76 lines
1.8 KiB
C
76 lines
1.8 KiB
C
/*++
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/* NAME
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/* open_lock 3
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/* SUMMARY
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/* open or create file and lock it for exclusive access
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/* SYNOPSIS
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/* #include <open_lock.h>
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/*
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/* VSTREAM *open_lock(path, int flags, int mode, why)
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/* const char *path;
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/* int flags;
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/* int mode;
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/* VSTRING *why;
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/* DESCRIPTION
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/* This module opens or creates the named file and attempts to
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/* acquire an exclusive lock. The lock is lost when the last
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/* process closes the file.
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/*
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/* Arguments:
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/* .IP "path, flags, mode"
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/* These are passed on to safe_open().
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/* .IP why
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/* storage for diagnostics.
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/* SEE ALSO
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/* safe_open(3) carefully open or create file
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/* myflock(3) get exclusive lock on file
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/* DIAGNOSTICS
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/* In case of problems the result is a null pointer and a problem
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/* description is returned via the global \fIerrno\fR variable.
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/* LICENSE
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/* .ad
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/* .fi
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/* The Secure Mailer license must be distributed with this software.
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/* AUTHOR(S)
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/* Wietse Venema
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/* IBM T.J. Watson Research
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/* P.O. Box 704
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/* Yorktown Heights, NY 10598, USA
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/*--*/
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/* System library. */
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#include <sys_defs.h>
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#include <unistd.h>
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#include <fcntl.h>
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/* Utility library. */
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#include <msg.h>
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#include <vstream.h>
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#include <vstring.h>
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#include <safe_open.h>
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#include <myflock.h>
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#include <open_lock.h>
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/* open_lock - open file and lock it for exclusive access */
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VSTREAM *open_lock(const char *path, int flags, int mode, VSTRING *why)
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{
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VSTREAM *fp;
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/*
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* Carefully create or open the file, and lock it down. Some systems
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* don't have the O_LOCK open() flag, or the flag does not do what we
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* want, so we roll our own lock.
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*/
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if ((fp = safe_open(path, flags, mode, -1, -1, why)) == 0)
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return (0);
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if (myflock(vstream_fileno(fp), MYFLOCK_EXCLUSIVE | MYFLOCK_NOWAIT) < 0) {
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vstring_sprintf(why, "file %s: unable to lock: %m", path);
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vstream_fclose(fp);
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return (0);
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}
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return (fp);
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}
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