libslack(msg) - message module
#include <slack/std.h>
#include <slack/msg.h>
typedef struct Msg Msg;
typedef void msg_out_t(void *data, const void *mesg, size_t mesglen);
typedef int msg_filter_t(void **mesgp, const void *mesg, size_t mesglen);
typedef void msg_release_t(void *data);
Msg *msg_create(int type, msg_out_t *out, void *data, msg_release_t *destroy);
Msg *msg_create_with_locker(Locker *locker, int type, msg_out_t *out, void *data, msg_release_t *destroy);
int msg_rdlock(Msg *mesg);
int msg_wrlock(Msg *mesg);
int msg_unlock(Msg *mesg);
void msg_release(Msg *mesg);
void *msg_destroy(Msg **mesg);
void msg_out(Msg *dst, const char *format, ...);
void msg_out_unlocked(Msg *dst, const char *format, ...);
void vmsg_out(Msg *dst, const char *format, va_list args);
void vmsg_out_unlocked(Msg *dst, const char *format, va_list args);
Msg *msg_create_fd(int fd);
Msg *msg_create_fd_with_locker(Locker *locker, int fd);
Msg *msg_create_stderr(void);
Msg *msg_create_stderr_with_locker(Locker *locker);
Msg *msg_create_stdout(void);
Msg *msg_create_stdout_with_locker(Locker *locker);
Msg *msg_create_file(const char *path);
Msg *msg_create_file_with_locker(Locker *locker, const char *path);
Msg *msg_create_syslog(const char *ident, int option, int facility, int priority);
Msg *msg_create_syslog_with_locker(Locker *locker, const char *ident, int option, int facility, int priority);
Msg *msg_syslog_set_facility(Msg *mesg, int facility);
Msg *msg_syslog_set_facility_unlocked(Msg *mesg, int facility);
Msg *msg_syslog_set_priority(Msg *mesg, int priority);
Msg *msg_syslog_set_priority_unlocked(Msg *mesg, int priority);
Msg *msg_create_plex(Msg *msg1, Msg *msg2);
Msg *msg_create_plex_with_locker(Locker *locker, Msg *msg1, Msg *msg2);
int msg_add_plex(Msg *mesg, Msg *item);
int msg_add_plex_unlocked(Msg *mesg, Msg *item);
Msg *msg_create_filter(msg_filter_t *filter, Msg *mesg);
Msg *msg_create_filter_with_locker(Locker *locker, msg_filter_t *filter, Msg *mesg);
const char *msg_set_timestamp_format(const char *format);
int msg_set_timestamp_format_locker(Locker *locker);
int syslog_lookup_facility(const char *facility);
int syslog_lookup_priority(const char *priority);
const char *syslog_facility_str(int spec);
const char *syslog_priority_str(int spec);
int syslog_parse(const char *spec, int *facility, int *priority);This module provides general messaging functions. Message channels can be created that send messages to a file descriptor, a file, syslog or a client defined message handler or that multiplexes messages to any combination of the above. Messages sent to files are timestamped using (by default) the strftime(3) format: "%Y%m%d %H:%M:%S".
It also provides functions for parsing syslog targets, converting between syslog facility names and codes, and converting between syslog priority names and codes.
Msg *msg_create(int type, msg_out_t *out, void *data, msg_release_t *destroy)Creates a Msg object initialised with type, out, data and destroy. Client-defined message handlers must specify a type greater than 5. It is the caller's responsibility to deallocate the new Msg with msg_release(3) or msg_destroy. It is strongly recommended to use msg_destroy(3), because it also sets the pointer variable to null. On success, returns the new Msg object. On error, returns null.
Msg *msg_create_with_locker(Locker *locker, int type, msg_out_t *out, void *data, msg_release_t *destroy)Equivalent to msg_create(3) except that multiple threads accessing the new Msg will be synchronised by locker.
int msg_rdlock(Msg *mesg)Claims a read lock on mesg (if mesg was created with a Locker). This is needed when multiple read-only msg(3) module functions need to be called atomically. It is the caller's responsibility to call msg_unlock(3) after the atomic operation. The only functions that may be called on mesg between calls to msg_rdlock(3) and msg_unlock(3) are any read-only msg(3) module functions whose name ends with _unlocked. On success, returns 0. On error, returns an error code.
int msg_wrlock(Msg *mesg)Claims a write lock on mesg.
Claims a write lock on mesg (if mesg was created with a Locker). This is needed when multiple read/write msg(3) module functions need to be called atomically. It is the caller's responsibility to call msg_unlock(3) after the atomic operation. The only functions that may be called on mesg between calls to msg_rdlock(3) and msg_unlock(3) are any msg(3) module functions whose name ends with _unlocked. On success, returns 0. On error, returns an error code.
int msg_unlock(Msg *mesg)Unlocks a read or write lock on mesg obtained with msg_rdlock(3) or msg_wrlock(3) (if mesg was created with a Locker). On success, returns 0. On error, returns an error code.
void msg_release(Msg *mesg)Releases (deallocates) mesg and its internal data.
void *msg_destroy(Msg **mesg)Destroys (deallocates and sets to null) *mesg. Returns null.
void msg_out(Msg *dst, const char *format, ...)Sends a message to dst. format is a printf(3)-like format string. Any remaining arguments are processed as in printf(3).
Warning: Do not under any circumstances ever pass a non-literal string as the format argument unless you know exactly how many conversions will take place. Being careless with this is a very good way to build potential security vulnerabilities into your programs. The same is true for all functions that take a printf()-like format string as an argument.
msg_out(dst, buf); // EVIL
msg_out(dst, "%s", buf); // GOODvoid msg_out_unlocked(Msg *dst, const char *format, ...)Equivalent to msg_out(3) except that dst is not read-locked.
void vmsg_out(Msg *dst, const char *format, va_list args)Sends a message to dst. format is a printf(3)-like format string. args is processed as in vprintf(3).
void vmsg_out_unlocked(Msg *dst, const char *format, va_list args)Equivalent to vmsg_out(3) except that dst is not read-locked.
Msg *msg_create_fd(int fd)Creates a Msg object that sends messages to file descriptor fd. It is the caller's responsibility to deallocate the new Msg with msg_release(3) or msg_destroy(3). On success, returns the new Msg object. On error, returns null.
Msg *msg_create_fd_with_locker(Locker *locker, int fd)Equivalent to msg_create_fd(3) except that multiple threads accessing the new Msg will be synchronised by locker.
Msg *msg_create_stderr(void)Creates a Msg object that sends messages to standard error. It is the caller's responsibility to deallocate the new Msg with msg_release(3) or msg_destroy(3). It is strongly recommended to use msg_destroy(3), because it also sets the pointer variable to null. On success, returns the new Msg object. On error, returns null.
Msg *msg_create_stderr_with_locker(Locker *locker)Equivalent to msg_create_stderr(3) except that multiple threads accessing the new Msg will be synchronised by locker.
Msg *msg_create_stdout(void)Creates a Msg object that sends messages to standard output. It is the caller's responsibility to deallocate the new Msg with msg_release(3) or msg_destroy(3). It is strongly recommended to use msg_destroy(3), because it also sets the pointer variable to null. On success, returns the new Msg object. On error, returns null.
Msg *msg_create_stdout_with_locker(Locker *locker)Equivalent to msg_create_stdout(3) except that multiple threads accessing the new Msg will be synchronised by locker.
Msg *msg_create_file(const char *path)Creates a Msg object that sends messages to the file specified by path. It is the caller's responsibility to deallocate the new Msg with msg_release(3) or msg_destroy(3). It is strongly recommended to use msg_destroy(3), because it also sets the pointer variable to null. On success, returns the new Msg object. On error, returns null with errno set appropriately.
Msg *msg_create_file_with_locker(Locker *locker, const char *path)Equivalent to msg_create_file(3) except that multiple threads accessing the new Msg will be synchronised by locker.
Msg *msg_create_syslog(const char *ident, int option, int facility, int priority)Creates a Msg object that sends messages to syslog initialised with ident, option, facility and priority. It is the caller's responsibility to deallocate the new Msg with msg_release(3) or msg_destroy(3). It is strongly recommended to use msg_destroy(3), because it also sets the pointer variable to null. On success, returns the new Msg object. On error, returns null with errno set appropriately.
Msg *msg_create_syslog_with_locker(Locker *locker, const char *ident, int option, int facility, int priority)Equivalent to msg_create_syslog(3) except that multiple threads accessing the new Msg will be synchronised by locker.
Msg *msg_syslog_set_facility(Msg *mesg, int facility)Sets the facility field in mesg's data to facility. On success, returns mesg. On error, returns null with errno set appropriately.
Msg *msg_syslog_set_facility_unlocked(Msg *mesg, int facility)Equivalent to msg_syslog_set_facility(3) except that mesg is not write-locked.
Msg *msg_syslog_set_priority(Msg *mesg, int priority)Sets the priority field in mesg's data to priority. On success, returns mesg. On error, returns null with errno set appropriately.
Msg *msg_syslog_set_priority_unlocked(Msg *mesg, int priority)Equivalent to msg_syslog_set_priority(3) except that mesg is not write-locked.
Msg *msg_create_plex(Msg *msg1, Msg *msg2)Creates a Msg object that multiplexes messages to msg1 and msg2. Further Msg objects may be added to its list using msg_add_plex(3). It is the caller's responsibility to deallocate the new Msg with msg_release(3) or msg_destroy(3). It is strongly recommended to use msg_destroy(3), because it also sets the pointer variable to null. On success, returns the new Msg object. On error, returns null with errno set appropriately.
Msg *msg_create_plex_with_locker(Locker *locker, Msg *msg1, Msg *msg2)Equivalent to msg_create_plex(3) except that multiple threads accessing the new Msg will be synchronised by locker.
int msg_add_plex(Msg *mesg, Msg *item)Adds item to the list of Msg objects multiplexed by mesg. On success, returns 0. On error, returns -1 with errno set appropriately.
int msg_add_plex_unlocked(Msg *mesg, Msg *item)Equivalent to msg_add_plex(3) except that mesg is not write-locked.
Msg *msg_create_filter(msg_filter_t *filter, Msg *mesg)Creates a Msg object that sends messages to mesg after filtering messages through the filter function which must dynamically create a modified version of its input message which will be deallocated by its caller. It is the caller's responsibility to deallocate the new Msg with msg_release(3) or msg_destroy(3). It is strongly recommended to use msg_destroy(3), because it also sets the pointer variable to null. On success, returns the new Msg object. On error, returns null with errno set appropriately.
Msg *msg_create_filter_with_locker(Locker *locker, msg_filter_t *filter, Msg *mesg)Equivalent to msg_create_filter(3) except that multiple threads accessing the new Msg will be synchronised by locker.
const char *msg_set_timestamp_format(const char *format)Sets the strftime(3) format string used when sending messages to a file. By default, it is "%Y%m%d %H:%M:%S ". On success, returns the previous format string. On error, returns null with errno set appropriately.
int msg_set_timestamp_format_locker(Locker *locker)Sets the locking strategy for changing the timestamp format used when sending messages to a file. This is only needed if the timestamp format will be modified in multiple threads. On success, returns 0. On error, returns -1 with errno set appropriately.
int syslog_lookup_facility(const char *facility)Returns the code corresponding to facility. If not found, returns -1.
int syslog_lookup_priority(const char *priority)Returns the code corresponding to priority. If not found, returns -1.
const char *syslog_facility_str(int spec)Returns the name corresponding to the facility part of spec. If not found, returns null.
const char *syslog_priority_str(int spec)Returns the name corresponding to the priority part of spec. If not found, returns null.
int syslog_parse(const char *spec, int *facility, int *priority)Parses spec as a facility.priority string. If facility is non-null, the parsed facility is stored in the location pointed to by facility. If priority is non-null the parsed priority is stored in the location pointed to by priority. On success, returns 0. On error, returns -1 with errno set appropriately.
These are the supported syslog facility and priority names and their corresponding symbolic constants:
syslog facilities syslog priorities
---------------------- -----------------------
"kern" LOG_KERN "emerg" LOG_EMERG
"user" LOG_USER "alert" LOG_ALERT
"mail" LOG_MAIL "crit" LOG_CRIT
"daemon" LOG_DAEMON "err" LOG_ERR
"auth" LOG_AUTH "warning" LOG_WARNING
"syslog" LOG_SYSLOG "info" LOG_INFO
"lpr" LOG_LPR "debug" LOG_DEBUG
"news" LOG_NEWS
"uucp" LOG_UUCP
"cron" LOG_CRON
"local0" LOG_LOCAL0
"local1" LOG_LOCAL1
"local2" LOG_LOCAL2
"local3" LOG_LOCAL3
"local4" LOG_LOCAL4
"local5" LOG_LOCAL5
"local6" LOG_LOCAL6
"local7" LOG_LOCAL7On error, errno is set by underlying functions or as follows:
EINVALAn argument was null, or could not be parsed.
MT-Disciplined - msg functions - See locker(3) for details.
MT-Safe - syslog functions
Parse syslog facility priority pair:
#include <slack/std.h>
#include <slack/msg.h>
int main(int ac, char **av)
{
int facility, priority;
if (syslog_parse(av[1], &facility, &priority) != -1)
syslog(facility | priority, "syslog(%s)", av[1]);
return EXIT_SUCCESS;
}Multiplex a message to several locations:
#include <slack/std.h>
#include <slack/msg.h>
int main(int ac, char **av)
{
Msg *stdout_msg = msg_create_stdout();
Msg *stderr_msg = msg_create_stderr();
Msg *file_msg = msg_create_file("/tmp/junk");
Msg *syslog_msg = msg_create_syslog("ident", 0, LOG_DAEMON, LOG_ERR);
Msg *plex_msg = msg_create_plex(stdout_msg, stderr_msg);
msg_add_plex(plex_msg, file_msg);
msg_add_plex(plex_msg, syslog_msg);
msg_out(plex_msg, "Multiplex message\n");
unlink("/tmp/junk");
return EXIT_SUCCESS;
}libslack(3), err(3), prog(3), openlog(3), syslog(3), locker(3)
20230824 raf <raf@raf.org>