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#include <shadow.h>struct spwd *getspent (void)
struct spwd *getspnam (name) char *name;
int lckpwdf (void)
int ulckpwdf (void)
void setspent (void)
void endspent (void)
struct spwd *fgetspent (fp) FILE *fp;
getspnam- get matching login name shadow password entry
setspent- rewind shadow password file to allow repeated searches
endspent- closes shadow password file when processing is complete
fgetspent- get pointer to next spwd structure
lckpwdf- lock the shadow password file
ulckpwdf- unlock the shadow 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 {
char *sp_namp;
char *sp_pwdp;
long sp_lstchg;
long sp_min;
long sp_max;
};
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'' or ``sp_lstchg'' field with -1 if the corresponding field in /etc/shadow is empty. If an end-of-file or an error is encountered on reading, or there is a format error in the file, these functions return a NULL pointer and set errno to EINVAL.
/etc/.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.
The lckpwdf routine attempts to lock the file /etc/.pwd.lock. If file /etc/.pwd.lock is already locked, lckpwdf tries for 15 seconds to lock the file. If lckpwdf is unsuccessful, then lckpwdf returns a -1. If lckpwdf succeeds to lock the file /etc/.pwd.lock within 15 seconds, then a return code other than -1 is returned.
The ulckpwdf routine attempts to unlock the file /etc/.pwd.lock. If successful, ulckpwdf returns a 0. If the unlocking failed, as in the case that file /etc/.pwd.lock was not locked initially, then ulckpwdf returns a -1.
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.
These routines are provided for compatibility purposes only, and may not function correctly on all systems. We recommend that the getprpwent(S) routines be used as an alternative.
All information is contained in a static area, so it must be copied if it is to be saved.