Why my named pipe input command line just hangs when it is called?

问题

Why my named pipe input command line just hangs when it is called?

Based on the answers:

1. Writing to stdin of background process
2. Accessing bash command line args $@ vs $*
3. Send command to a background process
4. Can I redirect output to a log file and background a process at the same time?

I wrote two shell scripts to communicate with my game server. And worked the first time I did it. Since it them they do not work anymore. Every time I do ./send.sh commands the command line hangs until I hit Ctrl+C.

It also hangs and does nothing when I do directly echo commamd > /tmp/srv-input

---

The scripts

It does start the server and configure it to read/receive my commands while it run in background:

start_czero_server.sh

#!/bin/sh

# Go to the game server application folder where the game application `hlds_run` is
cd /home/user/Half-Life
pkill -f hlds

# Set up a pipe named `/tmp/srv-input`
rm /tmp/srv-input
mkfifo /tmp/srv-input

cat > /tmp/srv-input &
echo $! > /tmp/srv-input-cat-pid

# Start the server reading from the pipe named `/tmp/srv-input`
# And also output all its console to the file `/home/user/Half-Life/my_logs.txt`
cat /tmp/srv-input | ./hlds_run -console -game czero +port 27015 > my_logs.txt 2>&1 &

# Successful execution 
exit 0

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This second script it just a wrapper which allow me easily to send commands to the my server:

send.sh

#!/bin/sh
echo "$@" > /tmp/srv-input

# Successful execution 
exit 0

Now every time I want to send a command to my server I just do on the terminal:

./send.sh mp_timelimit 30

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I always keep another open terminal open just to listen to my server server console. To do it just use the tail command with the -f flag to follow my server console output:

./tail -f /home/user/Half-Life/my_logs.txt

回答1:

You would be better off just having hlds_run read directly from the pipe instead of having cat pipe it in.

Try

./hlds_run … > my_logs.txt 2>&1 < /tmp/srv-input &

Instead of

cat /tmp/srv-input | ./hlds_run …

来源：https://stackoverflow.com/questions/42193081/why-my-named-pipe-input-command-line-just-hangs-when-it-is-called