linux的fold命令

如果需要对fasta文件截取长度，比如每行碱基个数为100或者为60，还记得硕士期间处理它的方法是用了一个排列软件，现在只需要用一个linux命令即可。看下面这个简单的例子，就能立刻明白fold的用途。
学习链接：https://www.gnu.org/software/coreutils/manual/html_node/index.html#SEC_Contents

$ fold --help
Usage: fold [OPTION]... [FILE]...
Wrap input lines in each FILE, writing to standard output.

With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
  -b, --bytes         count bytes rather than columns
  -s, --spaces        break at spaces
  -w, --width=WIDTH   use WIDTH columns instead of 80
      --help     display this help and exit
      --version  output version information and exit

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Full documentation at: <http://www.gnu.org/software/coreutils/fold>
or available locally via: info '(coreutils) fold invocation'

$ fold --version 
fold (GNU coreutils) 8.25
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by David MacKenzie.

选项列表

选项	说明
--help	显示帮助文档
--version	显示版本信息
-b | --bytes	以字节为单位，指定宽度
-c | --characters	以字符为单位，指定宽度
-s | --space	以空格分割
-w | --width	指定列宽，默认80

示例

$ echo ATGCGCGCGC|fold -w 3
ATG
CGC
GCG
C
$ echo ATGCGCGCGC|fold -w 3|tee new.fa
# 宽度，默认80

$ cat fa1|fold -b3
ATG
CGC
GCG
C
# 字节个数