在 bash 中读取多行而不产生新的子shell？
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Reading multiple lines in bash without spawning a new subshell?
提问by swampsjohn
I'm trying to do something like
我正在尝试做类似的事情
var=0
grep "foo" bar | while read line; do
var=1
done
Unfortunately this doesn't work since the pipe causes the while to run in a subshell. Is there a better way to do this? I don't need to use "read" if there's another solution.
不幸的是，这不起作用，因为管道导致 while 在子shell中运行。有一个更好的方法吗？如果有其他解决方案，我不需要使用“阅读”。
I've looked at Bash variable scopewhich is similar, but I couldn't get anything that worked from it.
我看过类似的Bash 变量范围，但我无法从中得到任何有用的东西。
回答by Kaleb Pederson
If you really are doing something that simplistic, you don't even need the while readloop. The following would work:
如果你真的在做一些简单的事情，你甚至不需要while read循环。以下将起作用：
VAR=0
grep "foo" bar && VAR=1
# ...
If you really do need the loop, because other things are happening in the loop, you can redirect from a <( commands )process substitution:
如果您确实需要循环，因为循环中正在发生其他事情，您可以从<( commands )进程替换重定向：
VAR=0
while read line ; do
VAR=1
# do other stuff
done < <(grep "foo" bar)
回答by ghostdog74
then don't use pipe ,and lose the grep
然后不要使用管道，并失去 grep
var=1
while read line
do
case "$line" in
*foo* ) var=1
esac
done <"file"
echo "var after: $var"
