bash 计算“查找”结果的最佳方法是什么？
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What is the best way to count "find" results?
提问by MechMK1
My current solution would be find <expr> -exec printf '.' \; | wc -c, but this takes far too long when there are more than 10000 results. Is there no faster/better way to do this?
我目前的解决方案是find <expr> -exec printf '.' \; | wc -c，但是当结果超过 10000 时，这需要很长时间。有没有更快/更好的方法来做到这一点？
采纳答案by Gilles Quenot
Try this instead (require find's -printfsupport):
试试这个（需要find的-printf支持）：
find <expr> -type f -printf '.' | wc -c
It will be more reliable and faster than counting the lines.
它将比计算线路更可靠、更快。
Note that I use the find's printf, not an external command.
请注意，我使用的是find's printf，而不是外部命令。
Let's bench a bit :
让我们稍作休息：
$ ls -1
a
e
l
ll.sh
r
t
y
z
My snippet benchmark :
我的片段基准：
$ time find -type f -printf '.' | wc -c
8
real 0m0.004s
user 0m0.000s
sys 0m0.007s
With full lines :
全线：
$ time find -type f | wc -l
8
real 0m0.006s
user 0m0.003s
sys 0m0.000s
So my solution is faster =) (the important part is the realline)
所以我的解决方案更快=）（重要的部分是real线路）
回答by Brian Agnew
Why not
为什么不
find <expr> | wc -l
as a simple portable solution ? Your original solution is spawning a new processprintffor every individual file found, and that's very expensive (as you've just found).
作为一个简单的便携式解决方案？您最初的解决方案是为找到的每个单独文件生成一个新进程printf，这非常昂贵（正如您刚刚发现的那样）。
Note that this will overcount if you have filenames with newlines embedded, but if you have that then I suspect your problems run a little deeper :-)
请注意，如果您有嵌入换行符的文件名，这将多计，但如果您有，那么我怀疑您的问题会更深一些:-)
回答by John B
This solution is certainly slower than some of the other find -> wcsolutions here, but if you were inclined to do something else with the file names in addition to counting them, you could readfrom the findoutput.
这个解决方案肯定比find -> wc这里的其他一些解决方案慢，但是如果除了计算文件名之外，您还倾向于对文件名做其他事情，您可以read从find输出中获取。
n=0
while read -r -d ''; do
((n++)) # count
# maybe perform another act on file
done < <(find <expr> -print0)
echo $n
It is just a modification of a solutionfound in BashGuide that properly handles files with nonstandard names by making the findoutput delimiter a NUL byte using print0, and reading from it using ''(NUL byte) as the loop delimiter.
它只是对 BashGuide 中找到的解决方案的修改，该解决方案通过使用 将find输出定界符设为NUL 字节print0，并使用''(NUL 字节) 作为循环定界符从中读取来正确处理具有非标准名称的文件。
回答by carlo
This is my countfilesfunction in my ~/.bashrc(it's reasonably fast, should work for Linux & FreeBSD find, and does not get fooled by file paths containing newline characters; the final wcjust counts NUL bytes):
这是我的countfiles函数~/.bashrc（它相当快，应该适用于 Linux 和 FreeBSD find，并且不会被包含换行符的文件路径所迷惑；最后wc只计算 NUL 字节）：
countfiles ()
{
command find "${1:-.}" -type f -name "${2:-*}" -print0 |
command tr -dc '##代码##' | command wc -c;
return 0
}
countfiles
countfiles ~ '*.txt'
