Watching new entries on Linux Syslog from a C program

Question

I want to write a program that monitors syslog and performs an action when PPP authentication fails.

I think "tail -f /var/log/syslog" could help, but I'm not sure how to use it... probably using pipes?

I have found something similar written in bash, but I'm not sure how to implement it in C.

This is the bash method:

First create a named pipe using mkfifo:

$ mkfifo -p /home/mezgani/syslog.pipe

Make syslog.conf to points to this file:

*.info |/home/mezgani/syslog.pipe

Restart syslog:

$ sudo pkill -HUP syslogd

Create processing script that read the pipe

$ cat > foo
#!/bin/bash
cat /home/mezgani/syslog.pipe | while read input
do
    # some stuff
    echo ${input}
    # ….
done

Sounds very hacky. Isn't there a PPP plugin mechanism you can use instead? — trojanfoe, Apr 21 '11 at 07:09
I did some research on linux PPP server but couldn't find anything. — capsula, Apr 21 '11 at 07:16

score 4 · Accepted Answer · answered Apr 23 '11 at 08:09

Finally I could found the solution!!

The solution was using named pipes!

First, I need to create a named pipe: mkfifo /pipe

Then, I feed the pipe with the log info: tail -f /var/log/syslog > /pipe

And then, I read the pipe from the C program using OPEN

int pipefd;
pipefd = open("/tmp/myFIFO", O_WRONLY);

score 0 · Answer 2 · answered Apr 21 '11 at 07:09

0

Try to use inotify function. Using it you can monitor if a file or directory has changed.

answered Apr 21 '11 at 07:09

Patryk

2 Answers2