Linux shell fold命令用于限制文件列宽。

fold 命令会从指定的文件里读取内容，将超过限定列宽的列加入增列字符后，输出到标准输出设备。

若不指定任何文件名称，或是所给予的文件名为 -，则 fold 命令会从标准输入设备读取数据。

fold 命令语法格式

fold [-bs][-w][--help][--version][文件...]

参数

-b , --bytes

以Byte为单位计算列宽，而非采用行数编号为单位。

-s , --spaces

以空格字符作为换列点

-w , --width

设置每列的最大行数

--help

在线帮助

--version

显示版本信息

范例

假设存在 demo6.txt 文件，内容如下

[root@localhost ~/shell]# cat demo6.txt

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 以每行宽度 30 字符折行

[root@localhost ~/shell]# fold -w 30 demo6.txt

Linux networks are becoming mo

re and more common, but

security is often an overlooke

d

issue. Unfortunately, in today

’s environment all networks

are potential hacker targets,

from top-secret military resea

rch networks to small home LAN

s.

Linux Network Security focuses

on securing Linux in a

networked environment, where t

he

security of the entire network

needs to be considered

rather than just isolated mach

ines.

It uses a mix of theory and pr

actical techniques to

teach administrators how to in

stall and

use security applications, as

well as how the

applications work and why they

are necessary.