bash xargs -l 的替代方案

Alternatives to xargs -l

提问by eatloaf

I want to rename a bunch of dirs from DIR to DIR.OLD. Ideally I would use the following:

我想将一堆目录从 DIR 重命名为 DIR.OLD。理想情况下，我会使用以下内容：

find . -maxdepth 1 -type d -name \"*.y\" -mtime +`expr 2 \* 365` -print0 | xargs -0 -r -I file mv file file.old

But the machine I want to execute this on has BusyBox installed and the BusyBox xargs doesn't support the "-I" option.

但是我想在其上执行此操作的机器安装了 BusyBox 并且 BusyBox xargs 不支持“-I”选项。

What are some common alternative methods for collecting an array of files and then executing on them in a shell script?

收集文件数组然后在 shell 脚本中对它们执行的一些常见替代方法是什么？

回答by praetorian droid

You can use -execand {}features of the findcommand so you don't need any pipes at all:

您可以使用命令的-exec和{}功能，find因此根本不需要任何管道：

find -maxdepth 1 -type d -name "*.y" -mtime +`expr 2 \* 365` -exec mv "{}" "{}.old" \;

Also you don't need to specify '.' path - this is default for find. And you used extra slashes in "*.y". Of course if your file names do not really contain quotes.

你也不需要指定 '.' 路径 - 这是find. 并且您在"*.y". 当然，如果您的文件名实际上不包含引号。

In fairness it should be noted, that version with while readloop is the fastest of proposed here. Here are some example measurements:

公平地说，应该注意的是，带有while read循环的版本是这里提出的最快的版本。以下是一些示例测量：

$ cat measure 
#!/bin/sh
case  in
  1) find "" -print0 | xargs -0 -I file echo mv file file.old ;;

  2) find "" -exec echo mv '{}' '{}.old' \; ;;

  3) find "" | while read file; do
       echo mv "$file" "$file.old"
     done;;
esac
$ time ./measure android-ndk-r5c 1 | wc
   6225   18675  955493
real    0m6.585s
user    0m18.933s
sys     0m4.476s
$ time ./measure android-ndk-r5c 2 | wc
   6225   18675  955493
real    0m6.877s
user    0m18.517s
sys     0m4.788s
$ time ./measure android-ndk-r5c 3 | wc
   6225   18675  955493
real    0m0.262s
user    0m0.088s
sys     0m0.236s

I think it's because findand xargsinvokes additional /bin/sh (actually exec(3)does it) every time for execute a command, while shell whileloop do not.

我想这是因为find与xargs所调用额外的/ bin / sh的（实际上exec(3)确实是）为执行命令每一次，而壳while循环不。

Upd:If your busybox version was compiled without -execoption support for the findcommand then the whileloop or xargs, suggested in the other answers (one, two), is your way.

更新：如果您的 busybox 版本是在没有-exec选项支持find命令的情况下编译的，那么在其他答案（一、二）中建议的while循环或就是您的方式。xargs

回答by Jan Hudec

1. Use a forloop. Unfortunately I don't think busybox understands read -0either, so you won't be able to handle newlines properly. If you don't need to, it's easiest to just:

   find . -maxdepth 1 -type d -name \"*.y\" -mtime +`expr 2 \* 365` -print | while read file; do mv -- "$file" "$file".old; done
   

2. Use a sh -cas the command. Note the slightly weird use of $0to name the first argument (it would normally be the script name and that goes to $0and while you are suppressing script with -c, the argument still goes to $0) and the use of -n 1to avoid batching.

   find . -maxdepth 1 -type d -name \"*.y\" -mtime +`expr 2 \* 365` -print0 | xargs -0 -r -n 1 sh -c 'mv -- "
   find . -maxdepth 1 -type d -name \"*.y\" -mtime +`expr 2 \* 365` -print | while read file; do mv -- "$file" "$file".old; done
   " "
   find . -maxdepth 1 -type d -name \"*.y\" -mtime +`expr 2 \* 365` -print0 | xargs -0 -r -n 1 sh -c 'mv -- "
   find . -maxdepth 1 -type d -name \"*.y\" -mtime +`expr 2 \* 365` -print | while IFS= read file
   do
       mv "$file" "$file".old
   done
   " "##代码##".old'
   ".old'
   

1. 使用for循环。不幸的是，我认为busybox 也不理解read -0，因此您将无法正确处理换行符。如果您不需要，最简单的方法是：

   ##代码##

2. 使用 ash -c作为命令。请注意$0命名第一个参数的稍微奇怪的用法（它通常是脚本名称，$0并且当您使用 抑制脚本时-c，参数仍然转到$0）以及使用-n 1避免批处理。

   ##代码##

EditOops: I forgot about the find -execagain.

编辑糟糕：我又忘记find -exec了。

回答by dogbane

An alternative is to use a loop:

另一种方法是使用循环：

##代码##