printf 命令

我就是我 2022-07-14 08:25 219阅读 0赞

printf 命令模仿 C 程序库（library）里的 printf() 程序。标准定义，因此使用printf的脚本比使用echo移植性好。printf 使用引用文本或空格分隔的参数，外面可以在printf中使用格式化字符串，还可以制定字符串的宽度、左右对齐方式等。默认printf不会像 echo 自动添加换行符，我们可以手动添加 \\n。

printf 命令的语法：

printf  format-string  \[arguments...\]

参数说明：

format-string: 为格式控制字符串

arguments: 为参数列表。

[root@localhost tsh]# vim test.sh
    #!/bin/bash
    echo "Hello, Shell"
    printf "Hello, Shell\n"
    echo hello
    
    [root@localhost tsh]# chmod +x test.sh
    [root@localhost tsh]# ./test.sh 
    Hello, Shell
    Hello, Shell
    hello

例：

[root@localhost tsh]# vim test.sh
    #!/bin/bash
    printf "%-10s %-8s %-4s\n" 姓名 性别 体重kg  
    printf "%-10s %-8s %-4.2f\n" 郭靖 男 66.1234 
    printf "%-10s %-8s %-4.2f\n" 杨过 男 48.6543 
    printf "%-10s %-8s %-4.2f\n" 郭芙 女 47.9876 
    
    [root@localhost tsh]# chmod +x test.sh
    [root@localhost tsh]# ./test.sh 
    姓名 性别 体重kg
    郭靖 男 66.12
    杨过 男 48.65
    郭芙 女 47.99

%s %c %d %f都是格式替代符

%-10s 指一个宽度为10个字符（-表示左对齐，没有则表示右对齐），任何字符都会被显示在10个字符宽的字符内，如果不足则自动以空格填充，超过也会将内容全部显示出来。

%-4.2f 指格式化为小数，其中.2指保留2位小数。

例：

[root@localhost tsh]# vim test.sh
    #!/bin/bash
    # format-string为双引号
    printf "%d %s\n" 1 "abc"
    # 单引号与双引号效果一样 
    printf '%d %s\n' 1 "abc" 
    # 没有引号也可以输出
    printf %s abcdef
    # 格式只指定了一个参数，但多出的参数仍然会按照该格式输出，format-string 被重用
    printf %s abc def
    printf "%s\n" abc def
    printf "%s %s %s\n" a b c d e f g h i j
    # 如果没有 arguments，那么 %s 用NULL代替，%d 用 0 代替
    printf "%s and %d \n" 
    
    [root@localhost tsh]# chmod +x test.sh
    [root@localhost tsh]# ./test.sh 
    1 abc
    1 abc
    abcdefabcdefabc
    def
    a b c
    d e f
    g h i
    j 
    and 0

printf的转义序列

<table style="font-size:undefined; border-collapse:collapse; margin-top:10px; margin-bottom:10px; table-layout:fixed; border:1px solid rgb(204,204,204); width:596px; background-color:inherit"> 
 <tbody style="background-color:inherit"> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> 序列</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 说明</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \a</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 警告字符，通常为ASCII的BEL字符</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \b</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 后退</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \c</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 抑制（不显示）输出结果中任何结尾的换行字符（只在%b格式指示符控制下的参数字符串中有效），而且，任何留在参数里的字符、任何接下来的参数以及任何留在格式字符串中的字符，都被忽略</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \f</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 换页（formfeed）</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \n</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 换行</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \r</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 回车（Carriage return）</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \t</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 水平制表符</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \v</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 垂直制表符</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \\</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 一个字面上的反斜杠字符</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \ddd</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 表示1到3位数八进制值的字符。仅在格式字符串中有效</td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:81px; vertical-align:middle; background-color:inherit"> \0ddd</td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 16px 5px 12px; min-height:25px; min-width:25px; height:32px; word-wrap:break-word; width:515px; vertical-align:middle; background-color:inherit"> 表示1到3位的八进制值字符</td> 
  </tr> 
 </tbody> 
</table>

例：

[root@localhost tsh]# vim test.sh
    #!/bin/bash
    printf "beijing:<%s>\n" "A\nB"
    printf "shanghai:<%b>\n" "A\nB"
    printf "hangzhou \a"
    
    [root@localhost tsh]# chmod +x test.sh
    [root@localhost tsh]# ./test.sh 
    beijing:
    shanghai:B>
    hangzhou