CODEWITHSUNDEEP
linuxbashshellredis
Eddie Deng
Eddie Deng

Reputation: 1479

make redis server ignore Ctrl+C when launched from shell script

I want to use shell script to launch Redis server and then monitor a log file:

#!/bin/bash
/path/to/redis/src/redis-server &
tail -f /path/to/log/logfile.log

If I run this script and press Ctrl+C from the terminal, the tail -f terminated, which is what I want, however the Redis also detected SIGINT and exited.

I tried to write the script like this:

 #!/bin/bash
 trap '' INT TSTP
 ~/redis/src/redis-server &
 tail -f ./script1

This time things go even worse, the tail -f refused to terminate while Redis still detected SIGINT and exited.

It seems that there is some problems specific to Redis regarding ignoring signals.

My goal is to make tail -f responds to Ctrl+C while making Redis ignore this signal.

Please anyone tell me whether this can be achieved and if so, give me some advice?

Upvotes: 0

Views: 569

Answers (1)

Mark Plotnick
Mark Plotnick

Reputation: 10271

redis-server catches SIGINT (Ctrl+C), even if SIGINT was being ignored. This is an unusual choice; most software will check and won't catch SIGINT if it's already being ignored.

When it receives SIGINT, it saves the database and shuts down.

If you start it as a service, it won't be associated with any terminal at all, and won't see any Ctrl+C you type.

If you start it as a background job in an interactive shell:

$ /path/to/redis/src/redis-server &

your shell will put it into a process group that is different from the terminal's process group, and typing Ctrl+C won't affect it. (If you bring it to the foreground with fg, Ctrl+C will send SIGINT to the program).

But, when you run a script like this:

#!/bin/bash
/path/to/redis/src/redis-server &
tail -f /path/to/log/logfile.log

the shell that runs the script will be non-interactive, and any program that it starts in the background (with &) will be in the same process group as the shell. So if you run that shell script in the foreground, typing Ctrl+C will send SIGINT to the shell, to redis-server, and to tail.

To prevent Ctrl+C from sending SIGINT to redis-server in a case like this, you need to either put redis-server in its own process group or disassociate it from your terminal. You can do this with setsid, which does both:

#!/bin/bash
setsid /path/to/redis/src/redis-server &
tail -f /path/to/log/logfile.log

Upvotes: 1

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