CODEWITHSUNDEEP
clinuxsyslog
Noel
Noel

Reputation: 3980

C multiple write access to a log file (linux env)

I have a set of independent programs that I wrote in C. I would like all of them to write their log to the same file. Obviously comes the issue of control access. Two or more of them could end up writing simultaneously.

What is the most pragmatic way to achieve this?

I came across solutions using pthread/mutexes/etc but that sounds overkill implementation for something like that.

I am also looking at syslog but wonder if this is really for the purpose of what I need to do?

I feel that I need a daemon service taking the message and control when they are written. I wonder if that already exists.

Upvotes: 1

Views: 67

Answers (2)

Tom's
Tom's

Reputation: 2506

You have two way :

First : Using something that already exist. For the logging part, syslog (and syslog-ng) are well-know and well-used.

From that point, you can parametre syslog-ng to listen to an ip connection, and scan a dir for new file.

Your program can, when they will want to log, either connect to syslogng directly and send the log, and if the connection fail, write a new file in the directory that syslogng watch. That allow to not have the loss of the log is syslog-ng are interrupted for a reason or another.

Second : Develop something really similar to syslog-ng. In that case, it's up to you.

Upvotes: 0

Serge Ballesta
Serge Ballesta

Reputation: 149095

I am also looking at syslog but wonder if this is really for the purpose of what I need to do?

Yes

I feel that I need a daemon service taking the message and control when they are written. I wonder if that already exists.

It exists in the Unix derivatives (including Linux) and is called... syslogd

More seriously, the syslog function is intended to pass a message to a syslogd daemon that will route it according to its configuration file. Most common uses include writing it down to a file or to the system console (specially for panic level messages when nobody can be sure whether the file system is still accessible). The syslog system may come with more features than what you are asking for, but it is an extremely robust and extensively tested piece of software. In addition, it is certainly already active on your system, so you should have a strong reason to roll your own instead of using it.

Upvotes: 1

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