userdb_read(3)

NAME

userdb_read(), userdb_write(), userdb_delete() — read, write or delete information in the user database, /var/adm/userdb

SYNOPSIS

#include <prot.h> 

int userdb_read(const char *name, const char * const attr[], 
                char * const value[]); 

int userdb_write(const char *name, const char * const attr[], 
                 const char * const value[]); 

int userdb_delete(const char *name); 

DESCRIPTION

These functions read, write, or delete information in the user database, /var/adm/userdb, which is described in userdb(4).

For element i of the two arrays, attr[i] is a pointer to the name of an attribute, and value[i] is a pointer to its value represented as text. The arrays attr and value are terminated by a null character.

userdb_read() reads the values of the attributes specified in the attr array from the user database into the corresponding value array. If an attribute is not present, a null string is copied into the value array. Each element (except for the terminating null) of the value array is a pointer to a buffer. The size of each buffer is assumed to be at least USERDB_MAX_ATTR_SIZE bytes, which is defined in <prot.h>.

userdb_write() writes the values of the attributes specified in the attr array from the corresponding value array into the database. For each null string in the value array, the corresponding attribute is deleted; the system-wide default described in /etc/default/security will then apply; see security(4). Attribute values are allowed to contain only printable ASCII characters (hex 20-7e).

The tab character (hex 09) may also be used for the following special cases for value:

\t+num
\t-num: Add or subtract num to or from the current attribute value. Both num and the current value are assumed to be a string of at most nine ASCII decimal digits. The current value may also have an optional sign, and is assumed to have a value of 0 if the attribute is not defined.
\t: No operation (do not modify the attribute).

userdb_delete() deletes a user entry from the database. The user entry contains all of the configurable and internal attributes for a user.

RETURN VALUE

0: success
1: invalid user
2: invalid argument
3: insufficient permission to access the user database
4: file system error
5: invalid attribute
6: invalid attribute value
7: block overflow
8: entry overflow
9: database lock failure
10: database is disabled; see userdb(4)

EXAMPLES

The following program segment writes values for two attributes into the user database for user joe, and then deletes a third attribute. It then reads and prints two attributes plus the attribute which it removed. Finally, it removes all of the attributes for user amy.

#include <prot.h>

char p1[USERDB_MAX_ATTR_SIZE]; 
char p2[USERDB_MAX_ATTR_SIZE]; 
char p3[USERDB_MAX_ATTR_SIZE]; 

char *write_attrs[] = { 
         "AUDIT_FLAG", "MIN_PASSWORD_LENGTH", "AUTH_MAXTRIES", 0 }; 
char *write_values[] = { "1", "7", "", 0 }; 
char *read_attrs[]  = { 
         "MIN_PASSWORD_LENGTH", "AUTH_MAXTRIES", "AUDIT_FLAG", 0 }; 
char *read_values[]  = { p1, p2, p3, 0 }; 

if (userdb_write("joe", write_attrs, write_values)) 
    exit(1); 
if (userdb_read("joe", read_attrs, read_values)) 
    exit(2); 
printf ("p1=%s p2=%s p3=%s", p1, p2, p3); 
userdb_delete("amy"); 

After successful execution, the output is:

p1=7 p2= p3=1 

FILES

/var/adm/userdb: user database
/etc/default/security: security defaults configuration file
/etc/security.dsc: security attributes description file

userdb_read(3)

Technical documentation

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