cc [flag . . . ] file . . . -lgen [library] . . .#include <shadow.h>
struct spwd
getspent (void);
struct spwd
getspnam (const char
name);
int lckpwdf (void);
int ulckpwdf (void);
void setspent (void);
void endspent (void);
struct spwd
fgetspent (FILE
fp);
setspent- rewind shadow password file for repeated searches
fgetspent- return pointer to next spwd structure in stream
endspent- close the shadow password file
lckpwdf- lock password file
ulckpwdf- unlock password file
The getspent and getspnam routines each return a pointer to an object with the following structure containing the broken-out fields of a line in the /etc/shadow file. Each line in the file contains a ``shadow password'' structure, declared in the shadow.h header file:
struct spwd{ charsp_namp; char
sp_pwdp; long sp_lstchg; long sp_min; long sp_max; long sp_warn; long sp_inact; long sp_expire; unsigned long sp_flag; };
The
getspent
routine when first called returns a pointer to the first
spwd structure in the file;
thereafter, it returns a pointer to the next spwd structure in the file;
so successive calls can
be used to search the entire file.
The
getspnam
routine searches from the beginning of the
file until a login name matching
name
is found, and returns a pointer to the particular structure
in which it was found.
The getspent and getspnam routines
populate the sp_min
, sp_max
, sp_lstchg
,
sp_warn
, sp_inact
, or sp_expire
field with -1
or the sp_flag
field with 0
if the corresponding field in /etc/shadow is empty.
If an end-of-file is encountered on reading, these functions
return a NULL pointer.
If a read error occurs, these functions return a NULL pointer
and errno is set to indicate the error.
If there is a format error in the file, a NULL pointer is
returned and errno is set to EINVAL.
/etc/security/ia/.pwd.lock is the lock file. It is used to coordinate modification access to the password files /etc/passwd and /etc/shadow. lckpwdf and ulckpwdf are routines that are used to gain modification access to the password files, through the lock file. A process first uses lckpwdf to lock the lock file, thereby gaining exclusive rights to modify the /etc/passwd or /etc/shadow password file. Upon completing modifications, a process should release the lock on the lock file via ulckpwdf. This mechanism prevents simultaneous modification of the password files.
lckpwdf attempts to lock the file /etc/security/ia/.pwd.lock within 15 seconds. If unsuccessful, for example, /etc/security/ia/.pwd.lock is already locked, it returns -1. If successful, a return code other than -1 is returned.
ulckpwdf attempts to unlock the file /etc/security/ia/.pwd.lock. If unsuccessful, for example, /etc/security/ia/.pwd.lock is already unlocked, it returns -1. If successful, it returns 0.
A call to the setspent routine has the effect of rewinding the shadow password file to allow repeated searches. The endspent routine may be called to close the shadow password file when processing is complete.
The fgetspent routine returns a pointer to the next spwd structure in the stream fp, which matches the format of /etc/shadow.
All information is contained in a static area, so it must be copied if it is to be saved.