shell编程连载【1】-创建归档文件

(1) vi bundle.sh

#! /bin/bash #bundle :group files into distribution package echo "# To unbundle, bash this file" for i do echo "echo $i 1>&2" echo "cat >$i <<'End of $i'" cat $i echo "End of $i" done

(2)

cat h1.txt

hello1

hello2

cat h2.txt hello3

(3) 执行sh boudle.sh h1.txt h2.txt >bakfiles

(4)

rm h1.txt h2.txt

(5) 执行bash bakfiles可恢复h1.txt，h2.txt

【解析】

(1)为什么执行bash bakfiles可恢复h1.txt，h2.txt?

先来看一下bakfiles的内容，执行cat bakfiles

# To unbundle, bash this file
echo h1.txt 1>&2
cat >h1.txt <<'End of h1.txt'
hello1
hello2

End of h1.txt
echo h2.txt 1>&2
cat >h2.txt <<'End of h2.txt'
hello3
End of h2.txt
原来在执行sh boudle.sh h1.txt h2.txt >bakfiles后，bakfiles中生成了2条文件重定向语句：

cat >h1.txt <<'End of h1.txt'
cat >h2.txt <<'End of h2.txt'
再用bash解析bakfiles也就达到了恢复文件的目的。

(2) 1>&2的涵义

0：标准输入

1：标准输出

2：标准错误

>&：可复制的文件描述符

1>&2即是将标准输出重定向为标准错误。