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MAILOCK(3) Linux Programmer's Manual MAILOCK(3) NAME maillock, mailunlock, touchlock - manage mailbox lockfiles SYNOPSIS #include <maillock.h> cc [ flag ... ] file ... -llockfile [ library ] int maillock( const char *user, int retrycnt ); void mailunlock( void ); void touchlock( void ); DESCRIPTION The maillock function tries to create a lockfile for the users mailbox in an NFS-safe (or resistant) way. The algorithm is documented in lock- file_create(3). The mailbox is typically located in /var/mail. The name of the lockfile then becomes /var/mail/USERNAME.lock. If the environment variable $MAIL is set, and it ends with the same username as the username passed to mail- lock(), then that file is taken as the mailbox to lock instead. There is no good way to see if a lockfile is stale. Therefore if the lock- file is older then 5 minutes, it will be removed. That is why the touchlock function is provided: while holding the lock, it needs to be refreshed reg- ulary (every minute or so) by calling touchlock () . Finally the mailunlock function removes the lockfile. RETURN VALUES maillock returns one of the following status codes: #define L_SUCCESS 0 /* Lockfile created */ #define L_NAMELEN 1 /* Recipient name too long (> 13 chars) */ #define L_TMPLOCK 2 /* Error creating tmp lockfile */ #define L_TMPWRITE 3 /* Can't write pid int tmp lockfile */ #define L_MAXTRYS 4 /* Failed after max. number of attempts */ #define L_ERROR 5 /* Unknown error; check errno */ #define L_RMSTALE 8 /* Failed to remove stale lockfile */ NOTES These functions are not thread safe. If you need thread safe functions, or you need to lock other mailbox (like) files that are not in the standard location, use lockfile_create(3) instead. These functions call lockfile_create(3) to do the work. That function might spawn a set group-id executable to do the actual locking if the current process doesn't have enough priviliges. There are some issues with flushing the kernels attribute cache if you are using NFS - see the lockfile_create(3) manpage. FILES /var/mail/user.lock, /usr/lib/liblockfile.so.1 AUTHOR Miquel van Smoorenburg SEE ALSO lockfile_create(3), lockfile_touch (3), lockfile_remove(3) Linux Manpage 28 March 2001 MAILOCK(3)
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | NOTES | FILES | AUTHOR | SEE ALSO
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