Linux fold命令

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Linux fold命令用于限制文件列寬。

fold指令會(huì)從指定的文件里讀取內(nèi)容，將超過限定列寬的列加入增列字符后，輸出到標(biāo)準(zhǔn)輸出設(shè)備。若不指定任何文件名稱，或是所給予的文件名為"-"，則fold指令會(huì)從標(biāo)準(zhǔn)輸入設(shè)備讀取數(shù)據(jù)。

語法

fold [-bs][-w<每列行數(shù)>][--help][--version][文件...]

參數(shù)：

  • -b或--bytes 以Byte為單位計(jì)算列寬，而非采用行數(shù)編號(hào)為單位。
  • -s或--spaces 以空格字符作為換列點(diǎn)。
  • -w<每列行數(shù)>或--width<每列行數(shù)> 設(shè)置每列的最大行數(shù)。
  • --help 在線幫助。
  • --version 顯示版本信息。

實(shí)例

將一個(gè)名為testfile 的文件的行折疊成寬度為30，可使用如下命令： 

fold -w 30 testfile

為了對(duì)比，先將testfile文件輸出如下：

$ cat testfile #查看testfile 中的內(nèi)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.

然后使用fold命令折疊顯示：

$ fold -w 30 testfile #行折疊成寬度為30，顯示testfile 文件  
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

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