open_limit.c

[詳解]

/*++
/* NAME
/*  open_limit 3
/* SUMMARY
/*  set/get open file limit
/* SYNOPSIS
/*  #include <iostuff.h>
/*
/*  int open_limit(int limit)
/* DESCRIPTION
/*  The \fIopen_limit\fR() routine attempts to change the maximum
/*  number of open files to the specified limit.  Specify a null
/*  argument to effect no change. The result is the actual open file
/*  limit for the current process. The number can be smaller or larger
/*  than the requested limit.
/* DIAGNOSTICS
/*  open_limit() returns -1 in case of problems. The errno
/*  variable gives hints about the nature of the problem.
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

/* System libraries. */

#include "sys_defs.h"
#include <sys/time.h>
#include <sys/resource.h>
#include <errno.h>

#ifdef USE_MAX_FILES_PER_PROC
#include <sys/sysctl.h>
#define MAX_FILES_PER_PROC      "kern.maxfilesperproc"
#endif

/* Application-specific. */

#include "iostuff.h"

 /*
  * 44BSD compatibility.
  */
#ifndef RLIMIT_NOFILE
#ifdef RLIMIT_OFILE
#define RLIMIT_NOFILE RLIMIT_OFILE
#endif
#endif

/* open_limit - set/query file descriptor limit */

int     open_limit(int limit)
{
#ifdef RLIMIT_NOFILE
    struct rlimit rl;
#endif

    if (limit < 0) {
    errno = EINVAL;
    return (-1);
    }
#ifdef RLIMIT_NOFILE
    if (getrlimit(RLIMIT_NOFILE, &rl) < 0)
    return (-1);
    if (limit > 0) {

    /*
     * MacOSX incorrectly reports rlim_max as RLIM_INFINITY. The true
     * hard limit is finite and equals the kern.maxfilesperproc value.
     */
#ifdef USE_MAX_FILES_PER_PROC
    int     max_files_per_proc;
    size_t  len = sizeof(max_files_per_proc);

    if (sysctlbyname(MAX_FILES_PER_PROC, &max_files_per_proc, &len,
             (void *) 0, (size_t) 0) < 0)
        return (-1);
    if (limit > max_files_per_proc)
        limit = max_files_per_proc;
#endif
    if (limit > rl.rlim_max)
        rl.rlim_cur = rl.rlim_max;
    else
        rl.rlim_cur = limit;
    if (setrlimit(RLIMIT_NOFILE, &rl) < 0)
        return (-1);
    }
    return (rl.rlim_cur);
#endif

#ifndef RLIMIT_NOFILE
    return (getdtablesize());
#endif
}