shell之脚本片断
14.删除程序产生的日志，只保留一个当天日期的文件，并且在每天20点时清空此文件，感觉有点重复，要么只保留一个文件，要么清空都可以达到减少占用磁盘的目的。
[Thu Mar 26 10:01:40 1071 /dev/pts/1 192.168.2.109 /usr/local/ps/log]#cat /var/prtg/scripts/pslog #find /usr/local/ps/log -ctime +0|xargs rm -rf #>/usr/local/ps/log/debug* a=debug`date +%Y%m%d`.log for i in `ls *.log` do if [ "$i" != "$a" ] then rm -rf $i else >$i fi done
13.
黑白棋盘
其实是个双循环，
外层执行第一层循环时
内层共执行8次，并判断是单或双，
是单的话，total是双，tmp余数是0，输出背景为灰的两个空格
是双的话，total是单，tmp余数是1，输出背景为黑的两个空格
外层第一层最后一个echo ""是换行
然后执行第二层外循环
[Wed Mar 25|15:40:23 ~ 1081 /bin/bash ]# cat black #!/bin/bash for((i=1;i<=8;i++)) do for((j=1;j<=8;j++)) do total=$(($i+$j)) tmp=$(($total%2)) if [ $tmp -eq 0 ] then echo -e -n "\033[47m \033[0m" else echo -e -n "\033[40m \033[0m" fi done echo "" done
[Wed Mar 25|15:40:46 ~ 1082 /bin/bash ]# cat .bashrc # .bashrc # User specific aliases and functions alias rm='rm -i' alias cp='cp -i' alias mv='mv -i' # Source global definitions if [ -f /etc/bashrc ]; then . /etc/bashrc fi #PS1='[\u@\h \W]\$ ' export PS1='[\d|\t \w \! $SHELL ]\$ '
12.
因为有好多的safe进程，所以把每一个列出来并杀死 [root@aster3 ~]# cat a a=`ps -ef|grep safe|grep -v grep|awk '{print $2}'` for i in $a do kill -9 $i done 清空每一个日志文件 [root@84-monitor monitorlog]# cat a for i in `ls *.log` do #echo $i > $i done
11.
日常工作中，处理数据难免会遇到遍历，for循环可能是我们用的比较多的了。本节就来探讨下for语句嵌套循环的性能，猜想下面两个语句的性能。 外层循环越少效率越高 [root@250-shiyan sh]# cat inlinefor for (( i=1; i<100; i++ )) do for (( c=1; c<1000; c++ )) do echo "$c-----inline" done echo "$i-----outline" done [root@250-shiyan sh]# cat outlinefor for (( i=1; i<1000; i++ )) do for (( c=1; c<100; c++ )) do echo "$c-----inline" done echo "$i-----outline" done [root@250-shiyan sh]# time (bash inlinefor) |tail -3 998-----inline 999-----inline 99-----outline real 0m1.754s user 0m1.433s sys 0m0.319s [root@250-shiyan sh]# time (bash outlinefor) |tail -3 98-----inline 99-----inline 999-----outline real 0m1.731s user 0m1.392s sys 0m0.338s [root@250-shiyan sh]# time (bash inlinefor) |tail -3 9998-----inline 9999-----inline 999-----outline real 3m8.818s user 2m25.615s sys 0m43.021s [root@250-shiyan sh]# time (bash outlinefor) |tail -3 998-----inline 999-----inline 9999-----outline real 3m5.233s user 2m21.791s sys 0m43.278s
10.脚本执行方式及子进程关系
###4种方式：全路径/path/to/conns|bash conns|source conns|. conns
###要有执行权限产生子shell
[root@250-shiyan prog]# cat conns #!/bin/bash ip_conns=`ssh $1 "netstat -ant| grep EST | wc -l"` echo $ip_conns [root@250-shiyan prog]# chmod u+x conns [root@250-shiyan prog]# cp conns /usr/bin [root@250-shiyan prog]# conns 192.168.2.109
[root@250-shiyan prog]# ./conns
[email protected]'s password:
851
###无需执行权限,产生子shell
[root@250-shiyan prog]# bash conns
[email protected]'s password:
855
[root@84-monitor ~]# cat a
a=192.168.2.109
ip_conns=`ssh $a "netstat -ant| grep EST | wc -l"`
echo $ip_conns
###source命令与点命令是在当前shell中执行，并不产生子shell，也不需要脚本有执行权限。
[root@84-monitor ~]# source a
860
[root@84-monitor ~]# . a
860
9.
shell 判断字符串中是否含有指定字符 new=sdd ps=s echo "$new" |grep -q "$ps" if [ $? -eq 0 ] then echo "yes" else echo "no" fi 判断某年某天是星期几？ year=1980 end_year=2010 day_2=10/22 week_2=Fri while [ $year -lt $end_year ] do new=`date -d "$day_2 CST $year"` echo "$new" echo "$new" |grep -q "$week_2" if [ $? -eq 0 ] then # year=`expr $year + 1` echo "this year $year include $week_2" year=`expr $year + 1` else #echo "this year $year include $week_2" year=`expr $year + 1` fi done
[root@250-shiyan prog]# expr length "$HOME"
5
[root@250-shiyan prog]# echo "$HOME"|wc -c
6
[root@250-shiyan prog]# echo “$HOME”|awk '{print length($0)}'
7
判断字符串为空的方法有三种： if [ "$str" = "" ] if [ x"$str" = x ] if [ -z "$str" ] （-n 为非空） 注意：都要用双引号，否则有些命令会报错，养成好习惯吧！
8.
[root@250-shiyan frag]# bash here.sh USAGE: xtitlebar [-h] "string_for_titelbar" OPTIONS: -h help text EXAMPLE: xtitlebar "cvs" [root@250-shiyan frag]# cat here.sh help() { cat <<HELP USAGE: xtitlebar [-h] "string_for_titelbar" OPTIONS: -h help text EXAMPLE: xtitlebar "cvs" HELP exit 0 } help
7.还有点问题，2015/5/25的时候才搞明白下面的问题所在。才理解了下面的这段脚本含义。
[root@250-shiyan frag]# bash while2.sh enter y/n : y =============================================== | unix script test | | 1 --- num 1 | | 2 --- num 2 | | 3 --- num 3 | | 4 --- num 4 | =============================================== enter y/n : n Press <return> to proceed or type q to quit: ef Press <return> to proceed or type q to quit: ef Press <return> to proceed or type q to quit: q [root@250-shiyan frag]# cat while2.sh #!/bin/bash banner() { cat <<echo1 =============================================== | unix script test | | 1 --- num 1 | | 2 --- num 2 | | 3 --- num 3 | | 4 --- num 4 | =============================================== echo1 } getyn() { while echo "enter y/n :" do read yn case $yn in [Yy]) return 0 ;; yes) return 0 ;; YES) return 0 ;; [Nn]) return 1 ;; no) return 1;; NO) return 1;; * ) echo "only accept Y,y,N,n,YES,yes,NO,no";; esac done } pause() { while echo "Press <return> to proceed or type q to quit:" do read cmd case $cmd in ####break跳出while语句 [qQ]) exit 1;; ####引号中间没有任何字符，表示是return "") break;; ####continue继续下一循环 *) continue;; esac done } ####pause or getyn to test while getyn do banner done pause
6.
[root@250-shiyan frag]# bash while.sh input num: 4 input is 4 new num is 5 new num is 6 new num is 7 new num is 8 new num is 9 new num is 10 [root@250-shiyan frag]# cat while.sh #!/bin/bash echo "input num:" read num echo "input is $num" while test $num -lt 10 do num=$(($num+1)) echo "new num is $num" sleep 2 done
5.
[root@localhost script]# cat >if-1 #!/bin/bash echo -e "are you ok(y/n or maybe)? \c" read answer if [[ $answer == [yY]* || $answer = maybe ]] then echo "glad to hear it" fi [root@localhost script]# bash if-1 are you ok(y/n or maybe)? dk [root@localhost script]# bash if-1 are you ok(y/n or maybe)? y glad to hear it [root@localhost script]# bash if-1 are you ok(y/n or maybe)? Y glad to hear it [root@localhost script]# bash if-1 are you ok(y/n or maybe)? maybe glad to hear it
4.||表示只要其中之一个，满足即可，&&表示两个，以至n个条件都要满足才可以。
####也可以一试
if [[ "$s" -gt "0" || "$r" -gt "0" ]]
[root@localhost script]# cat >if-2 #!/bin/bash echo -e "how old are you? \c" read age if (( age < 0 || age > 120 )) then echo "you are so old" ####两个同时满足，即上限与下限 elif (( age >=0 && age <= 12 )) then echo "you are child" elif (( age >=13 && age <=19 )) then echo "you are 13-19 years old" elif (( age >=20 && age <=29 )) then echo "you are 20-29 years old" elif (( age >=30 && age <=39 )) then echo "you are 30-39 years old" else echo "you are above 40" fi [root@localhost script]# bash if-2 how old are you? 30 you are 30-39 years old [root@localhost script]# bash if-2 how old are you? 28 you are 20-29 years old [root@localhost script]# bash if-2 how old are you? 400 you are so old [root@localhost script]# bash if-2 how old are you? 0 you are child
3.检查根分区，循环做两件事，a.输出当前值，b.如果大于10%，则输出信息
[root@250-shiyan sh]# cat check-root.sh #!/bin/bash while sleep 5 do for i in `df -h |sed -n '/\/$/p'|awk '{print $5}'|sed 's/\%//g'` do echo $i if [ $i -ge 10 ] then echo " more than 10$ linux of disk space." fi done done [root@250-shiyan sh]# bash check-root.sh 11 more than 10$ linux of disk space. 11 more than 10$ linux of disk space.
2.自编有while循环，有函数，有if，还有脚本参数，执行时 ./while w1或./while w2
[root@250-shiyan sh]# cat while #!/bin/bash w1 () { min=1 max=100 while [ $min -le $max ] do echo $min min=`expr $min + 1` done } w2 () { i=1 while(($i<100)) do if(($i%4==0)) then echo $i fi i=$(($i+1)) done } if [ $@ = w1 ] then w1 else w2 fi
1.自编让其以后台进程形式存在，不用crontab去定期执行
[root@250-shiyan sh]# cat eth #!/bin/bash while [ 1 -gt 0 ] do eth=`ifconfig eth0|grep "TX bytes"|gawk '{print $6}'|cut -d ":" -f2` echo $eth >> /root/sh/jj sleep 2 done [root@250-shiyan sh]# bash eth & [root@250-shiyan sh]# tail -f jj