bash 从两个不同脚本的 fifo 写入和读取
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Write and read from a fifo from two different script
提问by Ciccio
I have two bash script. One script write in a fifo. The second one read from the fifo, but AFTER the first one end to write.
我有两个 bash 脚本。一个脚本写在一个先进先出。第二个从fifo读取，但在第一个结束后写入。
But something does not work. I do not understand where the problem is. Here the code.
但是有些东西不起作用。我不明白问题出在哪里。这里是代码。
The first script is (the writer):
第一个脚本是（作者）：
#!/bin/bash
fifo_name="myfifo";
# Se non esiste, crea la fifo;
[ -p $fifo_name ] || mkfifo $fifo_name;
exec 3<> $fifo_name;
echo "foo" > $fifo_name;
echo "bar" > $fifo_name;
The second script is (the reader):
第二个脚本是（读者）：
#!/bin/bash
fifo_name="myfifo";
while true
do
if read line <$fifo_name; then
# if [[ "$line" == 'ar' ]]; then
# break
#fi
echo $line
fi
done
Can anyone help me please? Thank you
有人可以帮我吗？谢谢
采纳答案by John1024
Replace the second script with:
将第二个脚本替换为：
#!/bin/bash
fifo_name="myfifo"
while true
do
if read line; then
echo $line
fi
done <"$fifo_name"
This opens the fifo only once and reads every line from it.
这只会打开 fifo 一次并从中读取每一行。
回答by David C. Rankin
The problem with your setup is that you have fifo creation in the wrong script if you wish to control fifo access to time when the reader is actually running. In order to correct the problem you will need to do something like this:
您设置的问题在于，如果您希望在阅读器实际运行时控制 fifo 访问时间，则您在错误的脚本中创建了 fifo。为了更正问题，您需要执行以下操作：
reader: fifo_read.sh
阅读器：fifo_read.sh
#!/bin/bash
fifo_name="/tmp/myfifo" # fifo name
trap "rm -f $fifo_name" EXIT # set trap to rm fifo_name at exit
[ -p "$fifo_name" ] || mkfifo "$fifo_name" # if fifo not found, create
exec 3< $fifo_name # redirect fifo_name to fd 3
# (not required, but makes read clearer)
while :; do
if read -r -u 3 line; then # read line from fifo_name
if [ "$line" = 'quit' ]; then # if line is quit, quit
printf "%s: 'quit' command received\n" "$fifo_name"
break
fi
printf "%s: %s\n" "$fifo_name" "$line" # print line read
fi
done
exec 3<&- # reset fd 3 redirection
exit 0
writer: fifo_write.sh
作者：fifo_write.sh
#!/bin/bash
fifo_name="/tmp/myfifo"
# Se non esiste, exit :);
[ -p "$fifo_name" ] || {
printf "\n Error fifo '%s' not found.\n\n" "$fifo_name"
exit 1
}
[ -n "" ] &&
printf "%s\n" "" > "$fifo_name" ||
printf "pid: '%s' writing to fifo\n" "$$" > "$fifo_name"
exit 0
operation: (start reader in 1st terminal)
操作：（在第一个终端启动阅读器）
$ ./fifo_read.sh # you can background with & at end
(launch writer in second terminal)
（在第二个终端启动 writer）
$ ./fifo_write.sh "message from writer" # second terminal
$ ./fifo_write.sh
$ ./fifo_write.sh quit
output in 1st terminal:
第一个终端的输出：
$ ./fifo_read.sh
/tmp/myfifo: message from writer
/tmp/myfifo: pid: '28698' writing to fifo
/tmp/myfifo: 'quit' command received
回答by Julian
The following script should do the job:
以下脚本应该可以完成这项工作：
#!/bin/bash
FIFO="/tmp/fifo"
if [ ! -e "$FIFO" ]; then
mkfifo "$FIFO"
fi
for script in "$@"; do
echo $script > $FIFO &
done
while read script; do
/bin/bash -c $script
done < $FIFO
Given two script a.sh and b.sh where both scripts pass "a" and "b" to stdout, respectively, one will get the following result (given that the script above is called test.sh):
给定两个脚本 a.sh 和 b.sh，其中两个脚本分别将“a”和“b”传递给 stdout，将得到以下结果（假设上面的脚本称为 test.sh）：
./test.sh /tmp/a.sh /tmp/b.sh
a
b
Best, Julian
最好的，朱利安
