linux - 尝试在没有阅读器的情况下写时捕获SIGPIPE

我试图在bash中实现两个进程之间的命名管道通信解决方案。
第一个进程向命名管道写入内容：

send(){
    echo 'something' > $NAMEDPIPE
}

第二个脚本应该像这样读取命名管道：

while true;do
  if read line < $NAMEDPIPE;do
      someCommands
  fi
done

注意，命名管道以前是使用传统命令创建的

mkfifo $NAMEDPIPE

我的问题是，读写器脚本并不总是在运行，因此，如果读写器脚本尝试写入命名管道，它将一直处于阻塞状态，直到读写器连接到管道。
我想避免这种行为，一个解决方案是捕获sigpipe信号。事实上，根据man 7的说法，当试图在没有读卡器的管道中写作时，信号应该被发送。所以我改变了我的红色功能：

read(){
    trap 'echo "SIGPIPE received"' SIGPIPE
    echo 'something' > $NAMEDPIPE
}

但当我运行reader脚本时，脚本将保持阻塞状态，并且不会打印“sigpipe received”。
我是误会了信号机制，还是有更好的办法来解决我的问题？

最佳答案

这是我刚做的一个有趣的代码。或许你可以这样说：

#!/bin/bash

shopt -s extglob

NAMEDPIPE=/var/run/sr-pipe
RECEIVER_PID_FILE=/var/run/sr-receiver-pid

function sender_start {
    # Create named pipe.

    if [[ -e $NAMEDPIPE ]]; then
        echo "[Sender] Named pipe \"$NAMEDPIPE\" already exists."
    else
        echo "[Sender] Creating named pipe \"$NAMEDPIPE\"."
        mkfifo "$NAMEDPIPE" || {
            echo "Failed to create named pipe \"$NAMEDPIPE\"."
            exit 1
        }
    fi

    # Wait for receiver.

    echo "[Sender] Waiting for receiver."
    local PID
    until [[ -e $RECEIVER_PID_FILE ]] \
    && read PID < "$RECEIVER_PID_FILE" \
    && [[ $PID == +([[:digit:]]) ]] \
    && kill -s 0 "$PID" &>/dev/null; do
        sleep 1s
    done
    echo "[Sender] Receiver is [now] active."

    # Send signal.

    kill -s SIGPIPE "$PID"

    # Send messages.

    local SEND=''

    echo "[Sender] Now sending messages."
    while sleep 1s; do
        SEND=$RANDOM
        echo "[Sender] Sending $SEND."
        echo "$SEND" >&4
    done 4>"$NAMEDPIPE"
}

function receiver_start {
    echo "$BASHPID" > "$RECEIVER_PID_FILE"

    echo "[Receiver] Receiver is now active."

    local QUIT=false RECEIVE=false

    trap 'RECEIVE=true' SIGPIPE
    trap 'QUIT=true' SIGINT SIGTERM SIGHUP

    while [[ $QUIT == false ]]; do
        if [[ $RECEIVE == true ]]; then
            RECEIVE=false
            echo "[Receiver] Now receiving messages."
            while [[ $QUIT == false ]] && IFS= read -r -u 4 LINE; do
                echo "[Receiver] Received $LINE."
            done 4<"$NAMEDPIPE"
        fi
        sleep 1s
    done
}

if [[ $1 == send ]]; then
    sender_start
elif [[ $1 == receive ]]; then
    receiver_start
fi

在一个终端上我运行了这个：

# bash sender-receiver.sh send
[Sender] Named pipe "/var/run/sr-pipe" already exists.
[Sender] Waiting for receiver.
[Sender] Receiver is [now] active.
[Sender] Now sending messages.
[Sender] Sending 21524.
[Sender] Sending 1460.
[Sender] Sending 8352.
[Sender] Sending 4424.
...

另一方面，我得到了这个（修正）：

# bash sender-receiver.sh receive
[Receiver] Receiver is now active.
[Receiver] Now receiving messages.
[Receiver] Received 21524.
[Receiver] Received 1460.
[Receiver] Received 8352.
[Receiver] Received 4424.
...

你可以在后台运行sender，在前台运行receiver。

关于linux - 尝试在没有阅读器的情况下写时捕获SIGPIPE，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/24201856/