Linux Bash 参数的最大数量！= max num cp 参数？
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Maximum number of Bash arguments != max num cp arguments?
提问by Lee Netherton
I have recently been copying and moving a large number of files (~400,000). I know that there are limitations on the number of arguments that can be expanded on the Bash command line, so I have been using xargs to limit the numbers produced.
我最近一直在复制和移动大量文件（~400,000）。我知道可以在 Bash 命令行上扩展的参数数量有限制，所以我一直使用 xargs 来限制产生的数量。
Out of curiosity, I wondered what the maximum number of arguments that I could use was, and I found this postsaying that it was system-dependant, and that I could run this command to find out:
出于好奇，我想知道我可以使用的最大参数数量是多少，我发现这篇文章说它依赖于系统，我可以运行这个命令来找出：
$ getconf ARG_MAX
To my surprise, the anwser I got back was:
令我惊讶的是，我得到的答案是：
2621440
Just over 2.6 million. As I said, the number of files that I am manipulating is much less than this -- around 400k. I definitely need to use the xargsmethod of moving and copying these files, because I tried using a normal mv * ...or cp * ...and got a 'Argument list too long' error.
刚刚超过260万。正如我所说，我正在处理的文件数量远少于此 - 大约 400k。我肯定需要使用xargs移动和复制这些文件的方法，因为我尝试使用普通mv * ...或cp * ...并得到“参数列表太长”错误。
So, do the mvand cpcommands have their own fixed limit on the number of arguments that I can use (I couldn't find anything in their man pages), or am I missing something?
那么，mvandcp命令对我可以使用的参数数量是否有自己的固定限制（我在他们的手册页中找不到任何内容），还是我遗漏了什么？
采纳答案by Wyatt Anderson
As Ignacio said, ARG_MAXis the maximum length of the bufferof arguments passed to exec(), not the maximum number of files (this pagehas a very in-depth explanation). Specifically, it lists fs/exec.cas checking the following condition:
正如 Ignacio 所说，ARG_MAX是传递给 的参数缓冲区的最大长度exec()，而不是最大文件数（此页面有非常深入的解释）。具体来说，它列出fs/exec.c了检查以下条件：
PAGE_SIZE*MAX_ARG_PAGES-sizeof(void *) / sizeof(void *)
And, it seems, you have some additional limitations:
而且，您似乎还有一些额外的限制：
On a 32-bit Linux, this is ARGMAX/4-1 (32767). This becomes relevant if the average length of arguments is smaller than 4. Since Linux 2.6.23, this function tests if the number exceeds
MAX_ARG_STRINGSin<linux/binfmts.h>(2^32-1 = 4294967296-1). And as additional limit, one argument must not be longer thanMAX_ARG_STRLEN(131072).
在 32 位 Linux 上，这是ARGMAX/4-1 (32767)。这将成为相关如果参数的平均长度小于4.由于Linux 2.6.23，该功能检查，如果数量超过
MAX_ARG_STRINGS在<linux/binfmts.h>（2 ^ 32-1 = 4294967296-1）。作为附加限制，一个参数不得长于MAX_ARG_STRLEN(131072)。
回答by Ignacio Vazquez-Abrams
ARG_MAXis the maximum length of the arguments to the exec(3)functions. A shell is not required to support passing this length of arguments from its command line.
ARG_MAX是exec(3)函数参数的最大长度。shell 不需要支持从它的命令行传递这个长度的参数。
