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

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

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

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

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

    for循环:
        for(初始化计数器;计数器测试;计数器变更)
            动作

    、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<              root
        UID<              bin
        UID<              daemon
        UID<              adm
        UID<              lp
        UID<              sync
        UID<              shutdown
        UID<              halt
        UID<              mail
        UID<              operator
        UID<              games
        UID<              ftp
        <UID<          nobody
        UID>             systemd-network
        <UID<          dbus
        UID>             polkitd
        <UID<          sshd
        <UID<          postfix
        UID>             ajie
        UID>             chrony
        UID>             deploy
        UID>             nginx
        [root@localhost shell]# cat if.awk
        BEGIN{
            FS=":"
        }
        {
            if($<)
            {
                printf "%-20s%-20s%-10d\n","UID<50",$,$
            }
            else if ($> && $<)
            {
                printf "%-20s%-20s%-10d\n","50<UID<100",$,$
            }
            else
            {
                printf "%-20s%-20s%-10d\n","UID>100",$,$
            }
        }

    、计算下列每个同学的平均分数，并且只打印平均分数大于90的同学姓名和分数信息
        Allen
        Mike
        Zhang
        Jerry
        Han
        Li                

        # 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                                                                                       91.00
        Mike                                                                                        93.50
        Zhang                                                                                       83.25
        Jerry                                                                                       83.75
        Han                                                                                         86.25
        Li                                                                                         91.00
        # 加入条件判断，如果平均分数大于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                                                                                       91.00
        Mike                                                                                        93.50
        Li                                                                                         91.00

    、计算1++++...+100的和，请使用while、do while、for三种循环方式实现
        通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<=)
            {
                # 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 

        [root@localhost shell]# cat add_dowhile.awk
        BEGIN{
            do {
                sum+=i
                i++
            }while(i<=)
            print sum
        }

        # for循环
        [root@localhost shell]# awk -f add_for.awk 

        [root@localhost shell]# cat add_for.awk
        BEGIN{
            for(i=;i<=;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并且小于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
小于50的UID                      bin
小于50的UID                      daemon
小于50的UID                      adm
小于50的UID                      lp
小于50的UID                      sync
小于50的UID                      shutdown
小于50的UID                      halt
小于50的UID                      mail
小于50的UID                      operator
小于50的UID                      games
小于50的UID                      ftp
大于50并且小于100的UID               nobody
大于100的UID                     systemd-network
大于50并且小于100的UID               dbus
大于100的UID                     polkitd
大于50并且小于100的UID               sshd
大于50并且小于100的UID               postfix
大于100的UID                     ajie
大于100的UID                     chrony
大于100的UID                     deploy
大于100的UID                     nginx                          

# awk 通过-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($<)
    {
        printf "%-20s%-30s%-5d\n","UID<50",$,$
    }
    else if ($> && $<)
    {
        printf "%-20s%-30s%-5d\n","50<UID<100",$,$
    }
    else
    {
        printf "%-20s%-30s%-5d\n","UID>100",$,$
    }
}
[root@localhost shell]# awk  -f scripts.awk passwd
UID<              root
UID<              bin
UID<              daemon
UID<              adm
UID<              lp
UID<              sync
UID<              shutdown
UID<              halt
UID<              mail
UID<              operator
UID<              games
UID<              ftp
<UID<          nobody
UID>             systemd-network
<UID<          dbus
UID>             polkitd
<UID<          sshd
<UID<          postfix
UID>             ajie
UID>             chrony
UID>             deploy
UID>             nginx
[root@localhost shell]# 

循环语句-do while

do while
do
    动作
while(条件表达式)

循环语句-for

for
for(初始化计数器;测试计数器;计数器变更)
    动作

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

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

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

[root@localhost shell]# cat student.txt
Name    chinese    english    math    physical    average
Allen
Mike
Zhang
Jerry
Han
Li                

# 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
Mike
Zhang
Jerry
Han
Li
[root@localhost shell]# cat student.awk
BEGIN{
    printf "%-10s%-10s%-10s%-10s%-10s%-10s\n","Name","Chinese","English","Math","Physical","Average"
}

{
    total=$+$+$+$
    avg=total/
    if(avg>)
    {
        printf "%-10s%-10d%-10d%-10d%-10d%-0.2f\n",$,$,$,$,$,avg
        # 将每一科的成绩累加起来保存在一个变量中
        score_chinese+=$
        score_english+=$
        score_math+=$
        score_physical=$
    }
}
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                                     91.00
Mike                                      93.50
Li                                       91.00
Name