Linuxshell编程学习笔记2.doc

Linux shell编程学习笔记（二）-chinaitlab linux学习视频2008-03-07 00:31第三章 shell的输入和输出1.echo echo option string -e 解析转移字符 -n 回车不换行，linux系统默认回车换行 转移字符 c t f n#!/bin/bash#echoecho -e this echos 3 newlnennnecho OKechoecho this is echos 3 ewlinennnecho this log file have all been donemylogfile.txttestszbirdora $ sh echod.shthis echos 3 newlneOKthis is echos 3 ewlinennn上面可以看到有-e则可以解析转移字符，没有不能解析。echo空输出为空2.read 可以从键盘或文件的某一行文本中读入信息，并将其赋给一个变量read variable1 variable2eg.#!/bin/bash#readnameecho -n first name:read firstnameecho -n last name:read lastnameecho this name is $firstname $lastname3.cat 显示文件的内容，创建内容，还可以显示控制字符 cat optionsfilename1 filename2 -v 显示控制字符（Windows文件） cat命令不会分页显示，要分页可以采用more、less4.管道|5.tee把输出的一个副本输送到标准输出，另一个副本拷贝到相应的文件中,一般与管道合用 tee options files -a 在文件中追加eg.testszbirdora 1$ echo |tee myfiletestszbirdora 1$ cat myfile将myfile文件置空6.文件重定向commandfilename -覆盖输出 commandfilename -追加输出commandfilename&1 -把标准输出和标准错误重定向commanddelimiter -输入直到delimiter分解符commandfilename-输入文件内容到命令commandnullfile.txt -创建字节为0的文件command1command3 -按从左到右顺序执行eg.说明：myfile为空间testszbirdora 1$ df -lhmyfiletestszbirdora 1$ cat myfileFilesystem Size Used Avail Use% Mounted on/dev/sda1 20G 3.3G 16G 18% /none 2.0G 0 2.0G 0% /dev/shm/dev/sda2 79G 17G 59G 23% /u01/dev/sda4 28G 3.9G 22G 15% /u02testszbirdora 1$ df -lhmyfiletestszbirdora 1$ cat myfileFilesystem Size Used Avail Use% Mounted on/dev/sda1 20G 3.3G 16G 18% /none 2.0G 0 2.0G 0% /dev/shm/dev/sda2 79G 17G 59G 23% /u01/dev/sda4 28G 3.9G 22G 15% /u02testszbirdora 1$ df -lhmyfiletestszbirdora 1$ cat myfileFilesystem Size Used Avail Use% Mounted on/dev/sda1 20G 3.3G 16G 18% /none 2.0G 0 2.0G 0% /dev/shm/dev/sda2 79G 17G 59G 23% /u01/dev/sda4 28G 3.9G 22G 15% /u02Filesystem Size Used Avail Use% Mounted on/dev/sda1 20G 3.3G 16G 18% /none 2.0G 0 2.0G 0% /dev/shm/dev/sda2 79G 17G 59G 23% /u01/dev/sda4 28G 3.9G 22G 15% /u02testszbirdora 1$ cat myfile China Hubei Suizhou exittestszbirdora 1$ cat myfileChinaHubeiSuizhou7.exec 可以用来替代当前shell。现有任何环境变量都会清除第四章 控制流结构1.if语句if 条件1then 命令1elif 条件2then 命令2else 命令3fi-if 条件then 命令fieg：#!/bin/bash#if test#this is a comment lineif 10 -lt 12 ;then#yes 10 is less than 12echo yes,10 is less than 12elseecho nofi注意：if语句必须以fi终止 10 前一个空格，“12”后也有一个空格。这个条件都是通过test命令来指定。条件表达为test expression或者expression条件表达式中的比较函数man testNAME test - check file types and compare valuesSYNOPSIS test EXPRESSION EXPRESSION OPTIONDESCRIPTION Exit with the status determined by EXPRESSION. -help display this help and exit -version output version information and exit EXPRESSION is true or false and sets exit status. It is one of: ( EXPRESSION ) EXPRESSION is true ! EXPRESSION EXPRESSION is false EXPRESSION1 -a EXPRESSION2 both EXPRESSION1 and EXPRESSION2 are true EXPRESSION1 -o EXPRESSION2 either EXPRESSION1 or EXPRESSION2 is true -n STRING the length of STRING is nonzero -z STRING the length of STRING is zero STRING1 = STRING2 the strings are equal STRING1 != STRING2 the strings are not equal INTEGER1 -eq INTEGER2 INTEGER1 is equal to INTEGER2 INTEGER1 -ge INTEGER2 INTEGER1 is greater than or equal to INTEGER2 INTEGER1 -gt INTEGER2 INTEGER1 is greater than INTEGER2 INTEGER1 -le INTEGER2 INTEGER1 is less than or equal to INTEGER2 INTEGER1 -lt INTEGER2 INTEGER1 is less than INTEGER2 INTEGER1 -ne INTEGER2 INTEGER1 is not equal to INTEGER2 FILE1 -ef FILE2 FILE1 and FILE2 have the same device and inode numbers FILE1 -nt FILE2 FILE1 is newer (modification date) than FILE2 FILE1 -ot FILE2 FILE1 is older than FILE2 -b FILE FILE exists and is block special -c FILE FILE exists and is character special -d FILE FILE exists and is a directory -e FILE FILE exists -f FILE FILE exists and is a regular file -g FILE FILE exists and is set-group-ID -h FILE FILE exists and is a symbolic link (same as -L) -G FILE FILE exists and is owned by the effective group ID -k FILE FILE exists and has its sticky bit set -L FILE FILE exists and is a symbolic link (same as -h) -O FILE FILE exists and is owned by the effective user ID -p FILE FILE exists and is a named pipe -r FILE FILE exists and is readable -s FILE FILE exists and has a size greater than zero -S FILE FILE exists and is a socket -t FD file descriptor FD (stdout by default) is opened on a terminal -u FILE FILE exists and its set-user-ID bit is set -w FILE FILE exists and is writable -x FILE FILE exists and is executableeg.#!/bin/bash#if test#this is a comment lineecho Enter your filename:read myfileif -e $myfile then if -s $myfile ;then echo $myfile exist and size greater than zero else echo $myfile exist but size is zero fielseecho file no existfitestszbirdora 1$ sh iftest.sh Enter your filename:1111 exist but size is zero2.case语句case语句为多选择语句。case 值 in模式1） 命令1 ;模式2) 命令2 ;esaceg.#!/bin/bash#case selectecho -n enter a number from 1 to 3:read anscase $ans in1)echo you select 1;2)echo you select 2;3)echo you select 3;*)echo basename $0:this is not between 1 and 3&2exit;esac3.for 循环for循环一般格式：for 变量名 in 列表 (列表以