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 | man pages section 3: Basic Library Functions Oracle Solaris 11 Information Library |
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| man pages section 3: Basic Library Functions Oracle Solaris 11 Information Library |
enable_extended_FILE_stdio(3C)
posix_spawnattr_getschedparam(3C)
posix_spawnattr_getschedpolicy(3C)
posix_spawnattr_getsigdefault(3C)
posix_spawnattr_getsigignore_np(3C)
posix_spawnattr_getsigmask(3C)
posix_spawnattr_setschedparam(3C)
posix_spawnattr_setschedpolicy(3C)
posix_spawnattr_setsigdefault(3C)
posix_spawnattr_setsigignore_np(3C)
posix_spawnattr_setsigmask(3C)
posix_spawn_file_actions_addclose(3C)
posix_spawn_file_actions_addclosefrom_np(3C)
posix_spawn_file_actions_adddup2(3C)
posix_spawn_file_actions_addopen(3C)
posix_spawn_file_actions_destroy(3C)
posix_spawn_file_actions_init(3C)
pthread_attr_getdetachstate(3C)
pthread_attr_getinheritsched(3C)
pthread_attr_getschedparam(3C)
pthread_attr_getschedpolicy(3C)
pthread_attr_setdetachstate(3C)
pthread_attr_setinheritsched(3C)
pthread_attr_setschedparam(3C)
pthread_attr_setschedpolicy(3C)
pthread_barrierattr_destroy(3C)
pthread_barrierattr_getpshared(3C)
pthread_barrierattr_setpshared(3C)
pthread_condattr_getpshared(3C)
pthread_condattr_setpshared(3C)
pthread_cond_reltimedwait_np(3C)
pthread_key_create_once_np(3C)
pthread_mutexattr_getprioceiling(3C)
pthread_mutexattr_getprotocol(3C)
pthread_mutexattr_getpshared(3C)
pthread_mutexattr_getrobust(3C)
pthread_mutexattr_setprioceiling(3C)
pthread_mutexattr_setprotocol(3C)
pthread_mutexattr_setpshared(3C)
pthread_mutexattr_setrobust(3C)
pthread_mutex_getprioceiling(3C)
pthread_mutex_reltimedlock_np(3C)
pthread_mutex_setprioceiling(3C)
pthread_rwlockattr_destroy(3C)
pthread_rwlockattr_getpshared(3C)
pthread_rwlockattr_setpshared(3C)
pthread_rwlock_reltimedrdlock_np(3C)
pthread_rwlock_reltimedwrlock_np(3C)
pthread_rwlock_timedrdlock(3C)
pthread_rwlock_timedwrlock(3C)
rctlblk_get_enforced_value(3C)
- database functions
#include <ndbm.h>intdbm_clearerr(DBM *db);
voiddbm_close(DBM *db);
intdbm_delete(DBM *db,datumkey);
intdbm_error(DBM *db);
datumdbm_fetch(DBM *db,datumkey);
datumdbm_firstkey(DBM *db);
datumdbm_nextkey(DBM *db);
DBM *dbm_open(const char *file,intopen_flags,mode_tfile_mode);
intdbm_store(DBM *db,datumkey,datumcontent,intstore_mode);
These functions create, access and modify a database. They maintainkey/content pairsin a database. The functions will handle large databases (up to abillion blocks) and will access a keyed item in one or twofile system accesses. This package replaces the earlierdbm library, which managed onlya single database.
keys andcontents are described by thedatum typedef. Adatum consistsof at least two members,dptr anddsize. Thedptr member pointsto an object that isdsize bytes in length. Arbitrary binary data,as well as ASCII character strings, may be stored in the objectpointed to bydptr.
The database is stored in two files. One file is a directorycontaining a bit map of keys and has.dir as its suffix. The second file contains all data and has.pag as itssuffix.
Thedbm_open() function opens a database. Thefile argument to thefunction is the pathname of the database. The function opens twofiles namedfile.dir andfile.pag. Theopen_flags argument has the same meaningas theflags argument ofopen(2) except that a database opened forwrite-only access opens the files for read and write access. Thefile_modeargument has the same meaning as the third argument ofopen(2).
Thedbm_close() function closes a database. The argumentdb must bea pointer to adbm structure that has been returned from acall todbm_open().
Thedbm_fetch() function reads a record from a database. The argumentdb is a pointer to a database structure that has been returnedfrom a call todbm_open(). The argumentkey is adatum that hasbeen initialized by the application program to the value of the keythat matches the key of the record the program is fetching.
Thedbm_store() function writes a record to a database. The argumentdb is a pointer to a database structure that has been returnedfrom a call todbm_open(). The argumentkey is adatum that hasbeen initialized by the application program to the value of the keythat identifies (for subsequent reading, writing or deleting) the record the programis writing. The argumentcontent is adatum that has been initializedby the application program to the value of the record the program iswriting. The argumentstore_mode controls whetherdbm_store() replaces any pre-existing recordthat has the same key that is specified by thekey argument. The application program must setstore_mode to eitherDBM_INSERT orDBM_REPLACE. If the database contains a record that matches thekey argument andstore_mode isDBM_REPLACE, the existing record is replaced with the new record. If the database contains a record that matches thekey argument andstore_mode isDBM_INSERT, the existing record is not replaced with the newrecord. If the database does not contain a record that matches thekey argument andstore_mode is eitherDBM_INSERT orDBM_REPLACE, the new recordis inserted in the database.
Thedbm_delete() function deletes a record and its key from the database. The argumentdb is a pointer to a database structure thathas been returned from a call todbm_open(). The argumentkey is adatum that has been initialized by the application program to the valueof the key that identifies the record the program is deleting.
Thedbm_firstkey() function returns the first key in the database. Theargumentdb is a pointer to a database structure that has beenreturned from a call todbm_open().
Thedbm_nextkey() function returns the next key in the database. Theargumentdb is a pointer to a database structure that has beenreturned from a call todbm_open(). Thedbm_firstkey() function must be called beforecallingdbm_nextkey(). Subsequent calls todbm_nextkey() return the next key until allof the keys in the database have been returned.
Thedbm_error() function returns the error condition of the database. Theargumentdb is a pointer to a database structure that has beenreturned from a call todbm_open().
Thedbm_clearerr() function clears the error condition of the database. Theargumentdb is a pointer to a database structure that has beenreturned from a call todbm_open().
These database functions support key/content pairs of at least 1024 bytes.
Thedbm_store() anddbm_delete() functions return0 when they succeed and anegative value when they fail.
Thedbm_store() function returns1 if it is called with aflagsvalue ofDBM_INSERT and the function finds an existing record with thesame key.
Thedbm_error() function returns0 if the error condition is not setand returns a non-zero value if the error condition is set.
The return value ofdbm_clearerr() is unspecified .
Thedbm_firstkey() anddbm_nextkey() functions return a keydatum. When the endof the database is reached, thedptr member of the key isa null pointer. If an error is detected, thedptr member ofthe key is a null pointer and the error condition of thedatabase is set.
Thedbm_fetch() function returns a contentdatum. If no record in thedatabase matches the key or if an error condition has been detectedin the database, thedptr member of the content is a nullpointer.
Thedbm_open() function returns a pointer to a database structure. Ifan error is detected during the operation,dbm_open() returns a (DBM *)0.
No errors are defined.
The following code can be used to traverse the database:
for(key = dbm_firstkey(db); key.dptr != NULL; key = dbm_nextkey(db))
Thedbm_ functions provided in this library should not be confused inany way with those of a general-purpose database management system. Thesefunctions do not provide for multiple search keys per entry, they donot protect against multi-user access (in other words they do not lock recordsor files), and they do not provide the many other useful databasefunctions that are found in more robust database management systems. Creatingand updating databases by use of these functions is relatively slow becauseof data copies that occur upon hash collisions. These functions are usefulfor applications requiring fast lookup of relatively static information that is tobe indexed by a single key.
Thedptr pointers returned by these functions may point into static storagethat may be changed by subsequent calls.
Thedbm_delete() function does not physically reclaim file space, although it doesmake it available for reuse.
After callingdbm_store() ordbm_delete() during a pass through the keys bydbm_firstkey() anddbm_nextkey(), the application should reset the database by callingdbm_firstkey()before again callingdbm_nextkey().
Example 1 Using the Database Functions
The following example stores and retrieves a phone number, using the nameas the key. Note that this example does not include errorchecking.
#include <ndbm.h>#include <stdio.h>#include <fcntl.h>#define NAME "Bill"#define PHONE_NO "123-4567"#define DB_NAME "phones"main(){ DBM *db; datum name = {NAME, sizeof (NAME)}; datum put_phone_no = {PHONE_NO, sizeof (PHONE_NO)}; datum get_phone_no; /* Open the database and store the record */ db = dbm_open(DB_NAME, O_RDWR | O_CREAT, 0660); (void) dbm_store(db, name, put_phone_no, DBM_INSERT); /* Retrieve the record */ get_phone_no = dbm_fetch(db, name); (void) printf("Name: %s, Phone Number: %s\n", name.dptr, get_phone_no.dptr); /* Close the database */ dbm_close(db); return (0);}Seeattributes(5) for descriptions of the following attributes:
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ar(1),cat(1),cp(1),tar(1),open(2),netconfig(4),attributes(5),standards(5)
The.pag file will contain holes so that its apparent size maybe larger than its actual content. Older versions of the UNIX operatingsystem may create real file blocks for these holes when touched. Thesefiles cannot be copied by normal means (cp(1),cat(1),tar(1),ar(1))without filling in the holes.
The sum of the sizes of akey/content pair must not exceedthe internal block size (currently 1024 bytes). Moreover allkey/content pairs thathash together must fit on a single block.dbm_store() will return anerror in the event that a disk block fills with inseparable data.
The order of keys presented bydbm_firstkey() anddbm_nextkey() depends on ahashing function.
There are no interlocks and no reliable cache flushing; thus concurrent updatingand reading is risky.
The database files (file.dir andfile.pag) are binary and are architecture-specific (forexample, they depend on the architecture's byte order.) These files arenot guaranteed to be portable across architectures.
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