问题描述
我正在尝试在终端上运行一个for循环，在该终端上，我想将每个迭代发送到后台进程，以使它们全部同时运行.
I am trying to run a for loop on the terminal where I want to send each iteration to background process so that all of them run simultaneously.
以下是命令逐一运行
for i in *.sra; do fastq-dump --split-files $i ; done # ";" only
我突出显示了分号.
要同时运行，这行得通
for i in *.sra; do fastq-dump --split-files $i & done # "&" only
但这会导致错误
for i in *.sra; do fastq-dump --split-files $i & ; done # "& ;"
如果有人解释这里发生的事情，那就太好了.我知道这应该以适当的缩进方式以Shell脚本的方式编写，但是有时候我只能运行此命令.
It would be nice if some one explains what is going on here. I know this should be written in a shell script way with proper indentation, but some times I only have this command to run.
推荐答案
&和;都终止它们之前的命令.
& and ; both terminate the command that precedes them.
写& ;的内容不能超过写; ;或& &的内容，因为该语言只允许命令终止一次(并且不允许将零字列表作为命令) ).
You can't write & ; any more than you could write ; ; or & &, because the language only allows a command to be terminated once (and doesn't permit a zero-word list as a command).
因此:for i in *.src; do fastq-dump --split-files "$i" & done完全是正确的，不需要额外的;.
Thus: for i in *.src; do fastq-dump --split-files "$i" & done is perfectly correct as-is, and does not require an additional ;.
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