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pidfile (3)
  • >> pidfile (3) ( FreeBSD man: Библиотечные вызовы )

  • BSD mandoc
     

    NAME

    
    
    pidfile_open
    
     
    pidfile_write
    
     
    pidfile_close
    
     
    pidfile_remove
    
     - library for PID files handling
    
     
    

    LIBRARY

    Lb libutil
    
     
    

    SYNOPSIS

       #include <sys/param.h>
       #include <libutil.h>
    struct pidfh * pidfile_open (const char *path mode_t mode pid_t *pidptr);
    int pidfile_write (struct pidfh *pfh);
    int pidfile_close (struct pidfh *pfh);
    int pidfile_remove (struct pidfh *pfh);
     

    DESCRIPTION

    The pidfile family of functions allows daemons to handle PID files. It uses flock(2) to lock a pidfile and detect already running daemons.

    The pidfile_open ();
    function opens (or creates) a file specified by the Fa path argument and locks it with the flock(2) system call. If a file can not be locked, a PID of an already running daemon is returned in the Fa pidptr argument (if it is not NULL ) The function does not write process' PID into the file here, so it can be used before fork (Ns ing);
    and exit with a proper error message when needed. If the Fa path argument is NULL /var/run/ Ao progname Ac .pid file will be used.

    The pidfile_write ();
    function writes process' PID into a previously opened file.

    The pidfile_close ();
    function closes a pidfile. It should be used after daemon fork (Ns s);
    to start a child process.

    The pidfile_remove ();
    function closes and removes a pidfile.  

    RETURN VALUES

    The pidfile_open ();
    function returns a valid pointer to a Vt pidfh structure on success, or NULL if an error occurs. If an error occurs, errno will be set. Rv -std pidfile_write pidfile_close pidfile_remove  

    EXAMPLES

    The following example shows in which order these functions should be used. Note that it is safe to pass NULL to pidfile_write (,);
    pidfile_remove ();
    and pidfile_close ();
    functions.
    struct pidfh *pfh;
    pid_t otherpid, childpid;
    
    pfh = pidfile_open("/var/run/daemon.pid", 0600, &otherpid);
    if (pfh == NULL) {
            if (errno == EEXIST) {
                    errx(EXIT_FAILURE, "Daemon already running, pid: %jd.",
                        (intmax_t)otherpid);
            }
            /* If we cannot create pidfile from other reasons, only warn. */
            warn("Cannot open or create pidfile");
    }
    
    if (daemon(0, 0) == -1) {
            warn("Cannot daemonize");
            pidfile_remove(pfh);
            exit(EXIT_FAILURE);
    }
    
    pidfile_write(pfh);
    
    for (;;) {
            /* Do work. */
            childpid = fork();
            switch (childpid) {
            case -1:
                    syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
                    break;
            case 0:
                    pidfile_close(pfh);
                    /* Do child work. */
                    break;
            default:
                    syslog(LOG_INFO, "Child %jd started.", (intmax_t)childpid);
                    break;
            }
    }
    
    pidfile_remove(pfh);
    exit(EXIT_SUCCESS);
    
     

    ERRORS

    The pidfile_open ();
    function will fail if:

    Bq Er EEXIST
    Some process already holds the lock on the given pidfile, meaning that a daemon is already running.
    Bq Er ENAMETOOLONG
    Specified pidfile's name is too long.
    Bq Er EINVAL
    Some process already holds the lock on the given pidfile, but PID read from there is invalid.
    Bq Er EAGAIN
    Some process already holds the lock on the given pidfile, but the file is truncated. Most likely, the existing daemon is writing new PID into the file.

    The pidfile_open ();
    function may also fail and set errno for any errors specified for the fstat(2), open(2), and read(2) calls.

    The pidfile_write ();
    function will fail if:

    Bq Er EDOOFUS
    Improper function use. Probably called before pidfile_open (.);

    The pidfile_write ();
    function may also fail and set errno for any errors specified for the fstat(2), ftruncate(2), and write(2) calls.

    The pidfile_close ();
    function may fail and set errno for any errors specified for the close(2) and fstat(2) calls.

    The pidfile_remove ();
    function will fail if:

    Bq Er EDOOFUS
    Improper function use. Probably called not from the process which made pidfile_write (.);

    The pidfile_remove ();
    function may also fail and set errno for any errors specified for the close(2), flock(2), fstat(2), write(2), and unlink(2) calls.  

    SEE ALSO

    flock(2), open(2), daemon(3)  

    AUTHORS

    An -nosplit The pidfile functionality is based on ideas from An John-Mark Gurney Aq [email protected] .

    The code and manual page was written by An Pawel Jakub Dawidek Aq [email protected] .


     

    Index

    NAME
    LIBRARY
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    EXAMPLES
    ERRORS
    SEE ALSO
    AUTHORS


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