Linux fold command

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The Linux fold command is used to limit the column width of files.

The fold command reads content from the specified file, adds an increment character to columns exceeding the specified column width, and outputs it to the standard output device. If no file name is specified, or the given file name is-If so, the fold command will read data from the standard input device.

Syntax

fold　[-bs][-w<column lines>][--help][--version][file...]

parameters:

• -b or--bytes Calculate column width in bytes, not in line number units.

• -s or--spaces Use space characters as the column break.

• -w<number of lines per column> or--width<number of lines per column> Set the maximum number of lines per column.

• --help Online help.

• --version Show version information.

Online example

Fold the lines of a file named testfile to a width of30, you can use the following command:

fold　-w　30 testfile

For comparison, first output the testfile file as follows:

$ cat testfile # View the content of testfile　　
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-from secret military research networks to small home LANs.　　
Linux Network Security focuses on securing Linux in a　
networked environment, where the　　
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:

$ fold　-w　30 testfile # Line folding to width of30, display testfile file　　
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 from 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　　
administrators 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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