FAM(3X) FAM(3X)
fam - File Alteration Monitor (FAM) library routines
#include <fam.h>
extern int FAMOpen(FAMConnection* fc);
extern int FAMClose(FAMConnection* fc);
extern int FAMMonitorDirectory(FAMConnection *fc,
char *filename,
FAMRequest* fr,
void* userData);
extern int FAMMonitorFile(FAMConnection *fc,
char *filename,
FAMRequest* fr,
void* userData);
int FAMSuspendMonitor(FAMConnection *fc, FAMRequest *fr);
int FAMResumeMonitor(FAMConnection *fc, FAMRequest *fr);
int FAMCancelMonitor(FAMConnection *fc, FAMRequest *fr);
int FAMNextEvent(FAMConnection *fc, FAMEvent *fe);
int FAMPending(FAMConnection* fc);
typedef struct {
int fd;
} FAMConnection;
#define FAMCONNECTION_GETFD(fc) (fc->fd)
typedef struct {
int reqnum;
} FAMRequest;
enum FAMCodes { FAMChanged=1, FAMDeleted=2, FAMStartExecuting=3,
FAMStopExecuting=4, FAMCreated=5, FAMMoved=6, FAMAcknowledge=7,
FAMExists=8, FAMEndExist=9 };
typedef struct {
FAMConnection* fc;
FAMRequest fr;
char hostname[MAXHOSTNAMELEN];
char filename[NAME_MAX];
void *userdata;
FAMCodes code;
} FAMEvent;
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FAM(3X) FAM(3X)
extern int FAMErrno;
extern char *FamErrlist[];
FAM monitors files and directories, notifying interested applications of
changes. Routines for communicating with the fam(1M) server process are
found in ``libfam.a'', which is loaded if the option ``-lfam'' is used
with cc(1) or ld(1). The library ``libC.a'' (``-lC'') must also be
specified.
An application calls routines described here to establish a list of files
for fam to monitor. Fam generates events on a socket to communicate with
the application. The fam process is started when the first connection
from any application to it is opened. It exits after all connections to
it have been closed.
Here are the steps required to use FAM in an application:
1. Create a connection to fam by calling FAMOpen. This routine will
pass back a FAMConnection structure used in all fam procedures.
2. Tell fam which files and directories to monitor by calling
FAMMonitorFile and FAMMonitorDirectory to express interest in files
and directories, respectively.
3. Select on the fam socket file descriptor and call FAMPending when
the fam socket is active, and FAMNextEvent when FAMPending indicates
that an event is available. Alternatively, call FAMPending (or
FAMNextEvent) periodically to check the socket connection to fam to
see if any new information has arrived. If there are no events
pending, FAMNextEvent blocks until an event occurs.
4. When the application is through monitoring a file or directory, it
should call FAMCancelMonitor. If the application wants to
temporarily suspend monitoring of a file or directory, it may call
FAMSuspendMonitor. When the application is ready to start
monitoring again, it calls FAMResumeMonitor.
5. Before the application exits, it should call FAMClose to free
resources associated with files still being monitored and to close
the connection to fam.
The FAMConnection Structure
The FAMConnection data structure is created when opening a connection to
FAM. Subsequently it is passed into all FAM procedures. This structure
has all the information in it to communicate to fam.
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FAM(3X) FAM(3X)
Use the macro FAMCONNECTION_GETFD to access the file descriptor inside
the FAMConnection, rather than accessing it directly.
The FAMRequest Structure [Toc] [Back]
When fam is called on to monitor a file, it passes back a FAMRequest
structure. This structure uniquely identifies the request so that it may
be cancelled, using FAMCancelMonitor or suspended, using
FAMSuspendMonitor.
The FAMEvent Structure [Toc] [Back]
Changes to files and directories are encoded in the FAMEvent structure.
The code field of this structure contains one of the following
enumeration constants:
FAMChanged
Some value which can be obtained with fstat(1) changed for a
file or directory being monitored.
FAMDeleted
A file or directory being monitored was deleted or its name was
changed. This event is also generated when monitoring starts on
a nonexistent file or directory.
FAMStartExecuting
An executable file or shared library being monitored started
executing. If multiple processes execute the same file, this
event only occurs when the first process starts.
FAMStopExecuting
An executable file being monitored which was running finished.
If multiple processes from an executable are running, this event
is only generated when the last one finishes.
FAMCreated
A file was created in a directory being monitored. Note: this
event is only generated for files created directly in a
directory being monitored; subdirectories are not automatically
monitored.
FAMMoved FAMMoved events never occur. The name remains defined so that
programs that reference it will still compile.
FAMAcknowledge
After a FAMCancelMonitor, fam generates a FAMAcknowledge event.
Also, if an invalid pathname is specified, fam generates a
FAMAcknowledge event.
FAMExists
When the application requests a file be monitored, fam generates
a FAMExists event for that file. When the application requests
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FAM(3X) FAM(3X)
a directory be monitored, fam generates a FAMExists event for
that directory and every file directly contained in that
directory.
FAMEndExist
When the application requests a file directory be monitored, a
series of FAMExists events is generated as described above.
After the last FAMExists message, fam generates a FAMEndExist
message.
If a FAM event applies to a file or directory being monitored, the
FAMEvent's filename field contains the full pathname that was passed to
fam. If an event applies to an entry in a monitored directory, the
filename field contains the relative path only. For example, if the
directory /usr/tmp/xyzzy were monitored, and the file
/usr/tmp/xyzzy/plugh were deleted, a FAMDeleted event would be generated
containing "plugh" in filename. If the directory itself were deleted,
filename would contain "/usr/tmp/xyzzy".
FAMOpen, FAMClose
The application opens a connection to fam by calling FAMOpen. FAMOpen
initializes the FAMConnection structure passed in to it and returns 0 if
successful, otherwise -1. The variable char* appName should be set to
the name of your application. The FAMConnection structure is passed to
all subsequent FAM procedure calls.
FAMClose frees resources associated with files still being monitored and
closes a fam connection. It returns 0 if successful and -1 otherwise.
FAMMonitorDirectory, FAMMonitorFile
FAMMonitorDirectory and FAMMonitorFile tell FAM to start monitoring a
directory or file, respectively. The parameters to this function are a
FAMConnection (initialized by FAMOpen), a FAMRequest structure, a
filename and a user data pointer. The FAMRequest structure is modified
to subsequently identify this request. When the file or directory
changes, a FAM event structure will be generated. The application can
retrieve this structure by calling FAMNextEvent (see description under
FAMNextEvent).
FAMMonitorDirectory monitors changes that happens to the contents of the
directory (as well as the directory file itself); FAMMonitorFile monitors
only what happens to a particular file. Both routines return 0 if
successful and -1 otherwise.
The filename argument must be a full pathname.
FAMSuspendMonitor, FAMResumeMonitor
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FAM(3X) FAM(3X)
FAMSuspendMonitor temporarily suspends monitoring of files or
directories. This is useful when an application is not displaying
information about files, when it is iconified, for example.
FAMResumeMonitor signals fam to start monitoring the file or directory
again. Changes which occur while monitoring is suspended are enqueued
and delivered when monitoring is resumed.
Both of these routines take a FAMConnection and a FAMRequest structure.
The FAMRequest Structure is returned from the FAMMonitorFile or
FAMMonitorDirectory routines and return 0 if successful and -1 otherwise.
Because fam runs as an asynchronous process, FAMNextEvent may return a
few events regarding a given request after that request has been
suspended.
FAMCancelMonitor [Toc] [Back]
When an application is through monitoring a file or directory, it should
call FAMCancelMonitor. This routine will signal fam not to monitor this
directory anymore. The FAMRequest structure is returned from the
FAMMonitorFile or FAMMonitorDirectory routines. FAMCancelMonitor returns
0 if successful and -1 otherwise.
FAMPending, FAMNextEvent
FAMPending returns 1 if an event is waiting and 0 if no event is waiting.
It also returns 1 if an error has been encountered. This routine returns
immediately to the caller.
FAMNextEvent will get the next FAM event. If there are no FAM events
waiting, then the calling application blocks until a FAM event is
received. If blocking is not desirable, call FAMPending before
FAMNextEvent, and only call FAMNextEvent when FAMPending says an event is
available.
There are two ways to for applications to receive FAM events:
1. The Select approach - The application selects on the file
descriptor returned from FAMOpen, in the FAMConnection structure.
When this file descriptor becomes active, the application calls
FAMPending to determine whether a complete event is ready, and
FAMNextEvent to retrieve the pending FAM event.
2. The Polling approach - The application calls FAMPending
periodically (usually when the system is waiting for input).
When FAMPending returns 1, the application calls FAMNextEvent to
retrieve the pending FAM event.
FAMNextEvent reads any information that is on the fam socket, and returns
it to the application in the form of a FAMEvent.
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FAM(3X) FAM(3X)
FAMNextEvent returns 1 if successful and -1 otherwise.
fam(1M).
The FAMMoved event is not currently supported.
FAMNextEvent may not initialize the FAMEvent's filename field for
FAMEndExist and FAMAcknowledge events. Use the request number to
determine the file or directory to which those events refer.
FAMErrno and FamErrlist are not set when errors occur.
When a shell script is run, notification is generated for the shell
executing the script, typically
.
Each process is limited to 1000 active requests at a time.
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