Linux命令行和shell腳本編程的示例分析

小編給大家分享一下Linux命令行和shell腳本編程的示例分析，相信大部分人都還不怎么了解，因此分享這篇文章給大家參考一下，希望大家閱讀完這篇文章后大有收獲，下面讓我們一起去了解一下吧！

第一個腳本文件

代碼如下:

#!/bin/bash
echo "This is my first bash code!"
exit 0

重定向符號和數學計算

代碼如下:

#!/bin/bash
echo -n "The time and date are: "
date
value1=100  #等號前后不允許出現空格
value2=$value1
echo -n "value1="
echo $value1
echo -n "value2="
echo $value2
ls -l | sort > out.txt   #管道符號(|)和重定向輸出符號>
ls -l >> out.txt   #重定向追加輸出符號>>
echo -n  "wc<out.txt:"
wc < out.txt  #重定向輸入符號<
echo "sort<<EOF ... EOF"
sort << EOF  #內置輸入重定向<<
`date`
EOF
#數學計算
echo -n "expr進行計算：1+5="
expr 1+5
echo -n "使用方括號進行計算：1+5="
echo $[1+5]
echo "使用bc計算器進行浮點運算"
var1=100
var2=200
var3=`echo "scale=4;$var1/$var2" | bc`
echo "$var1 / $var2 = $var3"
var4=71
var5=`bc<<EOF
scale=4
a1=($var1*$var2)
b1=($var3*$var4)
a1+b1
EOF`
echo "var5=$var5"
exit 0

使用test命令

代碼如下:

#!/bin/bash
#使用test命令
var1=10
var2=100
if [ $var1 -gt $var2 ]
then
    echo "var1 grate var2"
else
    echo "var2 grate var1"
fi
#只能比較整數
test_user=hanxi
if [ $USER = $test_user ]
then
    echo "Welcome $test_user"
fi
str1=Hanxi
str2=hanxi
if [ $str1 \> $str2 ]
then
    echo "$str1 > $str2"
else
    echo "$str1 < $str2"
fi
if [ -n $str1 ]
then
    echo "The string '$str1' is not empty"
else
    echo "the string '$str1' is empty"
fi
#檢查文件目錄
if [ -d $HOME ]
then
    echo "your Home dir exists"
    cd $HOME
    ls -a
else
    echo "there's a problem with your HOME dir"
fi
pwfile=/etc/shadow
if [ -f $pwfile ]
then
    if [ -r $pwfile ]
    then
        tail $pwfile
    else
        echo "Sorry, I'm unable to reas the $pwfile file "
    fi
else
    echo "Sorry, the file $pwfile doesn't exist"
fi
if [[ $USER == h* ]]
then
    echo "Hello $USER"
else
    echo "Sorry, I don't know you"
fi

循環語句

代碼如下:

#!/bin/bash
for file in /home/hanxi/*
do
    if [ -d "$file" ]
    then
        echo "$file is a directory"
    elif [ -f "$file" ]
    then
        echo "$file is a file"
    fi
done
var1=10
while [ $var1 -gt 0 ]
do
    echo $var1
    var1=$[ $var1 - 1 ]
done
var1=100
until [ $var1 -eq 0 ]
do
    echo $var1
    var1=$[ $var1 - 25 ]
done
#文件數據的循環
IFSOLD=$IFS
IFS=$'\n'
for entry in `cat /etc/passwd`
do
    echo "Values in $entry -"
    IFS=:
    for value in $entry
    do
        echo " $value"
    done
done | more
for file in /home/hanxi/*
do
    if [ -d "$file" ]
    then
        echo "$file is directory"
    elif
        echo "$file is a file"
    fi
done > output.txt

讀取參數

代碼如下:

#!/bin/bash
name=`basename $0`
echo the commane entered is : $name
c_args=$#
echo count args:$c_args
#取最后一個參數
echo the last parameter is ${!#}
echo all parameter: $*
echo all parameter: $@
count=1
for param in "$@"
do
    echo "\$@ parameter #$count = $param"
    count=$[ $count + 1 ]
done
#getopts
while getopts :ab:c opt
do
    case "$opt" in
    a) echo "Found the -a option";;
    b) echo "Found the -b option, with value $OPTARG";;
    c) echo "Found the -c option";;
    *) echo "Unknown option : $opt";;
    esac
done
shift $[ $OPTIND - 1 ]
count=1
for param in "$@"
do
    echo "Parameter $count: $param"
    count=$[ $count + 1 ]
done
read -p "Please enter your age:" age
echo age:$age
if read -t 5 -p "Please enter your name: " name
then
    echo "Hellp $name,welcome to my script"
else
    echo
    echo "sorry ,too slow!"
fi
read -n1 -p "Do you want to continue [Y/N]?" answer
case $answer in
Y | y) echo
       echo " fine, continue on...";;
N | n) echo
       echo OK,Good bye
       exit;;
esac
echo "This is the end of the script"
read -s -p "Enter your password: " pass
echo
echo "Is your password really $pass?"
#讀取文件
count=1
cat for.txt | while read line
do
    echo "Line $count: $line"
    count=$[ $count+1 ]
done
echo "Finished processing the file"

重定向文件描述符

代碼如下:

#!/bin/bash
#永久重定向
exec 9>&2
exec 2>testerror
echo "this will in testerror">&2
exec 2<&9
exec 9<&0
exec 0<testin
count=1
while read line
do
    echo "Line #$count:$line"
    count=$[ $count + 1 ]
done
exec 0<&9
#重定向文件描述符
exec 3>&1
exec 1>testout
echo "this should store in the output file"
echo "along with this line."
exec 1>&3
echo "Now things should be back to nomarl"
exec 4<&0
exec 0<testin
count=1
while read line
do
    echo "Line #$count:$line"
    count=$[ $count + 1 ]
done
exec 0<&4
read -p "Are you done now?" answer
case $answer in
Y|y) echo "Goodbye";;
N|n) echo "continue...";
esac
#創建讀寫文件描述符
exec 8<> testfile
read line <&8
echo "Read:$line"
echo "This is a test line" >&8
#關閉文件描述符
exec 8>&-
#列出文件描述服
#`/usr/sbin/lsof -a -p $$`|more
#禁止命令輸出
#2 > /dev/null
#創建本地臨時文件
tempfile=`mktemp test.XXXXXX`
exec 4>$tempfile
echo "This is the first line">&3
exec 4>&-
#在/temp中創建臨時文件
tmpfile=`mktemp -t tmp.XXXXXX`
echo "The temp file is located at:$tempfile"
cat $tempfile
rm -f $tempfile
#創建臨時文件夾
tmpdir=`mktemp -d dir.XXXXXX`
cd $tmpdir
tempfile1=`mktemp temp.XXXXXX`
ls -l
cd ..
#記錄消息
a=`date | tee testfile;\
cat testfile;\
date | tee -a testfile;\
cat testfile`

信號處理

代碼如下:

#!/bin/bash
#信號處理
trap "echo 'get a sign'" SIGINT SIGTERM
trap "echo byebye" EXIT
echo "This is a test program"
count=1
while [ $count -le 10 ]
do
    echo "Loop #$count"
    sleep 10
    count=$[ $count+1 ]
done
echo "This is the end of the test program"
trap - EXIT#移除捕獲
#后臺牧師運行
#./test6.sh &
#不使用終端的情況下運行腳本
#nohup ./test6.sh &
#查看作業
#jobs
#重新啟動作業
#bg 2(作業序號)//后臺
#fg 2//前臺
#優先級
#nice -n 10 ./test6.sh
#renice 10 -p 25904(進程號)
#預計時間運行at命令
#at -f test6.sh 20:00
#batch命令，系統平均負載低于0.8時運行，可以設定時間，比at命令更好
#corn表格可以設定循環運行,格式：
#min hour dayofmonth month dayofweek command
#每個月第一天運行：
#12 16 * * 1 command
#每個月最后一天運行：
#12 16 * * * if [ `date +%d =d tommorrow` = 01 ] ; then ; command

函數的使用

代碼如下:

#!/bin/bash
#函數
#使用返回值
function func1
{
    read -p "Enter a value: " value
    echo $[ $value * 2 ]
}
result=`func1`
echo "the new value is $result"
#傳遞參數
function func2
{
    echo $[ $1+$2 ]
}
result=`func2 2 2`
echo "the new result is $result"
#局部變量, 遞歸
function func3
{
    if [ $1 -eq 1 ]
    then
        echo 1
    else
        local temp=$[ $1-1 ]
        local result=`func3 $temp`
        echo $[ $result*$1 ]
    fi
}
read -p "Enter value:" value
result=`func3 $value`
echo "the factorial of $value is: $result"
#調用當前目錄下到函數庫
#. ./myfuncs

以上是“Linux命令行和shell腳本編程的示例分析”這篇文章的所有內容，感謝各位的閱讀！相信大家都有了一定的了解，希望分享的內容對大家有所幫助，如果還想學習更多知識，歡迎關注億速云行業資訊頻道！