一组Linux Shell Scripting小练习-阿里云开发者社区

一组Linux Shell Scripting小练习

2016-05-24 1557

版权

本文内容由阿里云实名注册用户自发贡献，版权归原作者所有，阿里云开发者社区不拥有其著作权，亦不承担相应法律责任。具体规则请查看《阿里云开发者社区用户服务协议》和《阿里云开发者社区知识产权保护指引》。如果您发现本社区中有涉嫌抄袭的内容，填写侵权投诉表单进行举报，一经查实，本社区将立刻删除涉嫌侵权内容。

简介：

原创作品，允许转载，转载时请务必以超链接形式标明文章原始出处、作者信息和本声明。否则将追究法律责任。 http://dgd2010.blog.51cto.com/1539422/1718284

# Linux shell将字符串分割成数组

 
         result=$(facter | 
         awk 
         '/ipaddress/ && !/ipaddress_lo/ {print $1 " " $3}'
         ) 
        
         array=($result)

# 判断一个变量是否存在（不是判断是否为空）

 
         if 
         [ -z ${var+x} ]; 
         then 
         echo 
         "var is unset"
         ; 
         else 
         echo 
         "var is set to '$var'"
         ; 
         fi

# 判断一个变量是否为空

 
   
     
       
       
         if 
         [ 
         "$var x" 
         = 
         " x" 
         ]; 
         then 
         echo 
         "var is empty"
         ; 
         else 
         echo 
         "var is set to '$var'"
         ; 
         fi 
        
 
         if 
         [ -z $var ]; 
         then 
         echo 
         "var is empty"
         ; 
         else 
         echo 
         "var is set to '$var'"
         ; 
         fi 
        
 
     

    
  

#系统变量用后还原

# 关于IFS的定义：IFS,Internal Field Separator

# An Internal Field Separator (IFS) is an environment variable that stores delimiting characters.

# It is the default delimiter string used by a running shell environment.

# "$*" expands as "$1c$2c$3", where c is the first character of IFS

# When the expansion occurs within double quotes, it expands to a single word with the value of each parameter separated by the first character of the IFS special variable.

# That is, "$*" is equivalent to "$1c$2c...", where c is the first char‐acter of the value of the IFS variable.

# If IFS is unset, the parameters are separated by spaces. If IFS is null, the parameters are joined without intervening separators.

 
         oldIFS=
         "$IFS" 
        
         IFS=
         " " 
        
         array=($result)
        
         IFS=
         "$oldIFS" 
        
         for 
         i 
         in 
         ${array[@]}; 
         do 
        
         echo 
         $i 
        
         done

# 使用facter获取一组key-value

# facter的输出有换行符，必须把换行符替换成空格

# 将换行符替换成空格可以使用awk或sed

# awk -v RS="" '{gsub("\n"," ");print}'

# echo -e "2 \n1" | sed ':a;N;$!ba;s/\n/ /g'

 
         result=$(facter | 
         awk 
         '/ipaddress/ && !/ipaddress_lo/ {print $1 " " $3}' 
         | 
         awk 
         -
         v 
         RS=
         "" 
         '{gsub("\n"," ");print}'
         ) 
        
         array=($result)
        
         array_length=${
         #array[@]}

# 输出key

 
         for 
         (( i = 0; i < $array_length; i=i+2 )); 
         do 
        
         echo 
         ${array[$i]} 
        
         done

# 输出value

 
         for 
         (( i = 1; i < $array_length; i=i+2 )); 
         do 
        
         echo 
         ${array[$i]} 
        
         done

# 输出key-value

 
         for 
         (( i = 0; i < $array_length; i=i+2 )); 
         do 
        
         j=$i+1 
        
         echo 
         "${array[$i]} - ${array[$j]}" 
        
         done