>和>&有什么区别？

xmin · 发表于 2006-1-6 16:56:09

例如：
cat < readme > towrite
cat < readme >& towrite

二者功能上一样，执行过程上有区别么？

yongjian · 发表于 2006-1-6 22:44:43

[CODE]>&/<& means duplicate output/input not just redirect. But if towrite is not linked with file descriptor, then its probably just like the >file...

寂寞烈火 · 发表于 2006-1-7 00:25:15

它们一样吗?

> filename
# The > truncates file "filename" to zero length.
# If file not present, creates zero−length file (same effect as 'touch').
# (Same result as ": >", above, but this does not work with some shells.)

>&j
# Redirects, by default, file descriptor 1 (stdout) to j.
# All stdout gets sent to file pointed to by j.

yongjian · 发表于 2006-1-8 13:10:58

Post by 寂寞烈火
它们一样吗?

Well, only if >&n when n is a file descriptor. If n is just a regular file, I really don't see any difference.

cat "abcd" >bb = cat "abcd" >&bb

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when bb is a regular file. But

cat "abcd">3 != (exec 3>bb && cat "abcd" >&3)

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since the first 3 is a regular file and the second is a file descriptor...

寂寞烈火 · 发表于 2006-1-8 17:04:32

Post by yongjian
Well, only if >&n when n is a file descriptor. If n is just a regular file, I really don't see any difference.
cat "abcd" >bb = cat "abcd" >&bb
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when bb is a regular file. But
cat "abcd">3 != (exec 3>bb && cat "abcd" >&3)
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since the first 3 is a regular file and the second is a file descriptor...

chenxingchen · 发表于 2006-1-15 14:47:00

《Unix Shell编程》中说>& ，连接两个文件描述符使他们能指向同一个文件

yongjian · 发表于 2006-1-16 09:54:25

Yes, regarding to file descriptor, the second one will be a copy of the original one. Look at

ls -la /dev/fd/

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jiazhengw · 发表于 2006-1-17 20:32:13

＞file,重定向到一个文件；
＞＆n,重定向到文件描述符。

appless · 发表于 2006-1-19 14:24:08

Post by jiazhengw

＞＆n,重定向到文件描述符。

啥叫文件描述符????

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&gt;和&gt;&amp;有什么区别？

>和>&有什么区别？