Linux fold命令

Linux 中的 fold 命令用于限制文件内容的列宽。

fold 命令会从指定的文件中读取内容，当某行内容超过设定的列宽时，会插入额外的字符进行换行处理，并将结果输出到标准输出。如果不指定文件名，或者提供的文件名为“-”，则 fold 会从标准输入读取数据。

语法

<code>fold [-bs][-w][--help][--version][文件...]</code>

参数说明：

• -b 或 --bytes：以字节为单位计算列宽。
• -s 或 --spaces：以空格作为换行的分割点。
• -w 或 --width：设置每列的最大宽度。
• --help：查看在线帮助文档。
• --version：显示程序版本信息。

示例

假设有一个名为 testfile 的文件，现在要将其内容按照每行30个字符的宽度进行折叠显示，可以执行以下命令：

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<code>fold -w 30 testfile</code>

在操作之前，先查看一下 testfile 文件的内容：

<code>$ cat testfile # 查看testfile 文件内容  
Linux networks are becoming more and more common, but 
security is often an overlooked  
issue. Unfortunately, in today’s environment all networks 
are potential hacker targets,  
from top-secret military research networks to small home LANs.  
Linux Network Security focuses on securing Linux in a 
networked environment, where the  
security of the entire network needs to be considered 
rather than just isolated machines.  
It uses a mix of theory and practical techniques to 
teach administrators how to install and  
use security applications, as well as how the 
applications work and why they are necessary. </code>

接下来使用 fold 命令进行格式化输出：

<code>$ fold -w 30 testfile # 将testfile 文件按30字符宽度换行显示  
Linux networks are becoming mo  
re and more common, but securi  
ty is often an overlooked issu  
e. Unfortunately, in today’s  
environment all networks are  
potential hacker targets, from  
top-secret military research  
networks to small home LANs.  
Linux Network Security focuses  
on securing Linux in a networ  
ked environment, where the sec  
urity of the entire network ne  
eds to be considered rather th  
an just isolated machines. It  
uses a mix of theory and pract  
ical techniques to teach admin  
istrators how to install and u  
se security applications, as w  
ell as how the applications wo  
rk and why they are necessary </code>