7. Shell 脚本编写

1、提示用户输入一个字符串，如果是 hello，打出 yes，并每秒输出 "hello，world"，否则就输出 no，实现如下：

#!/bin/bash

#Filename:hello.sh

echo "Please input 'hello'"

read -p "> " str // 得到键盘输入

echo $str

if [ "$str" == hello ]

then

echo "yes"

while true

echo "hello, world"

sleep 1 // 睡眠1秒

done

else

echo "no"

2、实现一个 find.sh，运行 ./find.sh /tmp/test.txt ，当 /tmp/test.txt 为文件且存在时输出 yes, 否则输出 no，实现如下：

#!/bin/bash

#Filename:find.sh

args1=$1 ( $0 为要执行的文件路径，$1 为输入的第一个参数，以此类推)

if [ -e "$args1" ] // 如果该变量代表的值是一个文件

then

echo "yes"

else

echo "no"

判断文件的参数如下：

-e 文件存在
-f file 是一个 regular 文件(不是目录或者设备文件)
-s 文件长度不为 0
-d 文件是个目录
-b 文件是个块设备(软盘,cdrom 等等)
-c 文件是个字符设备(键盘,modem,声卡等等)
-p 文件是个管道
-h 文件是个符号链接
-L 文件是个符号链接
-S 文件是个 socket
-t 关联到一个终端设备的文件描述符这个选项一般都用来检测是否在一个给定脚本中的 stdin[-t0]或[-t1]是一个终端
-r 文件具有读权限(对于用户运行这个 test)
-w 文件具有写权限(对于用户运行这个 test)
-x 文件具有执行权限(对于用户运行这个 test)

3、实现一个 ping.sh

运行 ./ping.sh start 后在后台运行 ping 命令，ping 127.0.0.1，并把 ping 结果输出到 /tmp/ping.log
运行 ./ping.sh status 显示 ping 命令是否正在运行
运行 ./ping.sh stop 停止 ping 命令，如果正在运行的话。

# 方法一：输入 stop 时，直接关闭所有的 ping 进程

#!/bin/bash

#Filaname:ping.sh

if [ "$1" == "start" ]

then

ping 127.0.0.1 > /tmp/ping.log &

elif [ "$1" == "status" ]

then

ps -ef | grep "ping 127.0.0.1"

elif [ "$1" == "stop" ]

then

killall ping (会干掉所有的ping 进程，包括子进程)

#方法二：得到ping 127.0.0.1 的进程 ID ，再用kill 结束掉

#!/bin/bash

#Filaname:ping.sh

if [ "$1" == "start" ]

then

ping 127.0.0.1 > /tmp/ping.log &

elif [ "$1" == "status" ]

then

ps -ef | grep "ping 127.0.0.1"

elif [ "$1" == "stop" ]

then

pid=`ps -ef |grep ping | grep "127.0.0.1" | awk '{print $2}'`

if [ "pid" -gt 0 ];then

kill $pid

echo kill $pid

else

echo "要关闭的进程不存在"

3、将上面的 ping.sh 加入开机自启动

系统的rc.local 文件是在系统启动之后才加载的，可以把脚本添加到这个文件中

打开 /etc/rc.d/rc.local 文件（root 用户）：vim /etc/rc.d/rc.local

加入下面两行：

cd /home/demon # 进入到当前目录

su demon -c "./ping.sh start"

4、解析 mysql.server 脚本的作用

mysql.server 是用来打开或关闭 mysql 服务

#!/bin/sh

basedir=

datadir=

service_startup_timeout=900 #服务启动超时时间

lockdir='/var/lock/subsys'

lock_file_path="$lockdir/mysql"

mysqld_pid_file_path=

# 判断 $basedir 的长度是否为 0

if test -z "$basedir"

then

basedir=/usr/local/mysql

bindir=/usr/local/mysql/bin

if test -z "$datadir"

then

datadir=/usr/local/mysql/data

sbindir=/usr/local/mysql/bin

libexecdir=/usr/local/mysql/bin

else

bindir="$basedir/bin"

if test -z "$datadir"

then

datadir="$basedir/data"

sbindir="$basedir/sbin"

libexecdir="$basedir/libexec"

datadir_set=

lsb_functions="/lib/lsb/init-functions"

# 判断是否是一个文件，并存在

if test -f $lsb_functions ; then

. $lsb_functions

else

log_success_msg()

{

echo " SUCCESS! $@"

}

log_failure_msg()

{

echo " ERROR! $@"

}

#添加 PATH 到环境变量中

PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin"

export PATH

# mode 是传入的第一个参数，用于判断启动脚本是开启 mysql 服务，还是关闭

mode=$1 # start or stop

# 判断参数的数量是否大于 1

# $# 为参数的数量，-ge 大于(数字比较)，当 && 左边的表达式为真时，才会执行右边的表达式，

# shift 表示左移，shift 2表示左移两个，&4 移到 &2，&3 移到 &1，原来的&1,、&2被丢弃吊了，而 &0 不会被影响；不带参数的相当于 shift 1

[ $# -ge 1 ] && shift

other_args="$*" # uncommon, but needed when called from an RPM upgrade action

# Expected: "--skip-networking --skip-grant-tables"

# They are not checked here, intentionally, as it is the resposibility

# of the "spec" file author to give correct arguments only.

case `echo "testing\c"`,`echo -n testing` in

*c*,-n*) echo_n= echo_c= ;;

*c*,*) echo_n=-n echo_c= ;;

*) echo_n= echo_c='\c' ;;

esac

parse_server_arguments() {

for arg do

case "$arg" in

--basedir=*) basedir=`echo "$arg" | sed -e 's/^[^=]*=//'`

bindir="$basedir/bin"

if test -z "$datadir_set"; then

datadir="$basedir/data"

sbindir="$basedir/sbin"

libexecdir="$basedir/libexec"

;;

--datadir=*) datadir=`echo "$arg" | sed -e 's/^[^=]*=//'`

datadir_set=1

;;

--pid-file=*) mysqld_pid_file_path=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;

--service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;

esac

done

}

wait_for_pid () {

verb="$1" # created | removed

pid="$2" # process ID of the program operating on the pid-file

pid_file_path="$3" # path to the PID file.

i=0

avoid_race_condition="by checking again"

while test $i -ne $service_startup_timeout ; do

case "$verb" in

'created')

# wait for a PID-file to pop into existence.

test -s "$pid_file_path" && i='' && break

;;

'removed')

# wait for this PID-file to disappear

test ! -s "$pid_file_path" && i='' && break

;;

echo "wait_for_pid () usage: wait_for_pid created|removed pid pid_file_path"

exit 1

;;

esac

# if server isn't running, then pid-file will never be updated

if test -n "$pid"; then

if kill -0 "$pid" 2>/dev/null; then

: # the server still runs

else

# The server may have exited between the last pid-file check and now.

if test -n "$avoid_race_condition"; then

avoid_race_condition=""

continue # Check again.

# there's nothing that will affect the file.

log_failure_msg "The server quit without updating PID file ($pid_file_path)."

return 1 # not waiting any more.

echo $echo_n ".$echo_c"

i=`expr $i + 1`

sleep 1

done

if test -z "$i" ; then

log_success_msg

return 0

else

log_failure_msg

return 1

}

# Get arguments from the my.cnf file,

# the only group, which is read from now on is [mysqld]

# test -x 判断文件是否可执行

if test -x ./bin/my_print_defaults

then

print_defaults="./bin/my_print_defaults"

elif test -x $bindir/my_print_defaults

then

print_defaults="$bindir/my_print_defaults"

elif test -x $bindir/mysql_print_defaults

then

print_defaults="$bindir/mysql_print_defaults"

else

# Try to find basedir in /etc/my.cnf

conf=/etc/my.cnf

print_defaults=

# 判断文件是否可读

if test -r $conf

then

subpat='^[^=]*basedir[^=]*=$.*$$'

dirs=`sed -e "/$subpat/!d" -e 's//\1/' $conf`

for d in $dirs

d=`echo $d | sed -e 's/[ ]//g'`

if test -x "$d/bin/my_print_defaults"

then

print_defaults="$d/bin/my_print_defaults"

break

if test -x "$d/bin/mysql_print_defaults"

then

print_defaults="$d/bin/mysql_print_defaults"

break

done

# Hope it's in the PATH ... but I doubt it

# 判断字符串长度是否为 0

test -z "$print_defaults" && print_defaults="my_print_defaults"

# Read defaults file from 'basedir'. If there is no defaults file there

# check if it's in the old (depricated) place (datadir) and read it from there

extra_args=""

if test -r "$basedir/my.cnf"

then

extra_args="-e $basedir/my.cnf"

else

if test -r "$datadir/my.cnf"

then

extra_args="-e $datadir/my.cnf"

parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`

# Set pid file if not given

if test -z "$mysqld_pid_file_path"

then

mysqld_pid_file_path=$datadir/`hostname`.pid

else

case "$mysqld_pid_file_path" in

/* ) ;;

* ) mysqld_pid_file_path="$datadir/$mysqld_pid_file_path" ;;

esac

case "$mode" in

'start')

# Start daemon

# Safeguard (relative paths, core dumps..)

cd $basedir

echo $echo_n "Starting MySQL"

if test -x $bindir/mysqld_safe

then

# Give extra arguments to mysqld with the my.cnf file. This script

# may be overwritten at next upgrade.

$bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &

wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$?

# Make lock for RedHat / SuSE

if test -w "$lockdir"

then

touch "$lock_file_path"

exit $return_value

else

log_failure_msg "Couldn't find MySQL server ($bindir/mysqld_safe)"

;;

'stop')

# Stop daemon. We use a signal here to avoid having to know the

# root password.

if test -s "$mysqld_pid_file_path"

then

mysqld_pid=`cat "$mysqld_pid_file_path"`

if (kill -0 $mysqld_pid 2>/dev/null)

then

echo $echo_n "Shutting down MySQL"

kill $mysqld_pid

# mysqld should remove the pid file when it exits, so wait for it.

wait_for_pid removed "$mysqld_pid" "$mysqld_pid_file_path"; return_value=$?

else

log_failure_msg "MySQL server process #$mysqld_pid is not running!"

rm "$mysqld_pid_file_path"

# Delete lock for RedHat / SuSE

if test -f "$lock_file_path"

then

rm -f "$lock_file_path"

exit $return_value

else

log_failure_msg "MySQL server PID file could not be found!"

;;

'restart')

# Stop the service and regardless of whether it was

# running or not, start it again.

if $0 stop $other_args; then

$0 start $other_args

else

log_failure_msg "Failed to stop running server, so refusing to try to start."

exit 1

;;

'reload'|'force-reload')

if test -s "$mysqld_pid_file_path" ; then

read mysqld_pid < "$mysqld_pid_file_path"

kill -HUP $mysqld_pid && log_success_msg "Reloading service MySQL"

touch "$mysqld_pid_file_path"

else

log_failure_msg "MySQL PID file could not be found!"

exit 1

;;

'status')

# First, check to see if pid file exists

if test -s "$mysqld_pid_file_path" ; then

read mysqld_pid < "$mysqld_pid_file_path"

if kill -0 $mysqld_pid 2>/dev/null ; then

log_success_msg "MySQL running ($mysqld_pid)"

exit 0

else

log_failure_msg "MySQL is not running, but PID file exists"

exit 1

else

# Try to find appropriate mysqld process

mysqld_pid=`pidof $libexecdir/mysqld`

# test if multiple pids exist

pid_count=`echo $mysqld_pid | wc -w`

if test $pid_count -gt 1 ; then

log_failure_msg "Multiple MySQL running but PID file could not be found ($mysqld_pid)"

exit 5

elif test -z $mysqld_pid ; then

if test -f "$lock_file_path" ; then

log_failure_msg "MySQL is not running, but lock file ($lock_file_path) exists"

exit 2

log_failure_msg "MySQL is not running"

exit 3

else

log_failure_msg "MySQL is running but PID file could not be found"

exit 4

;;

# usage

basename=`basename "$0"`

echo "Usage: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]"

exit 1

;;

esac

exit 0

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