【日志清理脚本】
这个算是初级版本，毕竟不是做系统管理。只是学习一下而已。
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#!/bin/bash
# Copyright 2007 (c), Shandong University
# All rights reserved.
#
# Filename : cleanup
# Description: clean up /var/log---delete all files before ${SAVE_DAYS}.
# ---restore the $LINES of messages
# Author : Liu Qingmin
# Version : 1.0
# Date : 2007-05-17
#
# Default Variable
TRUE=0 # the value of return if true
FALSE=1 # the value of return if false
NOT_ROOT=2 # the value of return if not root
WRONGARGS=3 # the value of return if args is wrong
E_XCD=4 # cannot excute documents
LOGDIR=/var/log # the log directory
ROOT_UID=0 # the UID of root
# Configuration
LINES=50 # default lines to restore
SAVE_DAYS=7 # default days to save
# test whether the user is the root
is_root()
{
if [ `id -u` != 0 ]; then
return $TRUE
else
return $FALSE
fi
}
###### main func ######
# must be the root
if is_root; then
echo "Must be root to run this script."
exit $NOT_ROOT
fi
# handle parameters
case $1 in
"")
lines=$LINES
;;
*[!0-9]*)
echo "Usage: `basename $0` [lines]"
exit $WRONGARGS
;;
*)
lines=$1
;;
esac
# step into LOGDIR
cd $LOGDIR || {
echo "cannot change to necessary directory."
exit $E_XCD
}
# cleanup
tail -$lines messages > msg.tmp
mv msg.tmp messages
cat /dev/null > wtmp
find $LOGDIR -mtime +$SAVE_DAYS | xargs rm -f
# quit
echo "Logs cleaned up"
exit 0
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3、tr_case.sh【shift用法】
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#!/bin/bash
# Copyright 2007 (c), Shandong University
# All rights reserved.
#
# Filename : tr_case.sh
# Description: convert files to either upper or lower case
# Author : Liu Qingmin
# Version : 1.0
# Date : 2007-05-18
#
# Default Configuration
# Cannot be modified
FILES="" # file list to be dealed with
TRCASE="" # action to be taken
EXT="" # extended name
OPT=no # assure that there is one option at lease
# Default Error Variable
SUCCESS=0 # convert successed or quit normally
FAIL=1 # convert failed
ILLEGAL_OPTION=2 # use illegal option
NO_OPTION=3 # no one option
NO_ARGS=4 # no one argument
# Print Syntax
usage()
{
echo "Usage: `basename $0` -[l | u] file [...]"
}
# Print error information if convertion failed
error_msg()
{
_FILE=$1
echo "`basename $0`: Error! The conversion failed on $_FILE."
}
# Print help information
help()
{
echo
echo "`basename $0` [option] [file]"
echo
echo "Description: "
echo " To convert files to upper or lower case"
echo
echo "option: "
echo " -l convert to lowercase"
echo " -u convert to uppercase"
echo
echo "Usage: "
echo " `basename $0` -[l | u] file [...]"
echo
}
############################## Main Func ###################################
# Make sure that there is one option at least.
if [ $# = 0 ]; then
echo "For more info, please try `basename $0` --help"
exit $NO_ARGS
fi
# Handle options
while [ $# -gt 0 ]; do
case $1 in
# set the variables based on what option was used
-u) # uppercase setup
TRCASE=upper
EXT=".UC"
OPT=yes
shift
;;
-l) # lowercase setup
TRCASE=lower
EXT=".LC"
OPT=yes
shift
;;
--help) # display help information
help
exit $SUCCESS
;;
-*) # deal with illegal option
usage
exit $ILLEGAL_OPTION
;;
*) # deal with file
if [ -f $1 ]; then
FILES=$FILES""$1
else
echo "`basename $0`: cannot find the file $1"
fi
shift
;;
esac
done
# if no options, give help information
if [ "$OPT" = "no" ]; then
echo "`basename $0`: Error! You need to specify an option. No action taken"
echo "try `basename $0` --help"
exit $NO_OPTION
fi
# now read in all the file(s)
for LOOP in $FILES; do
case $TRCASE in
lower) # if lower
cat $LOOP | tr "[A-Z]" "[a-z]" > $LOOP$EXT
if [ $? != 0 ]; then
error_msg $LOOP
exit $FAIL
else
echo "converted file called $LOOP$EXT"
fi
;;
upper) # if upper
cat $LOOP | tr "[a-z]" "[A-Z]" > $LOOP$EXT
if [ $? != 0 ]; then
error_msg $LOOP
exit $FAIL
else
echo "converted file called $LOOP$EXT"
fi
;;
esac
done
# quit successfully
exit $SUCCESS
############################## End of Script ###################################
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测试：
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[armlinux@lqm scripts]$ ./tr_case.sh
For more info, please try tr_case.sh --help
[armlinux@lqm scripts]$ echo $?
4
[armlinux@lqm scripts]$ ./tr_case.sh -k
Usage: tr_case.sh -[l | u] file [...]
[armlinux@lqm scripts]$ echo $?
2
[armlinux@lqm scripts]$ ./tr_case.sh opt.sh
tr_case.sh: You need to specify an option. No action taken
try tr_case.sh --help
[armlinux@lqm scripts]$ echo $?
3
[armlinux@lqm scripts]$ ./tr_case.sh -u opt.sh
converted file called opt.sh.UC
[armlinux@lqm scripts]$ echo $?
0
[armlinux@lqm scripts]$ ./tr_case.sh --help
tr_case.sh [option] [file]
Description:
To convert files to upper or lower case
option:
-l convert to lowercase
-u convert to uppercase
Usage:
tr_case.sh -[l | u] file [...]
[armlinux@lqm scripts]$
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发表于： 2007-05-17，修改于： 2007-11-19 17:01，已浏览1037次，有评论0条
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