Linux fold Command

Linux Command Encyclopedia

The Linux fold command is used to limit file column width.

The fold command reads content from the specified file, adds wrap characters to columns exceeding the limited column width, and outputs to the standard output device. If no file name is given, or if the given file name is "-", the fold command reads data from standard input.

Syntax

fold [-bs][-w<每列行数>][--help][--version][文件...]

Parameters：

• -b or --bytes Calculates column width in bytes, rather than using line count as the unit.
• -s or --spaces Uses space characters as column break points.
• -w<number of characters per line> or --width<number of characters per line> Sets the maximum line width.
• --help Online help.
• --version Displays version information.

Examples

To fold the lines of a file named testfile to a width of 30, you can use the following command:

fold -w 30 testfile

For comparison, first output the testfile file as follows:

$ cat testfile #查看testfile 中的内容  
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. 

Then use the fold command to fold and display it:

$ fold -w 30 testfile #行折叠成宽度为30，显示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 

Linux Command Encyclopedia