shell_tutorial
Posted 步摇流苏
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$ echo ‘#!/bin/sh‘ > my-script.sh $ echo ‘echo Hello World‘ >> my-script.sh $ chmod 755 my-script.sh $ ./my-script.sh Hello World $
上面这段代码中，echo是打印的意思，而>是重定向的意思，chmod是修改权限的意思。shell脚本以.sh为结尾。
#!/bin/sh # This is a comment! echo Hello World # This is a comment, too!
以上为my-script.sh中的代码，可以学习一下如何写注释。
$ chmod a+rx my-script.sh
$ ./my-script.sh
想要将shell脚本变成可执行的，可以使用以上语句。
grep "mystring" /tmp/myfile
这句的意思是将在/tmp/myfile中的"mystring"字符串搜索出来。
#!/bin/sh # This is a comment! echo Hello World # This is a comment, too!
以上是first.sh中的代码。可以使用以下代码执行：
$ chmod 755 first.sh $ ./first.sh Hello World $
得到结果：
$ echo Hello World Hello World $ #!/bin/sh MY_MESSAGE="Hello World" echo $MY_MESSAGE
以上是var.sh的代码。用来学习变量的使用。环境变量使用以下代码实现：
$ export name=zuoyuan #!/bin/sh echo What is your name? read MY_NAME echo "Hello $MY_NAME - hope you‘re well."
以上是var2.sh的代码。
#!/bin/sh echo "What is your name?" read USER_NAME echo "Hello $USER_NAME" echo "I will create you a file called ${USER_NAME}_file" touch "${USER_NAME}_file"
以上代码可以创建一个文件，touch关键字的作用是如果有这个文件，不做任何操作，如果没有这个文件，就创建一个这个文件。
#!/bin/sh for i in 1 2 3 4 5 do echo "Looping ... number $i" done
以上是for循环。写入for.sh。
#!/bin/sh for i in hello 1 * 2 goodbye do echo "Looping ... i is set to $i" done
继续for循环。写入for2.sh中。
#!/bin/sh INPUT_STRING=hello while [ "$INPUT_STRING" != "bye" ] do echo "Please type something in (bye to quit)" read INPUT_STRING echo "You typed: $INPUT_STRING" done
while循环。
#!/bin/sh while : do echo "Please type something in (^C to quit)" read INPUT_STRING echo "You typed: $INPUT_STRING" done
继续while循环。
#!/bin/sh while read f do case $f in hello) echo English ;; howdy) echo American ;; gday) echo Australian ;; bonjour) echo French ;; "guten tag") echo German ;; *) echo Unknown Language: $f ;; esac done < myfile
使用while循环读取文件。
for runlevel in 0 1 2 3 4 5 6 S do mkdir rc${runlevel}.d done
批量建文件。
if [ ... ] then # if-code else # else-code fi if [ ... ]; then # do something fi if [ something ]; then echo "Something" elif [ something_else ]; then echo "Something else" else echo "None of the above" fi
以上是几种条件结构。
#!/bin/sh if [ "$X" -lt "0" ] then echo "X is less than zero" fi if [ "$X" -gt "0" ]; then echo "X is more than zero" fi [ "$X" -le "0" ] && echo "X is less than or equal to zero" [ "$X" -ge "0" ] && echo "X is more than or equal to zero" [ "$X" = "0" ] && echo "X is the string or number "0"" [ "$X" = "hello" ] && echo "X matches the string "hello"" [ "$X" != "hello" ] && echo "X is not the string "hello"" [ -n "$X" ] && echo "X is of nonzero length" [ -f "$X" ] && echo "X is the path of a real file" || echo "No such file: $X" [ -x "$X" ] && echo "X is the path of an executable file" [ "$X" -nt "/etc/passwd" ] && echo "X is a file which is newer than /etc/passwd" echo -en "Please guess the magic number: " read X echo $X | grep "[^0-9]" > /dev/null 2>&1 if [ "$?" -eq "0" ]; then # If the grep found something other than 0-9 # then it‘s not an integer. echo "Sorry, wanted a number" else # The grep found only 0-9, so it‘s an integer. # We can safely do a test on it. if [ "$X" -eq "7" ]; then echo "You entered the magic number!" fi fi #!/bin/sh X=0 while [ -n "$X" ] do echo "Enter some text (RETURN to quit)" read X echo "You said: $X" done #!/bin/sh X=0 while [ -n "$X" ] do echo "Enter some text (RETURN to quit)" read X if [ -n "$X" ]; then echo "You said: $X" fi done if [ "$X" -lt "0" ] then echo "X is less than zero" fi .......... and ........ if [ ! -n "$X" ]; then echo "You said: $X" fi
以上是几个条件结构的例子。
继续举几个例子。
#!/bin/sh echo "Please talk to me ..." while : do read INPUT_STRING case $INPUT_STRING in hello) echo "Hello yourself!" ;; bye) echo "See you again!" break ;; *) echo "Sorry, I don‘t understand" ;; esac done echo echo "That‘s all folks!"
运行后有以下结果。
$ ./talk.sh Please talk to me ... hello Hello yourself! What do you think of politics? Sorry, I don‘t understand bye See you again! That‘s all folks! $
继续学习变量。以下代码写入var3.sh。
#!/bin/sh echo "I was called with $# parameters" echo "My name is $0" echo "My first parameter is $1" echo "My second parameter is $2" echo "All parameters are [email protected]"
运行结果如下：
$ /home/steve/var3.sh I was called with 0 parameters My name is /home/steve/var3.sh My first parameter is My second parameter is All parameters are $ $ ./var3.sh hello world earth I was called with 3 parameters My name is ./var3.sh My first parameter is hello My second parameter is world All parameters are hello world earth
继续学习变量。以下代码写入var4.sh。
#!/bin/sh while [ "$#" -gt "0" ] do echo "$1 is $1" shift done
This script keeps on using shift until $# is down to zero, at which point the list is empty. Another special variable is $?. This contains the exit value of the last run command. So the code:
#!/bin/sh /usr/local/bin/my-command if [ "$?" -ne "0" ]; then echo "Sorry, we had a problem there!" fi
当进程退出时的代码为0时，就没有问题。
#!/bin/sh old_IFS="$IFS" IFS=: echo "Please input some data separated by colons ..." read x y z IFS=$old_IFS echo "x is $x y is $y z is $z"
写入var5.sh。运行如下：
$ ./ifs.sh Please input some data separated by colons ... hello:how are you:today x is hello y is how are you z is today $ ./ifs.sh Please input some data separated by colons ... hello:how are you:today:my:friend x is hello y is how are you z is today:my:friend
使用默认变量。
#!/bin/sh echo -en "What is your name [ `whoami` ] " read myname if [ -z "$myname" ]; then myname=`whoami` fi echo "Your name is : $myname"
函数的用法。
#!/bin/sh # A simple script with a function... add_a_user() { USER=$1 PASSWORD=$2 shift; shift; # Having shifted twice, the rest is now comments ... COMMENTS=[email protected] echo "Adding user $USER ..." echo useradd -c "$COMMENTS" $USER echo passwd $USER $PASSWORD echo "Added user $USER ($COMMENTS) with pass $PASSWORD" } ### # Main body of script starts here ### echo "Start of script..." add_a_user bob letmein Bob Holness the presenter add_a_user fred badpassword Fred Durst the singer add_a_user bilko worsepassword Sgt. Bilko the role model echo "End of script..."
阶乘的shell实现，使用递归。
#!/bin/sh factorial() { if [ "$1" -gt "1" ]; then i=`expr $1 - 1` j=`factorial $i` k=`expr $1 * $j` echo $k else echo 1 fi } while : do echo "Enter a number:" read x factorial $x done
模块化编程。以下代码写入common.lib。
# common.lib # Note no #!/bin/sh as this should not spawn # an extra shell. It‘s not the end of the world # to have one, but clearer not to. # STD_MSG="About to rename some files..." rename() { # expects to be called as: rename .txt .bak FROM=$1 TO=$2 for i in *$FROM do j=`basename $i $FROM` mv $i ${j}$TO done }
以下代码写入function2.sh。
#!/bin/sh # function2.sh . ./common.lib echo $STD_MSG rename .txt .bak
返回码。
#!/bin/sh adduser() { USER=$1 PASSWORD=$2 shift ; shift COMMENTS=[email protected] useradd -c "${COMMENTS}" $USER if [ "$?" -ne "0" ]; then echo "Useradd failed" return 1 fi passwd $USER $PASSWORD if [ "$?" -ne "0" ]; then echo "Setting password failed" return 2 fi echo "Added user $USER ($COMMENTS) with pass $PASSWORD" } ## Main script starts here adduser bob letmein Bob Holness from Blockbusters ADDUSER_RETURN_CODE=$? if [ "$ADDUSER_RETURN_CODE" -eq "1" ]; then echo "Something went wrong with useradd" elif [ "$ADDUSER_RETURN_CODE" -eq "2" ]; then echo "Something went wrong with passwd" else echo "Bob Holness added to the system." fi
crontab的使用
在考虑向cron进程提交一个crontab文件之前，首先要做的一件事情就是设置环境变量EDITOR。cron进程根据它来确定使用哪个编辑器编辑crontab文件。9 9 %的UNIX和LINUX用户都使用vi，如果你也是这样，那么你就编辑$ HOME目录下的. profile文件，在其中加入这样一行：
EDITOR=vi; export EDITOR
然后保存并退出。不妨创建一个名为<user>cron的文件，其中<user>是用户名，例如，davecron。在该文件中加入如下的内容。
# (put your own initials here)echo the date to the console every # 15minutes between 6pm and 6am 0,15,30,45 18-06 * * * /bin/echo ‘date‘ > /dev/console
保存并退出。确信前面5个域用空格分隔。
在上面的例子中，系统将每隔1 5分钟向控制台输出一次当前时间。如果系统崩溃或挂起，从最后所显示的时间就可以一眼看出系统是什么时间停止工作的。在有些系统中，用tty1来表示控制台，可以根据实际情况对上面的例子进行相应的修改。为了提交你刚刚创建的crontab文件，可以把这个新创建的文件作为cron命令的参数：
$ crontab davecron
现在该文件已经提交给cron进程，它将每隔15分钟运行一次。
同时，新创建文件的一个副本已经被放在/var/spool/cron目录中，文件名就是用户名(即dave)。
为了列出crontab文件，可以用：
$ crontab -l
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