shell编程系列18--文本处理三剑客之awk动做中的条件及if/while/do while/for循环语句

时间  2019-12-05
标签 shell 编程 系列 文本 处理 剑客 awk 条件 循环 语句 栏目 Unix 繁體版
原文   原文链接 
shell编程系列18--文本处理三剑客之awk动做中的条件及if/while/do while/for循环语句
条件语句

    if(条件表达式)
        动做1
    else if(条件表达式)
        动做2
    else
        动做3


循环语句：
    while循环：
    while(条件表达式)
        动做


    do while循环:
        do
            动做
        while(条件表达式)
    

    for循环:
        for(初始化计数器;计数器测试;计数器变动)
            动做


    1、以:为分隔符，只打印/etc/passwd中第3个字段的数值在50-100范围内的行信息
        # 简单运算符处理
        awk 'BEGIN{FS=":"}{if($3>50 && $3<100) print $0}' passwd

        # if 条件处理
        # 输出 以 UID 以50位为分界点的用户，-f 将条件表达式写到文本中读取
        [root@localhost shell]# awk -f if.awk passwd 
        UID<50              root                0         
        UID<50              bin                 1         
        UID<50              daemon              2         
        UID<50              adm                 3         
        UID<50              lp                  4         
        UID<50              sync                5         
        UID<50              shutdown            6         
        UID<50              halt                7         
        UID<50              mail                8         
        UID<50              operator            11        
        UID<50              games               12        
        UID<50              ftp                 14        
        50<UID<100          nobody              99        
        UID>100             systemd-network     192       
        50<UID<100          dbus                81        
        UID>100             polkitd             999       
        50<UID<100          sshd                74        
        50<UID<100          postfix             89        
        UID>100             ajie                1000      
        UID>100             chrony              998       
        UID>100             deploy              1001      
        UID>100             nginx               997       
        [root@localhost shell]# cat if.awk 
        BEGIN{
            FS=":"
        }
        {
            if($3<50)
            {
                printf "%-20s%-20s%-10d\n","UID<50",$1,$3
            }
            else if ($3>50 && $3<100)
            {
                printf "%-20s%-20s%-10d\n","50<UID<100",$1,$3
            }
            else 
            {
                printf "%-20s%-20s%-10d\n","UID>100",$1,$3
            }
        }


    2、计算下列每一个同窗的平均分数，而且只打印平均分数大于90的同窗姓名和分数信息
        Allen    80    90    96    98
        Mike    93    98    92    91
        Zhang    78    76    87    92
        Jerry    86    89    68    92
        Han    85    95    75    90
        Li    78    88    98    100
        
        # 算出平均成绩 
        [root@localhost shell]# awk 'BEGIN{printf "%-20s%-20s%-20s%-20s%-20s%-20s\n","Name","Chinese","English","Math","Physical","Average"}{sum=$2+$3+$4+$5;avg=sum/4}{printf "%-20s%-20d%-20d%-20d%-20d%-0.2f\n",$1,$2,$3,$4,$5,avg}' student.txt 
        Name                Chinese             English             Math                Physical            Average             
        Allen               80                  90                  96                  98                  91.00
        Mike                93                  98                  92                  91                  93.50
        Zhang               78                  76                  87                  92                  83.25
        Jerry               86                  89                  68                  92                  83.75
        Han                 85                  95                  75                  90                  86.25
        Li                  78                  88                  98                  100                 91.00
        # 加入条件判断，若是平均分数大于90才打印
        [root@localhost shell]# awk 'BEGIN{printf "%-20s%-20s%-20s%-20s%-20s%-20s\n","Name","Chinese","English","Math","Physical","Average"}{sum=$2+$3+$4+$5;avg=sum/4}{if(avg>90) printf "%-20s%-20d%-20d%-20d%-20d%-0.2f\n",$1,$2,$3,$4,$5,avg}' student.txt 
        Name                Chinese             English             Math                Physical            Average             
        Allen               80                  90                  96                  98                  91.00
        Mike                93                  98                  92                  91                  93.50
        Li                  78                  88                  98                  100                 91.00

    3、计算1+2+3+4+...+100的和，请使用while、do while、for三种循环方式实现
        经过读取文件的方式载入awk的条件

        # while循环
        [root@localhost shell]# cat add_while.awk 
        BEGIN{
            while(i<=100)
            {
                # 一个变量不赋值，默认为0或者空
                sum+=i
                i++
            }    
            print sum
        }

        # do while循环
        [root@localhost shell]# awk -f add_dowhile.awk 
        5050
        [root@localhost shell]# cat add_dowhile.awk 
        BEGIN{
            do {
                sum+=i
                i++
            }while(i<=100)
            print sum
        }
        
        # for循环
        [root@localhost shell]# awk -f add_for.awk 
        5050
        [root@localhost shell]# cat add_for.awk 
        BEGIN{
            for(i=0;i<=100;i++) 
            {
                sum+=i
            }
            print sum
        }


# uid在50和100之间
[root@localhost shell]# awk 'BEGIN{FS=":"}{if($3>50 && $3<100) print $0}' passwd 
# uid小于50或者大于100
[root@localhost shell]# awk 'BEGIN{FS=":"}{if($3<50 || $3>100) print $0}' passwd 

[root@localhost shell]# awk 'BEGIN{FS=":"}{if($3<50){printf "%-30s%-30s%-15d\n","小于50的UID",$1,$3} else if($3>50 && $3<100) {printf "%-30s%-30s%-15d\n","大于50而且小于100的UID",$1,$3} else {printf "%-30s%-30s%-15d\n","大于100的UID",$1,$3}}' passwd 
小于50的UID                      root                          0              
小于50的UID                      bin                           1              
小于50的UID                      daemon                        2              
小于50的UID                      adm                           3              
小于50的UID                      lp                            4              
小于50的UID                      sync                          5              
小于50的UID                      shutdown                      6              
小于50的UID                      halt                          7              
小于50的UID                      mail                          8              
小于50的UID                      operator                      11             
小于50的UID                      games                         12             
小于50的UID                      ftp                           14             
大于50而且小于100的UID               nobody                        99             
大于100的UID                     systemd-network               192            
大于50而且小于100的UID               dbus                          81             
大于100的UID                     polkitd                       999            
大于50而且小于100的UID               sshd                          74             
大于50而且小于100的UID               postfix                       89             
大于100的UID                     ajie                          1000           
大于100的UID                     chrony                        998            
大于100的UID                     deploy                        1001           
大于100的UID                     nginx                         997 

# awk 经过-f参数读取文件的方式读取条件进行输出
[root@localhost shell]# cat scripts.awk 
BEGIN{
    FS=":"
}

{
    if($3<50)
    {
        printf "%-20s%-30s%-5d\n","UID<50",$1,$3
    }
    else if ($3>50 && $3<100)
    {
        printf "%-20s%-30s%-5d\n","50<UID<100",$1,$3
    }
    else
    {
        printf "%-20s%-30s%-5d\n","UID>100",$1,$3
    }
}
[root@localhost shell]# awk  -f scripts.awk passwd 
UID<50              root                          0    
UID<50              bin                           1    
UID<50              daemon                        2    
UID<50              adm                           3    
UID<50              lp                            4    
UID<50              sync                          5    
UID<50              shutdown                      6    
UID<50              halt                          7    
UID<50              mail                          8    
UID<50              operator                      11   
UID<50              games                         12   
UID<50              ftp                           14   
50<UID<100          nobody                        99   
UID>100             systemd-network               192  
50<UID<100          dbus                          81   
UID>100             polkitd                       999  
50<UID<100          sshd                          74   
50<UID<100          postfix                       89   
UID>100             ajie                          1000 
UID>100             chrony                        998  
UID>100             deploy                        1001 
UID>100             nginx                         997  
[root@localhost shell]# 


循环语句-do while

do while
do
    动做
while(条件表达式)

循环语句-for

for
for(初始化计数器;测试计数器;计数器变动)
    动做


# while循环
[root@localhost shell]# cat while.awk 
BEGIN{
    while(i<=100)
    {
        sum+=i
        i++
    }
    print sum
}
[root@localhost shell]# awk -f while.awk 
5050

# for循环
[root@localhost shell]# cat for.awk 
BEGIN{
    for(i=0;i<=100;i++)
    {
        sum+=i
    }
    print sum
}
[root@localhost shell]# awk -f for.awk 
5050

# do while循环
[root@localhost shell]# cat dowhile.awk 
BEGIN{
    do
    {
        sum+=i
        i++    
    }while(i<=100)
    print sum
}
[root@localhost shell]# awk -f dowhile.awk 
5050


[root@localhost shell]# cat student.txt
Name    chinese    english    math    physical    average
Allen    80    90    96    98
Mike    93    98    92    91
Zhang    78    76    87    92
Jerry    86    89    68    92
Han    85    95    75    90
Li    78    88    98    100


# 打印平均分大于90的人，并计算出各科总分
[root@localhost shell]# cat student.txt 
Allen    80    90    96    98
Mike    93    98    92    91
Zhang    78    76    87    92
Jerry    86    89    68    92
Han    85    95    75    90
Li    78    88    98    100
[root@localhost shell]# cat student.awk 
BEGIN{
    printf "%-10s%-10s%-10s%-10s%-10s%-10s\n","Name","Chinese","English","Math","Physical","Average"
}

{
    total=$2+$3+$4+$5
    avg=total/4
    if(avg>90)
    {
        printf "%-10s%-10d%-10d%-10d%-10d%-0.2f\n",$1,$2,$3,$4,$5,avg
        # 将每一科的成绩累加起来保存在一个变量中
        score_chinese+=$2
        score_english+=$3
        score_math+=$4
        score_physical=$5
    }
}
END{
    printf "%-10s%-10d%-10d%-10d%-10d\n","Name",score_chinese,score_english,score_math,score_physical
}
[root@localhost shell]# awk -f student.awk student.txt 
Name      Chinese   English   Math      Physical  Average   
Allen     80        90        96        98        91.00
Mike      93        98        92        91        93.50
Li        78        88        98        100       91.00
Name      251       276       286       100
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