Linux学习笔记--Shell基本操作
基本输出全局变量
[stephen@CentOS04 ~]$ su - # 切换为root用户 Password: [root@CentOS04 ~]# mkdir scripts [root@CentOS04 ~]# cd scripts/ [root@CentOS04 scripts]# ls [root@CentOS04 scripts]# echo $HOME # 显示当前用户主目录 /root [root@CentOS04 scripts]# echo $USER # 显示当前用户账号 root [root@CentOS04 ~]# echo $UID # 显示root用户UID 0 [root@CentOS04 test]# echo $SHELL # 显示当前使用的SHELL版本 /bin/bash [root@CentOS04 test]# grep root /etc/passwd # 查看OS使用的是哪种SHELL root:x:0:0:root:/root:/bin/bash operator:x:11:0:operator:/root:/sbin/nologin [root@CentOS04 scripts]# logout # 切换回用户stephen [stephen@CentOS04 ~]$ echo $HOME /home/stephen [stephen@CentOS04 ~]$ echo $USER stephen [stephen@CentOS04 ~]$ echo $UID 501 [stephen@CentOS04 ~]$ echo $SHELL /bin/bash [stephen@CentOS04 ~]$ echo $PS1 # 当前用户命令前缀格式：user/host/当前路径 [\u@\h \W]\$ [stephen@CentOS04 ~]$ echo $HOSTTYPE # 当前服务器CPU架构 x86_64
写文件
[root@CentOS04 sysconfig]# cd /root/test/ [root@CentOS04 test]# ls [root@CentOS04 test]# echo stephen > test.log # echo写内容 [root@CentOS04 test]# cat test.log stephen [root@CentOS04 test]# >test.log # 写入空内容 [root@CentOS04 test]# cat test.log # 无结果显示 [root@CentOS04 test]# echo >test.log # echo写入空内容 [root@CentOS04 test]# cat test.log # 结果显示空内容 [root@CentOS04 test]# cat /dev/null >test.log # 另外一种方式写入空内容 [root@CentOS04 test]# cat test.log
定义环境变量
[root@CentOS04 test]# tac /etc/init.d/nfs # 与cat相反，倒序输出 ... # the NFS services. # nfs This shell script takes care of starting and stopping # #!/bin/sh # 可直接在最尾看到文件第一行内容 [root@CentOS04 test]# head -1 /etc/init.d/nfs # 使用head -1查看文件第一行内容 #!/bin/sh
“#”的使用
[root@CentOS04 test]# vi test.sh "test.sh" [New] 5L, 92C written [root@CentOS04 test]# cat test.sh #!/bin/bash # 声明环境变量 echo "stephen start" #!/bin/bash <== comment here! # 此处注释 #!/bin/sh # 此处注释 echo "stephen end" [root@CentOS04 test]# sh test.sh stephen start stephen end
查看官方SHELL书写规范
[stephen@CentOS04 ~]$ cat /etc/bashrc # bashrc文件提供标准SHELL书写规范 # /etc/bashrc # System wide functions and aliases # Environment stuff goes in /etc/profile # It's NOT a good idea to change this file unless you know what you # are doing. It's much better to create a custom.sh shell script in # /etc/profile.d/ to make custom changes to your environment, as this # will prevent the need for merging in future updates. ... [stephen@CentOS04 ~]$ cat /etc/profile # profile文件提供许多方法供阅读 # /etc/profile # System wide environment and startup programs, for login setup # Functions and aliases go in /etc/bashrc # It's NOT a good idea to change this file unless you know what you # are doing. It's much better to create a custom.sh shell script in # /etc/profile.d/ to make custom changes to your environment, as this # will prevent the need for merging in future updates. ... [stephen@CentOS04 ~]$ cd /etc/profile.d/ # vim的SHELL文件位置 [stephen@CentOS04 profile.d]$ ll total 52 -rw-r--r--. 1 root root 1127 Mar 5 20:17 colorls.csh -rw-r--r--. 1 root root 1143 Mar 5 20:17 colorls.sh -rw-r--r--. 1 root root 92 Nov 22 2013 cvs.csh -rw-r--r--. 1 root root 78 Nov 22 2013 cvs.sh -rw-r--r--. 1 root root 192 Feb 24 22:24 glib2.csh -rw-r--r--. 1 root root 192 Feb 24 22:24 glib2.sh -rw-r--r--. 1 root root 1741 Feb 20 18:44 lang.csh -rw-r--r--. 1 root root 2706 Feb 20 18:44 lang.sh -rw-r--r--. 1 root root 122 Feb 7 2007 less.csh -rw-r--r--. 1 root root 108 Feb 7 2007 less.sh -rw-r--r--. 1 root root 97 Apr 5 2012 vim.csh -rw-r--r--. 1 root root 269 Apr 5 2012 vim.sh -rw-r--r--. 1 root root 169 May 20 2009 which2.sh
编辑profile文件
[stephen@CentOS04 ~]$ echo $TMOUT [stephen@CentOS04 ~]$ echo $HISTFILESIZE 1000 [stephen@CentOS04 ~]$ vi /etc/profile # /etc/profile ... HISTFILESIZE=5 HISTSIZE=5 # 历史记录大小？行数？ TMOUT=5 # 5s后自动logout "/etc/profile" 81L, 1830C written [stephen@CentOS04 ~]$ . /etc/profile # 修改配置后需载入才能生效 [stephen@CentOS04 ~]$ timed out waiting for input: auto-logout # 自动登出 ... [stephen@CentOS04 ~]$ echo $TMOUT # 后改为600 600 [stephen@CentOS04 ~]$ history # 显示历史记录（5行） 8 vi /etc/profile 9 sudo vi /etc/profile 10 . /etc/profile 11 echo $TMOUT 12 history
手工加入全局变量
[stephen@CentOS04 ~]$ sudo vi /etc/profile # /etc/profile ... TMOUT=600 export stephen="I am stephen" # 定义全局变量stephen "/etc/profile" 83L, 1863C written [stephen@CentOS04 ~]$ tail -1 /etc/profile export stephen="I am stephen" [stephen@CentOS04 ~]$ echo $stephen # 未加载，没有显示 [stephen@CentOS04 ~]$ su - Password: [root@CentOS04 ~]# cd scripts/ [root@CentOS04 scripts]# . /etc/profile # 加载profile文件 [root@CentOS04 scripts]# echo $stephen # 显示全局变量 I am stephen [root@CentOS04 scripts]# ls [root@CentOS04 scripts]# vi m2.sh "m2.sh" [New] 1L, 9C written [root@CentOS04 scripts]# cat m2.sh # 自定义SHELL文件用于显示全局变量 echo $stephen [root@CentOS04 scripts]# sh m2.sh I am stephen
查询系统环境变量：printenv
[root@CentOS04 scripts]# printenv HOSTNAME=CentOS04.stephenzhou.net SHELL=/bin/bash TERM=xterm HISTSIZE=1000 OLDPWD=/root stephen=I am stephen USER=root LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arj=01;31:*.taz=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lz=01;31:*.xz=01;31:*.bz2=01;31:*.tbz=01;31:*.tbz2=01;31:*.bz=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.rar=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36: MAIL=/var/spool/mail/root PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin PWD=/root/scripts LANG=en_US.UTF-8 HISTCONTROL=ignoredups SHLVL=1 HOME=/root LOGNAME=root CVS_RSH=ssh LESSOPEN=|/usr/bin/lesspipe.sh %s G_BROKEN_FILENAMES=1 _=/usr/bin/printenv
无引号、单引号及双引号的用法
[root@CentOS04 scripts]# a=192.168.1.2
[root@CentOS04 scripts]# b='192.168.1.3'
[root@CentOS04 scripts]# c="192.168.1.4"
[root@CentOS04 scripts]# echo "a=$a"
a=192.168.1.2
[root@CentOS04 scripts]# echo "b=$b"
b=192.168.1.3
[root@CentOS04 scripts]# echo "c=$c"
c=192.168.1.4
[root@CentOS04 scripts]# echo "c=${c}"
c=192.168.1.4
[root@CentOS04 scripts]# a=192.168.1.2-$a # 无引号可引入变量
[root@CentOS04 scripts]# b='192.168.1.2-$a' # 单引号全引用
[root@CentOS04 scripts]# c="192.168.1.2-$a" # 双引号可引入变量
[root@CentOS04 scripts]# echo "a=$a"
a=192.168.1.2-192.168.1.2
[root@CentOS04 scripts]# echo "b=$b"
b=192.168.1.2-$a
[root@CentOS04 scripts]# echo "c=${c}"
c=192.168.1.2-192.168.1.2-192.168.1.2
[root@CentOS04 scripts]# echo '`date`'
`date`
[root@CentOS04 scripts]# echo "`date`"
Wed Jun 25 19:27:59 CST 2014
[root@CentOS04 scripts]# echo `date`
Wed Jun 25 19:28:32 CST 2014
[root@CentOS04 scripts]# ETT=123
[root@CentOS04 scripts]# awk 'BEGIN {print '$ETT'}' # awk中用法相反
123
[root@CentOS04 scripts]# awk 'BEGIN {print "$ETT"}'
$ETT
通过读取HOSTS文件，输入IP显示主机名
方法一：通过grep过滤
[root@CentOS04 scripts]# vi /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.2.2 dc01 dc01.stephenzhou.net
192.168.2.31 ex2013a ex2013a.stephenzhou.net
"/etc/hosts" 4L, 241C written
[root@CentOS04 scripts]# vi judgehost.sh
#!/bin/bash
echo "please input ip address:"
read ip
[ -n "`grep "$ip " /etc/hosts`" ] && \
echo "The hostname is: `grep "$ip " /etc/hosts |awk '{print $2}'`" || \
echo "The ip is invalid"
"judgehost.sh" 6L, 188C written
[root@CentOS04 scripts]# bash judgehost.sh
please input ip address:
192.168.2.2
The hostname is: dc01
[root@CentOS04 scripts]# bash judgehost.sh
please input ip address:
192.168.2.31
The hostname is: ex2013a
[root@CentOS04 scripts]# bash judgehost.sh
please input ip address:
localhost
The hostname is: localhost
localhost
[root@CentOS04 scripts]# mv judgehost.sh judgehost_grep.sh
[root@CentOS04 scripts]# ls
judgehost_grep.sh m2.sh
方法二：通过awk过滤
[root@CentOS04 scripts]# mv judgehost.sh judgehost_grep.sh
[root@CentOS04 scripts]# ls
judgehost_grep.sh m2.sh
[root@CentOS04 scripts]# vi judgehost_flag.sh
#!/bin/bash
#judge input
if [ $# -ne 1 ]
then
echo "input error!"
exit 1
fi
flag=0
exec < /etc/hosts
while read line
do
if { "$1" = "`echo $line|awk '{print $1}'`" }
then
flag=1
echo "the $1 's hostname is `echo $line|awk '{print $2}'`"
break;
fi
done
[ $flag -eq 0 ] && echo "sorry, not fine $1 's hostname!"
"judgehost_flag.sh" 20L, 329C written
[root@CentOS04 scripts]# vi awkhost1.sh
awk 'BEGIN {a="'$1'"} {if($1==a) print $2; }' /etc/hosts
"awkhost1.sh" [New] 1L, 57C written
[root@CentOS04 scripts]# sh awkhost1.sh 192.168.2.2
dc01
[root@CentOS04 scripts]# vi awkhost2.sh
awk '{if($1=="'$1'") print $2}' /etc/hosts
"awkhost2.sh" [New] 1L, 43C written
[root@CentOS04 scripts]# sh awkhost2.sh 192.168.2.2
dc01
操作系统定义函数/etc/init.d/functions
[stephen@CentOS04 ~]$ more /etc/init.d/functions # 大量系统自带函数（checkpid()/killproc()/echo_success()/）定义 # -*-Shell-script-*- # # functions This file contains functions to be used by most or all # shell scripts in the /etc/init.d directory. # ...
定义系统变量
[root@CentOS04 ~]# ls
abccs.dbb anaconda-ks.cfg iis install.log install.log.syslog mytable.txt scripts test title.txt
[root@CentOS04 ~]# echo $cmd
[root@CentOS04 ~]# cmd=`ls` # 定义cmd为系统变量ls
[root@CentOS04 ~]# echo $cmd
abccs.dbb anaconda-ks.cfg iis install.log install.log.syslog mytable.txt scripts test title.txt
[root@CentOS04 ~]# cmd=`date +%F` # 定义cmd为当前时间
[root@CentOS04 ~]# echo $cmd
2014-06-25
[root@CentOS04 ~]# cmd=$(date +%F) # 可用``，亦可用()
[root@CentOS04 ~]# echo $cmd
2014-06-25
[root@CentOS04 ~]# tar zcf etc_${cmd}_stephen.tar.gz /etc # 利用系统变量（时间）对文件名进行修改
tar: Removing leading `/' from member names
tar: Removing leading `/' from hard link targets
[root@CentOS04 ~]# ll etc_*
-rw-r--r--. 1 root root 8715620 Jun 25 20:37 etc_2014-06-25_stephen.tar.gz
[root@CentOS04 ~]# uname -n
CentOS04.stephenzhou.net
[root@CentOS04 ~]# tar zcf etc_`uname -n`.tar.gz /etc/ # 利用系统变量（主机名）对文件名进行修改
tar: Removing leading `/' from member names
tar: Removing leading `/' from hard link targets
[root@CentOS04 ~]# ll etc_*
-rw-r--r--. 1 root root 8715620 Jun 25 20:37 etc_2014-06-25_stephen.tar.gz
-rw-r--r--. 1 root root 8715620 Jun 25 20:47 etc_CentOS04.stephenzhou.net.tar.gz
[root@CentOS04 ~]# hostname=$(uname -n) # 系统变量（主机名）赋予主机名
[root@CentOS04 ~]# echo $hostname
CentOS04.stephenzhou.net
位置变量
$0
[root@CentOS04 scripts]# cat 0.sh echo $0 [root@CentOS04 scripts]# sh 0.sh # $0用于获取当前执行的SHELL脚本的文件名 0.sh [root@CentOS04 scripts]# sh /root/scripts/0.sh /root/scripts/0.sh [root@CentOS04 scripts]# cat 0.sh dirname $0 # 路径名 basename $0 # 文件名 [root@CentOS04 scripts]# sh /root/scripts/0.sh /root/scripts 0.sh [root@CentOS04 scripts]# sh 0.sh $0 . 0.sh [root@CentOS04 scripts]# sh /root/scripts/0.sh /root/scripts 0.sh
-
$1/$2/$3...
[root@CentOS04 scripts]# seq -s " $" 0 10
0 $1 $2 $3 $4 $5 $6 $7 $8 $9 $10
[root@CentOS04 scripts]# seq 9|sed 's#[0-9]#$&#g'
$1
$2
$3
$4
$5
$6
$7
$8
$9
[root@CentOS04 scripts]# cat n.sh
echo $1 $2 $3 $4 $5 $6 $7 $8 $9 $10
[root@CentOS04 scripts]# sh n.sh kk ff # $1对应第一位kk，$2对应第二位ff
kk ff kk0 # kk0则为{$1}0->kk0
[root@CentOS04 scripts]# vi n.sh
echo $1 $2 $3 $4 $5 $6 $7 $8 $9 $10
"n.sh" 1L, 38C written
[root@CentOS04 scripts]# sh n.sh kk ff
kk ff
[root@CentOS04 scripts]# sh n.sh `seq -s " " 10` # 自动生成数字1~10
1 2 3 4 5 6 7 8 9 10
-
$#
[root@CentOS04 scripts]# vi n.sh
echo $1 $2 $3 $4 $5 $6 $7 $8 $9 ${10}
echo $#
"n.sh" 2L, 46C written
[root@CentOS04 scripts]# sh n.sh `seq -s " " 10`
1 2 3 4 5 6 7 8 9 10
10 # $#为显示参数总个数
-
$?
[root@CentOS04 scripts]# stephen -bash: stephen: command not found [root@CentOS04 scripts]# echo $? # 获取上个指令的返回值 127 [root@CentOS04 scripts]# pwd /root/scripts [root@CentOS04 scripts]# echo $? 0
-
位置变量总结
[root@CentOS04 scripts]# vi all.sh "all.sh" [New] 10L, 325C written [root@CentOS04 scripts]# cat all.sh echo '$0 Get file name:' $0 echo '$n Get nth args, n=1...9:' '$1'=$1 '$2'=$2 "\$3=$3" echo '$* Get all args...' $* echo '$# return count:' $# echo '$$ Return PID:' $$ sleep 2 & echo '$! exec last command's PID:' $! echo '$? return last command's return value:' $? echo '$@ all args:' $@ echo '$_ last command's last arg:' $_ [root@CentOS04 scripts]# sh all.sh stephen stan zac $0 Get file name: all.sh $n Get nth args, n=1...9: $1=stephen $2=stan $3=zac $* Get all args... stephen stan zac $# return count: 3 $$ Return PID: 5624 $! exec last commands PID: $! echo 0 return last commands return value: 0 $@ all args: stephen stan zac all.sh: line 10: unexpected EOF while looking for matching `'' all.sh: line 11: syntax error: unexpected end of file
-
$*及$@
[root@CentOS04 scripts]# set -- "I am" handsome stephen. [root@CentOS04 scripts]# for i in $*;do echo $i;done I am handsome stephen. [root@CentOS04 scripts]# for i in $@;do echo $i;done I am handsome stephen. [root@CentOS04 scripts]# for i;do echo $i;done # 不加范围等同"$@" I am handsome stephen. [root@CentOS04 scripts]# for i in "$@";do echo $i;done # "$@"这个程序的所有参数 I am handsome stephen. [root@CentOS04 scripts]# for i in "$*";do echo $i;done # "$*"获取当前所有参数 I am handsome stephen.
-
位置及分片
[root@CentOS04 ~]# OLDBOY="I am stephen"
[root@CentOS04 ~]# echo $OLDBOY
I am stephen
[root@CentOS04 ~]# echo ${#OLDBOY} # 获得字节个数
12
[root@CentOS04 ~]# echo $OLDBOY|wc -m
13
[root@CentOS04 ~]# echo ${OLDBOY:2} # 截取前两个字节
am stephen
[root@CentOS04 ~]# echo ${OLDBOY:2:2} # 截取前两个字节并再输出两个字节
am
[root@CentOS04 ~]# echo ${OLDBOY}|cut -c 3-4 # 只输出第三到第四个字节
am
SHELL脚本批量修改文件名
[root@CentOS04 test]# for f in `cat a.log`;do touch $f;done
[root@CentOS04 test]# ll
total 4
-rw-r--r--. 1 root root 104 Jun 25 23:25 a.log
-rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_1_finished.jpg
-rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_2_finished.jpg
-rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_3_finished.jpg
-rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_4_finished.jpg
[root@CentOS04 test]# test="stu_102999_4_finished.jpg"
[root@CentOS04 test]# echo $test
stu_102999_4_finished.jpg
[root@CentOS04 test]# echo ${test}
stu_102999_4_finished.jpg
[root@CentOS04 test]# echo ${test%finished}
stu_102999_4_finished.jpg
[root@CentOS04 test]# echo ${test%finished*}
stu_102999_4_
[root@CentOS04 test]# echo ${test%finished*}.jpg
stu_102999_4_.jpg
[root@CentOS04 test]# vi piliangxiugai.sh
"piliangxiugai.sh" [New] 4L, 57C written
[root@CentOS04 test]# vi piliangxiugai.sh
for f in `ls *.jpg`
do
mv $f `echo ${f%finished*}.jpg`
done
"piliangxiugai.sh" 5L, 88C written
[root@CentOS04 test]# sh piliangxiugai.sh
stu_102999_1_.jpg
stu_102999_2_.jpg
stu_102999_3_.jpg
stu_102999_4_.jpg
使用rename改文件名
[root@CentOS04 test]# ll total 8 -rw-r--r--. 1 root root 104 Jun 25 23:25 a.log -rw-r--r--. 1 root root 85 Jun 26 00:09 piliangxiugai.sh -rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_1.jpg -rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_2.jpg -rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_3.jpg -rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_4.jpg [root@CentOS04 test]# rename .jpg .htm *.jpg [root@CentOS04 test]# ll total 8 -rw-r--r--. 1 root root 104 Jun 25 23:25 a.log -rw-r--r--. 1 root root 85 Jun 26 00:09 piliangxiugai.sh -rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_1.htm -rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_2.htm -rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_3.htm -rw-r--r--. 1 root root 0 Jun 25 23:25 stu_102999_4.htm
变量替换
[root@web01 test]# result=${test:-UNSET} # ${value:-word}，当变量未定义或者值为空时，返回值为word内容，否则返回变量的值。
[root@web01 test]# echo $result # result赋予UNSET，即使test未定义
UNSET
[root@web01 test]# echo $test # 由于test未定义，所以值依然为空
[root@web01 test]# unset $test
[root@web01 test]# tail -1 /etc/profile
export stephen="I am stephen"
[root@web01 test]# result=${stephen:-UNSET}
[root@web01 test]# echo $result # 由于stephen为全局变量，故result有值
I am stephen
[root@web01 test]# echo $stephen # stephen为全局变量
I am stephen
[root@web01 test]# unset result
[root@web01 test]# echo $result
[root@web01 test]# unset test
[root@web01 test]# echo $test
[root@web01 test]# result=${test:=UNSET} # ${value:=word}，当变量不存在时，会给变量赋于后面的内容
[root@web01 test]# echo $result
UNSET
[root@web01 test]# echo $test # test未定义，但会给其赋予后面的内容
UNSET
变量替换实际应用
[root@web01 test]# cat d.sh
path=/server/backup
find ${path:=/tmp} -name "*.tar.gz" -type f|xargs rm -f # 当变量path值存在时
[root@web01 test]# mkdir /server/backup -p
[root@web01 test]# sh -x d.sh
+ path=/server/backup
+ find /server/backup -name '*.tar.gz' -type f
+ xargs rm -f
[root@web01 test]# sed -i '1d' d.sh # 删除d.sh第一行内容
[root@web01 test]# cat d.sh
find ${path:=/tmp} -name "*.tar.gz" -type f|xargs rm -f # 当变量path没有值时，赋予其后面的值/tmp
[root@web01 test]# sh -x d.sh
+ find /tmp -name '*.tar.gz' -type f
+ xargs rm -f